Fish Histology: Female Reproductive Systems

Fish Histology Fish Histology Female Reproductive Systems Donald B. McMillan Department of Biology The University of...

Author: Donald B. McMillan

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Fish Histology

Fish Histology Female Reproductive Systems

Donald B. McMillan Department of Biology The University of Western Ontario London, Ontario Canada

A C.I.P. Catalogue record for this book is available from the Library of Congress.

ISBN 978-1-4020-5415-0 (HB) ISBN 978-1-4020-5715-1 (e-book) Published by Springer, P.O. Box 17, 3300 AA Dordrecht, The Netherlands. www.springer.com

Printed on acid-free paper

All Rights Reserved © 2007 Springer No part of this work may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission from the Publisher, with the exception of any material supplied specifically for the purpose of being entered and executed on a computer system, for exclusive use by the purchaser of the work.

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/VERTHEPASTYEARSORSO THETECHNIQUESOFMICROSCOPYHAVEATTAINEDAHIGHDEGREEOFEXCELLENCERESULTINGIN THEACCUMULATIONOFMASSESOFINFORMATIONONTHEHISTOLOGYOFlSHES4HISGOLDENAGEOFDESCRIPTIVEMORPHOLOGY HOWEVER ISDRAWINGTOACLOSEANDTHETIMEISRIPETODRAWTHISMATERIALTOGETHERINAFORMTHATCANBEUSEDBY RESEARCHERSWHOARESTUDYINGTHEDIVERSEASPECTSOFTHEWORLDSDWINDLINGSTOCKSOFlSH&ORSEVERALYEARS )HAVE BEENACCUMULATINGMATERIALONlSHHISTOLOGYAND MORERECENTLY HAVEBEENCOMPILINGATEXTBOOKONTHEFEMALE REPRODUCTIVE SYSTEMS -Y AMBITION HAS BEEN TO PARALLEL THE EXCELLENT TEXTS AVAILABLE ON MAMMALIAN HISTOLOGY ANDEVENTUALLYPRODUCESIMILARVOLUMESONOTHERSYSTEMS!ShlSHv )HAVEINCLUDED!GNATHA #HONDRICHTHYES AND/STEICHTHYES.OMENCLATUREUSEDFOLLOWSTHATOFTHEAUTHORSBEINGCITEDINOTHERCASES)HAVEUSED&ISHESOF THE7ORLD NDED BY*3.ELSON PUBLISHEDBY*OHN7ILEY3ONS !LTHOUGHHISTOLOGYDEALSINVISUALIMAGES ONEOFTHEPROBLEMSTHATHASBESETTHISDISCIPLINEINTHEPASTHASBEEN THEHIGHCOSTANDDIFlCULTYOFPUBLISHINGMICROGRAPHS4HEADVENTOFDIGITALTECHNOLOGYANDTHESTORAGEOFIMAGES ONCOMPACTDISCS#$S HOWEVER HASSOLVEDTHISPROBLEMAND)HAVERESCUEDMANYCLASSICANDBEAUTIFULIMAGES FROMTHEDUSTANDOBSCURITYOFLIBRARYSTACKS MAKINGTHEMONCEAGAINREADILYAVAILABLETOTHEPRESENT DAYSCIEN TIST)HAVEEMBRACEDTHISTECHNOLOGYWITHABANDONANDLARGENUMBERSOFILLUSTRATIONSAREINCLUDEDWITHTHISWORK )TSHOULDBENOTEDTHATMAGNIlCATIONSGIVENINTHELEGENDSARETAKENFROMTHEORIGINALSOURCESTHEACTUALVALUES WILLVARYDEPENDINGONTHECOMPUTERBEINGUSED $R 7*2 ,ANZING FORMERLY OF THE 3CHOOL OF "IOLOGICAL 3CIENCES OF THE 5NIVERSITY OF 3YDNEY !USTRALIA PROVIDEDSUGGESTIONSANDENCOURAGEMENTATTHEOUTSETOFTHEPROJECT)ACKNOWLEDGE WITHGRATITUDE THEPATIENT ASSISTANCEOFMYCOLLEAGUESATTHE5NIVERSITYOF7ESTERN/NTARIO ESPECIALLYTHE$EANOF3CIENCE $R&*,ONG STAFFE ANDTHE#HAIROFTHE$EPARTMENTOF"IOLOGY $R-"&ENTON WHOMADEEXCELLENTFACILITIESAVAILABLEFORMY RESEARCH-ESSRS2*(ARRISAND)##RAIG PROVIDEDPATIENTANDGENEROUSTECHNICALASSISTANCE)AMGRATEFULTO THEOBLIGINGSTAFFOFTHE4AYLOR3CIENCE,IBRARYATTHE5NIVERSITYOF7ESTERN/NTARIOFORTHEIRCHEERFULATTENTIONTO MYNEEDS4HANKSAREOWEDTOTHEMANYAUTHORSANDPUBLISHERSWHOREADILYGAVEPERMISSIONTOCOPYTHEIRMATERIAL SPECIlCACKNOWLEDGEMENTSAREINCLUDEDWITHTHELEGENDS

IX

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THISMERELYENSURESTHATSPERMATOZOAARESHEDNEARTHE EGGS BUT MORE OFTEN IT INVOLVES INSEMINATION OF THE FEMALES)NTERNALFERTILIZATIONMAYBEFOLLOWEDIMME DIATELYBYTHELAYINGOFNEWLYFERTILIZEDEGGSORSOME TIMELATERBYTHERELEASEOFEMBRYOSATVARIOUSSTAGES OFDEVELOPMENT 6IVIPARITYISHIGHLYSPECIALIZEDINSOMEGROUPSOF ELASMOBRANCHSANDTELEOSTSANDTHEDEVELOPINGYOUNG MAYBEHOUSEDWITHINTHEOVARYORINTHEGENITALDUCTS 6IVIPAROUSSPECIESOFELASMOBRANCHSRANGEFROMINTER NALINCUBATORSTHATSIMPLYRETAINLARGE YOLKEDEGGSTO OTHERSPECIESINWHICHTHECOMPLEXITYOFPLACENTATION ANDEGGYOLKRETENTIONAPPROACHESTHEEUTHERIANCON DITION#ALLARDETAL 4HECARTILAGINOUSlSHES AREOFPARTICULARINTERESTTOREPRODUCTIVEBIOLOGISTSBE CAUSEOFTHEIRSTRUCTURALANDFUNCTIONALSIMILARITIESIN PATTERNSOFREPRODUCTIONANDDEVELOPMENTWITHTHOSE OFAMNIOTES7OURMS )NTHESEHIGHLYADVANCED ANIMALS SEVERAL PROCESSES EITHER MADE THEIR APPEAR ANCE FOR THE lRST TIME AMONG VERTEBRATES OR BECAME WELLESTABLISHEDINTERNALFERTILIZATION VIVIPARITY PLA CENTALMECHANISMSFORFOETALMAINTENANCE PATTERNSOF GENITALTRACTDEVELOPMENTANDSEXDIFFERENTIATION AND THEVERTEBRATETYPEOFREPRODUCTIVEENDOCRINOLOGY !LTHOUGHMOSTlSHAREDIOECIOUSORGONOCHORISTIC (%2-!0(2/$)4)3-DOESOCCURWHEREOVARIANANDTESTIC ULARTISSUESAPPEARINTHESAMEINDIVIDUAL!TZ 'REENWOOD #HAN AND 9EUNG 'RANDI AND #OLOMBO )T IS FOUND ESPECIALLY AMONG CYCLOSTOMESANDTELEOSTSAND INSOMESPECIES ISTHE NORMAL WAY OF LIFE -ALE AND FEMALE SEX CELLS RIPEN ATTHESAMETIMEIN 39.#(2/./53 (%2-!0(2/$)4%3)N #/.3%#54)6%(%2-!0(2/$)4%3 HOWEVER THEREISSEXRE VERSAL 02/4/'9./53 (%2-!0(2/$)4%3FUNCTIONlRSTAS FEMALES THENASMALESWHILE02/4!.$2/53(%2-!0(2/ $)4%3TRANSFORMFROMMALESINTOFEMALES 2EPRODUCTIONINMOSTlSHESISCYCLIC ALTHOUGHTHE LENGTHOFTHECYCLEISEXTREMELYVARIABLESEEREVIEWS BY 'REENWOOD 7OURMS "ILLARD AND "RETON $ODDAND3UMPTER (AMLETTAND

)NTRODUCTION

4HEREISANAMAZINGVARIATIONINMETHODSOFREPRODUC TION IN lSHES 3OME SPECIES AT LARGE OUTLAYS OF EN ERGY RELEASEENORMOUSNUMBERSOFMODERATELYYOLKY MESOLECITHAL EGGS THAT ARE SUBJECTED TO SUBSEQUENT PARENTALNEGLECT!SINGLEOCEANSUNlSH -OLAMOLA FOR EXAMPLE BY A PRODIGIOUS FEAT OF PRODUCTIVITY IS SAIDTOSPAWNOVER EGGS.ELSON /THER lSH MAY PRODUCE RELATIVELY SMALL NUMBERS OF MUCHYOLKIER TELOLECITHALEGGS OFTENIMPROVINGTHEIR CHANCES OF SURVIVAL BY PROVIDING PARENTAL SUPPORT %LABORATENEST BUILDINGACTIVITIESMAYPRECEDESEXUAL BEHAVIOUR AND PARENTAL CARE MAY CONTINUE FOR SOME TIMEAFTERHATCHING4HEYOUNGMAYBESHELTERED FOR VARYING PERIODS WITHIN THE BODY OF THE FEMALE AND EVENTHEMALE3OMEVIVIPAROUSTELEOSTSPRODUCEONLY ONETOFOURWELL DEVELOPEDYOUNGATATIME4HIBAULT AND3CHULTZ !NAMAZINGARRAYOFSTRUCTURALAD APTATIONSHASEVOLVEDFORTHEPROTECTIONANDNOURISH MENTOFTHESEDEVELOPINGYOUNG !REMARKABLEREPRODUCTIVESTRATEGYISSEENINBIT TERLINGS #YPRINIDAE !CHEILOGNATHINAE WHERE PAR ENTSTRANSFERRESPONSIBILITYFORTHECAREOFTHEIRYOUNG TO A FRESHWATER UNIONID MUSSEL !LDRIDGE 4HEFEMALEBITTERLINGEXTENDSHERLONGOVIPOSITORINTO THEMANTLECAVITYOFTHEMUSSELANDDEPOSITSHEREGGS BETWEEN THE GILL lLAMENTS 4HE MALE THEN EJECTS HIS SPERM INTO THE MUSSELS INHALENT WATER CURRENT AND FERTILIZATION TAKES PLACE WITHIN THE GILLS OF THE HOST %ARLY DEVELOPMENTAL STAGES ARE PROTECTED FROM THE RISKOFPREDATIONWITHINTHEBODYOFTHEMUSSELSUB SEQUENTLYTHELARVAESWIMAWAYFROMTHEHOSTTOCON TINUELIFEONTHEIROWN !LTHOUGHEXTERNALFERTILIZATIONISUSUALAMONGlSH ES COPULATIONMAYOCCURINSOMESPECIES3OMETIMES

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+OOB 3OME LIKETHELAMPREYSANDCERTAINSAL MONIDANDEELSPECIES SPAWNONLYONCEANDTHENDIE OTHERSMAYBREEDEVERYTWOORTHREEYEARS BUTMOST BREED ONCE OR SEVERAL TIMES A YEAR 3OME HAGlSHES SOME TELEOSTS AND SOME SPECIES OF OVIPAROUS SKATES APPEARTOBREEDTHROUGHOUTTHEYEAR 4HE APPEARANCE OF THE OVARY OF CYCLICAL BREEDERS VARIESGREATLYATDIFFERENTTIMESOFTHECYCLEANDTHREE OVARIAN TYPES HAVE BEEN RECOGNIZED ON THE BASIS OF THEPATTERNOFOOCYTEDEVELOPMENT7ALLACEAND3EL MAN .AGAHAMA &ISH THAT SPAWN ONCE AND THEN DIE AS LAMPREYS ANADROMOUS SALMON SPE CIES /NCORHYNCHUS SPP OR CATADROMOUS EELS !N GUILLA SPP HAVE 39.#(2/./53 /6!2)%3 IN WHICH ALL OOCYTES ARE AT THE SAME STAGE OF DEVELOPMENT 3PE CIESTHATGENERALLYSPAWNONCEPERYEARDURINGASHORT BREEDING SEASON DISPLAY '2/50 39.#(2/./53 /6!2)%3 WITH AT LEAST TWO POPULATIONS OF OOCYTES AT DIFFERENT DEVELOPMENTALSTAGESTHISISTHECOMMONESTSITUATION IN TELEOSTS /VULATION OF GROUP SYNCHRONOUS OVARIES MAYOCCURATINTERVALSOVERTHEBREEDINGSEASONSOTHAT THEOOCYTESARERELEASEDINhBATCHESv4HEYELLOWTAIL mOUNDER 0LEURONECTES FERRUGINEUS OF THE CONTINENTAL SHELF OF THE WESTERN .ORTH !TLANTIC IS SUCH A "!4#( 30!7.%2-ANNINGAND#RIM !N!39.#(2/./53 /6!29 CONTAINS OOCYTES AT ALL STAGES OF DEVELOPMENT ANDOCCURSINSPECIESTHATSPAWNMANYTIMESDURINGA LONGBREEDINGSEASONEG MEDAKA/RYZIASSPP KIL LIlSH &UNDULUSHETEROCLITUS ANDGOLDlSH #ARASSIUS AURATUS -ANYlSH INBOTHTEMPERATEANDTROPICALREGIONS EXHIBIT AN ANNUAL RHYTHM OF REPRODUCTION THAT IS CORRELATED WITH PHOTOPERIOD AND TEMPERATURE VARIA TIONSINTHETROPICSTHEINCREASEDPRODUCTIVITYOFTHE RAINYSEASONISALSOANINmUENCE"ILLARDAND"RETON 4HEBREEDINGSEASONSOFMARINETELEOSTSOFTHE NORTHERN HEMISPHERE ARE CHARACTERISTICALLY SHORTER IN NORTHERNTOMONTHS THANINSOUTHERNFORMSTO MONTHS 1ASIM /OCYTESINTHENORTHERNSPE CIESDEVELOPSYNCHRONOUSLYANDAREPROBABLYRELEASED INASINGLESPAWNINGTHEREISAWIDERANGEINSIZESOF MATURINGOOCYTESINASYNCHRONOUSOVARIESOFSOUTHERN SPECIES INDICATING THAT SEVERAL SPAWNINGS OCCUR IN A SINGLE SEASON 4HE APPEARANCE OF CONTINUOUS BREED ING HOWEVER MAYBEDECEPTIVEINTHATINDIVIDUALSOR POPULATIONS MAY EXHIBIT SYNCHRONIZED ANNUAL REPRO DUCTIVECYCLESTHATARESIMPLYOUTOFPHASEWITHONE ANOTHER3COTT

/RIGINOFTHE'ENITAL3YSTEMS

/VARIES AND TESTES DEVELOP FROM PAIRED MASSES OF MESODERMALTISSUEONEITHERSIDEOFTHEDORSALMESEN TERYINTHEDORSOLATERALLININGOFTHEPERITONEALCAVITY &IGURE 4HESE INDIFFERENT '%.)4!, 2)$'%3 BULGE INTO THE DEVELOPING COELOM AND ARE LATER INVADED BY 02)-/2$)!, '%2- #%,,3 THAT WILL EVENTUALLY GIVE RISE TOOOGONIAORSPERMATOGONIA.IEUWKOOPAND3UTAS URYA .AKAMURAETAL #OVERINGTHESUR FACEOFTHEOVARYISTHESO CALLED '%2-).!,%0)4(%,)5- WHICH IS CONTINUOUS WITH THE PERITONEUM LINING THE COELOM&IGURE $URINGEMBRYONICDEVELOPMENT THEGERMINALEPITHELIUMISTHEPROLIFERATIVELAYERTHAT GIVES RISE TO MUCH OF THE SOMATIC TISSUE OF THE RUDI MENTARY GONAD )N THE COMMON SNOOK #ENTROPOMUS UNDECIMALIS OOGONIAAREDISTRIBUTEDAMONGTHESTRATI lEDSQUAMOUSCELLSOFTHISEPITHELIUMTHEYPROLIFER ATE BY MITOSIS AND SINK INTO THE STROMA OF THE OVARY WHERE FURTHER DEVELOPMENT TAKES PLACE &IGURE 'RIER 0RESUMABLYTHEGERMCELLSHAVEINVAD EDTHEEPITHELIUMFROMANEXTERNALSOURCE3INCEITIS NOTKNOWNATTHISTIMEWHETHERTHISEPITHELIUMISTHE SOURCEOFGERMCELLSINALLlSH SOMEAUTHORSCONSIDER ITMISLEADINGTOREFERTOITASAhGERMINALEPITHELIUMv PREFERRINGTHETERMh'/.!$!,%0)4(%,)5-vFORTHISPRO LIFERATIVELAYER.IEUWKOOPAND3UTASURYA )N MOST VERTEBRATES THE SOMATIC TISSUE OF EACH GONADHASADOUBLEORIGIN DEVELOPINGFROMTWODIS TINCTBUTCLOSELYASSOCIATEDMESENCHYMALSOURCESTHE #/24%8 IS DERIVED FROM PROLIFERATION OF THE COELOMIC EPITHELIUM AND IS DESTINED TO BECOME AN OVARY THE -%$5,,! COMES FROM A MORE MEDIAL CELLULAR PROLIF ERATIONANDPRODUCESTHETESTIS7OURMS 7OLFF 5SUALLY ONE OF THESE PORTIONS GROWS RAPIDLY WHILETHEOTHERFAILSTODEVELOPANDTHESEXOFTHEIN DIVIDUALISDETERMINEDEARLY4HISPATTERNOFGONADAL DIFFERENTIATIONFROMTWOCOMPONENTSISCHARACTERISTIC OF ELASMOBRANCHS AND ALL TETRAPODS #HIEFl )N CONTRAST BOTH MALE AND FEMALE GONADS OF CYCLO STOMES AND TELEOSTS DEVELOP DIRECTLY FROM COELOMIC EPITHELIUM THAT CORRESPONDS TO THE CORTEX OF OTHER VERTEBRATES 7OLFF AND THERE APPEARS TO BE NO CONTRIBUTION FROM MEDULLARY TISSUE $ODD AND 3UMPTER )THASBEENSUGGESTEDTHATTHESEDIF FERENCESMAYACCOUNTFORTHEWIDESPREADOCCURRENCE

4HEPHENOMENONOFSEXUALDIFFERENTIATIONHASBEENDISCUSSEDAT LENGTHBY,EPORI

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OF INTERSEXUALITY AMONG CYCLOSTOMES AND TELEOSTS (OAR 0RIMORDIAL GERM CELLS ARISE EARLY IN DEVELOPMENT WITHIN EMBRYONIC ENDODERM OR MESODERM LONG BE FORE THE RUDIMENTS OF THE GONADS ARE FORMED AND AT A DISTANCE FROM THE SITE THEY WILL EVENTUALLY OCCUPY &IGUREL 4HEIRSITEOFORIGINISEXTRAGONADALAND INSOMElSHES MAYBEEXTRAEMBRYONIC4HEYMIGRATE INTOTHERUDIMENTARYGONADANDESTABLISHRESIDENCEIN THEOUTERMARGINOFTHESTROMA JUSTBENEATHTHEGONAD ALEPITHELIUM&IGURE 7OURMS .IEUWKOOP AND3UTASURYA (AMAGUCHI 4IMMERMANS AND4AVERNE 'EVERSETAL VAN7INKOOP ETAL 'RANDIAND#OLOMBO ,ATER THEY WILLBEENSHEATHEDBYCELLSDERIVEDFROMTHEGONADAL EPITHELIUM &IGURE )N CONTRAST TO OTHER SPECIES WHERE PRIMORDIAL GERM CELLS MIGRATE TO PREVIOUSLY FORMEDGERMINALRIDGES THEPRIMORDIALGERMCELLSOF THECARP#YPRINUSCARPIOAREPRESENTATTHESITEOFTHE GONADALRIDGESBEFOREAGONADALANLAGEAPPEARS0AR MENTIERAND4IMMERMANS 6ARIOUS MECHANISMS HAVE BEEN PROPOSED TO EX PLAIN THE MIGRATION OF PRIMORDIAL GERM CELLS IN lSH AMOEBOID MOVEMENTS OF THE GERM CELLS THEMSELVES A PASSIVE DELIVERANCE PRODUCED BY MORPHOGENETIC MOVEMENTS OF THE SURROUNDING TISSUES AND TRANSPORT IN THE BLOODSTREAM -IGRATION IS SAID TO BE POWERED BY AMOEBOID MOVEMENT IN LARGEMOUTH BLACK BASS -ICROPTERUS SALMOIDES SALMOIDES *OHNSTON ANDTHECARP#YPRINUSCARPIO.EDELEAAND3TEOPOE WHILE IN THE MEDAKA /RYZIAS LATIPES (AMA GUCHI ANDBARBEL"ARBUSCONCHONIUS4IMMER MANSAND4AVERNE MORPHOGENETICMOVEMENTS OFTHESURROUNDINGTISSUESARETHOUGHTTOPROVIDETHE MOTIVE FORCE 3UGGESTIONS OF A VASCULAR ROUTE OF MI GRATIONHAVERECEIVEDNORECENTSUBSTANTIATION 0RIMORDIALGERMCELLSAREMITOTICALLYACTIVEASTHEY BECOME SEGREGATED FROM SOMATIC CELLS BUT MITOSIS CEASESDURINGTHEPERIODOFMIGRATIONTOTHEGONADAL PRIMORDIA (AMAGUCHI 0ARMENTIER AND 4IM MERMANS 4IMMERMANS AND 4AVERNE 'RANDIAND#OLOMBO )NSOMESPECIESASECOND PROLIFERATIVEPHASEOCCURSSOONAFTERGONADALCOLONI ZATION BUT IN OTHERS THERE MAY BE A PERIOD OF WEEKS OR MONTHS OF INTRAGONADAL MITOTIC REST INTRAGONADAL PRIMORDIAL GERM CELLS OF THE CARP #YPRINUS CARPIO FOREXAMPLE REMAINhMITOTICALLYSILENTvFORANEXTEND EDPERIODMAKINGTHEMESPECIALLYSUITABLEFORSTUDIES BEFORETHEONSETOFPROLIFERATIONVAN7INKOOP ETAL

0RIMORDIAL GERM CELLS ARE LARGER THAN SURROUNDING CELLS ARE ROUNDED OVAL OR PEAR SHAPED AND SHOW A DISTINCTCELLBOUNDARY&IGURE .EDELEAAND3TEO POE (OGAN .IEUWKOOPAND3UTASURYA (AMAGUCHI 0ARMENTIERAND4IMMERMANS 4IMMERMANSAND4AVERNE VAN7INKOOP ET AL 'RANDI AND #OLOMBO 4HE LARGE NUCLEUSHASADISTINCTMEMBRANEANDISOFTENECCEN TRIC IT CONTAINS ONE OR TWO PROMINENT NUCLEOLI 4HE CYTOPLASMISOFTENHOMOGENEOUSBUT DEPENDINGUPON THESTAGEOFDEVELOPMENTANDTHESPECIESBEINGSTUD IED ITMAYCONTAINYOLKGRANULES OILDROPLETS ORPIG MENT GRANULES 'RANULAR ENDOPLASMIC RETICULUM AND ABUNDANTRIBOSOMESHAVEBEENDESCRIBEDINTHECYTO PLASMOFSOMESPECIESANDANACTIVE'OLGICOMPLEXIS FOUNDINSOMECELLS OFTENNEARCLUMPSOFMITOCHON DRIA&IGURE #OATEDVESICLES SUGGESTIVEOFMETA BOLICEXCHANGESWITHTHEGONADALENVIRONMENT WERE DESCRIBEDINTHECYTOPLASMOFPRIMORDIALGERMCELLSOF THECARP#YPRINUSCARPIO OFTENNEARTHESURFACEMEM BRANE&IGURE VAN7INKOOPETAL 4WOCYTOPLASMICMARKERSOFUNCERTAINSIGNIlCANCE ARESAIDTODISTINGUISHPRIMORIDALGERMCELLSOF/RY ZIASLATIPESFROMSOMATICCELLS 3(%%43 /& !'2!.5,!2 %.$/0,!3-)# 2%4)#5,5-ANDELECTRON DENSE -)4/#(/. $2)!, !33/#)!4%$ '2!.5,!2 -!4%2)!, &IGURE (OGAN 4HE FENESTRATED SHEETS OF AGRANULAR ENDOPLASMIC RETICULUM PERHAPS PRODUCED BY BLEB BING OF THE NUCLEAR ENVELOPE FOLLOW THE CONTOURS OF THENUCLEI SOMETIMESALMOSTENCIRCLINGTHEM)NTHE GERMCELLSOFMANYSPECIES MITOCHONDRIALASSOCIATED GRANULAR MATERIAL FORMS ONE OR TWO COMPACT MASSES THATHAVEBEENDESIGNATEDVARIOUSLYAS "!,")!.) "/$ )%3 0%2).5#,%!2 .5!'%3 0%2).5#,%!2 $%.3% "/$)%3 AND '%2-).!, $%.3% "/$)%3 4IMMERMANS AND 4AV ERNE VAN 7INKOOP ET AL 'RANDI AND #OLOMBO 4HEYARELOOSELY WOVENANDSTRAND LIKEINPREMIGRATORYGERMINALCELLSOF/RYZIASLATIPES THIS APPEARANCE GRADUALLY CHANGES AS THE CELLS BEGIN THEIRMIGRATIONAND INTHEGONADALANLAGEN THESEBOD IES ARE AMORPHOUS OF VARIOUS SIZES AND SHAPES AND COMPOSEDOFELECTRON DENSE lNElBRILS&IGURE (AMAGUCHI )NTHECARP#YPRINUSCARPIOTHEY INCREASEINSIZEWITHDEVELOPMENTANDPARTOFTHEMA TERIALBECOMESMOREELECTRONDENSETHESEDARKMASSES ADHERETOMITOCHONDRIAANDMAYBECENTRESFORMITO CHONDRIALMULTIPLICATION&IGURE VAN7INKOOP ETAL

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4HEFEMALEGENITALSYSTEMCONSISTSOFTHE/6!2)%3THAT PRODUCE %''3OR /6!AND INMOSTSPECIES ADUCTSYS TEMCOMMUNICATINGWITHTHEEXTERIOR)NADDITIONTOITS CYTOCRINEFUNCTIONOFPRODUCINGFERTILIZABLEGAMETES THE OVARY SHARES WITH THE TESTIS THE COMPLEMENTARY ENDOCRINE FUNCTION OF SECRETING A VARIETY OF STEROID HORMONESTHATREGULATEDEVELOPMENTOFTHEGERMCELLS /VIDUCTSMAYBESIMPLEPASSAGEWAYSFORTHEEGGSBUT OFTEN THEIR LINING IS GLANDULAR AND FORMS PROTECTIVE COVERINGS FOR THE EGGS )N SOME VIVIPAROUS SPECIES YOUNG MAY DEVELOP WITHIN THE OVARY AND IN OTHERS WITHINTHEOVIDUCTS 'ONADSOFVERTEBRATESALWAYSORIGINATEFROMBILAT ERALPRIMORDIA BUTMANYSPECIESPOSSESSONLYONEGO NADASADULTS&RANCHI -ANDL AND:UCKERMAN (ARDER )NHAGlSH THELEFTGONADDEGENERATES ANDONLYTHERIGHTDEVELOPSINLAMPREYS THETWOPRI MORDIA FUSE DURING DEVELOPMENT FORMING A SINGLE MIDLINEGONAD/VARIESOFELASMOBRANCHSDEVELOPAS PAIREDSTRUCTURESALONGTHEDORSALWALLOFTHECOELOM ON EACH SIDE OF THE MIDLINE 7OURMS $ODD $ODDAND3UMPTER #ALLARDETAL (AMLETTAND+OOB )NSEVERALSPECIES EITHERTHE RIGHTORLEFTOVARYFAILSTOMATURE4HEFUNCTIONALOVARY MAYBETHERIGHTASINSEVERALVIVIPAROUSSHARKS OR THE LEFT SOME VIVIPAROUS RAYS IN SOME OVIPAROUS SKATES HOWEVER BOTHOVARIESAREFUNCTIONAL!TROPHY OFTHEOVIDUCTMAYOCCURONTHESAMESIDEASTHENON FUNCTIONALOVARY4HEREISARANGEINTELEOSTlSHESFROM COMPLETE FUSION TO PARTIAL FUSION INVOLVING ONLY THE POSTERIORPARTOFTHEGONADORJUSTTHEGONODUCTS&RAN CHI -ANDL AND :UCKERMAN (ARDER 3OMETIMESONEOFTHEGONADSISRUDIMENTARYORMERELY SMALLERBUTSTILLPRESENT 4HE OVARIES ARE SUSPENDED IN THE POSTERIOR BODY CAVITY DORSAL TO THE GUT BY -%3/6!2)! THAT RUN THEIR ENTIRELENGTH&IGURE (ARDER 4HEOVARIES MAYBEDISPLACEDTOWARDTHEINTESTINE COMINGTOLIE WITHTHEINTESTINEWITHINTHEMESENTERY&IGURE "ENEATH THE 6)3#%2!, 0%2)4/.%5- THAT ENVELOPS EACH OVARY IS A CAPSULE OF CONNECTIVE TISSUE AND SMOOTH MUSCLE THE45.)#!!,"5').%!4HE/6!2)!.!24%29AR RIVESBYWAYOFTHEMESOVARIUMANDBRANCHESREPEAT EDLYINTOTHETUNICAALBUGINEA 4HE OVARIES OF CYCLOSTOMES MOST ELASMOBRANCHS ANDSOMETELEOSTSARESOLIDANDOVAARESHEDDIRECTLY INTOTHEBODYCAVITY.ODUCTSYSTEMISPRESENTINCY CLOSTOMES AND THE EGGS ARE EXPELLED FROM THE BODY

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4HE VERTEBRATE OVARY IS AN AGGREGATION OF DEVELOP ING&/,,)#,%3ENMESHEDINAVASCULAR342/-!OFLOOSE CONNECTIVETISSUEANDENCLOSEDWITHINANENVELOPEOF GONADALEPITHELIUM&IGURE 4HESTROMACONSISTS OF COLLAGENOUS ELASTIC AND RETICULAR lBRES AND BE COMESGREATLYDISTENDEDASTHEFOLLICLESENLARGE/NLY IN A SPENT OVARY WHEN THE STROMA IS COLLAPSED IS IT EASILYSEEN"ENEATHTHEOVARIANENVELOPE ACONDEN SATION OF STROMAL TISSUE FORMS THE 45.)#! !,"5').%! ACAPSULEOFCONNECTIVETISSUEAND SOMETIMES SMOOTH MUSCLE &IGURE #OLLAGENOUS AND ELASTIC lBRES ARE MOST ABUNDANT IN THE PERITONEUM LESS SO IN THE

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CULAR THECA INTERNA AND AVASCULAR THECA EXTERNA &OL LICULOGENESIS IS CONSIDERED TO BE CONCLUDED WHEN THEBASEMENTMEMBRANECOMPLETELYENCLOSESTHEFOL LICULAREPITHELIUMTHETHECALLAYERSMAYBEFRAGMEN TARYATTHISTIME%NSCONCEDWITHINTHEOVARIANSTROMA THEFOLLICLECONTINUESITSDEVELOPMENT )NTHEPASTITHASBEENPROPOSEDTHATOOGONIAAND EARLY MEIOTIC STAGES ARE NOT PRESENT IN THE OVARIES OF ADULT CARTILAGINOUS lSHES )T HAS BEEN SHOWN THAT OOGENESIS OCCURS EARLY IN THE LIFE OF THE SPOTTED RAY 4ORPEDO MARMORATA AN APLACENTAL VIVIPAROUS ELAS MOBRANCH WITH A REPRODUCTIVE CYCLE OF THREE YEARS 0RISCO 2ICCHIARI AND!NDREUCCETTI 4HE SITE OFORIGINANDMIGRATORYROUTEOFTHEPRIMORDIALGERM CELLSWASNOTDETERMINED#LUSTERSOFOOGONIAANDEARLY MEIOTICOOCYTESWEREOBSERVEDINTHEGONADALANLAGE OFEMBRYOSGERMCELLSINTHECLUSTERSWERECONNECTED BYINTERCELLULARBRIDGESBORDEREDBYANELECTRON DENSE MEMBRANEABOUTNMTHICK&IGURE )NOVARIES OFSUBADULTANDADULTFEMALES HOWEVER ALLTHEGERM CELLS WERE ORGANIZED INTO FOLLICLES AND NO CLUSTERS OF OOGONIA OR EARLY MEIOTIC CELLS WERE FOUND WITH A SINGLEEXCEPTION)NONEADULTFEMALE THEPERSISTENCE OFGERMCELLSNOTORGANIZEDINTOFOLLICLESMAYSUPPORT THE CONCEPT OF hREPRODUCTIVE PLASTICITYv AND REPRE SENT THE VARIATION THAT IS TARGETED BY NATURAL SELEC TION THEREBYACCOUNTINGFORTHEDIFFERENTREPRODUCTIVE STRATEGIESADOPTEDBYCARTILAGINOUSlSHES )N LAMPREYS PRIMARY GERM CELLS DIVIDE SLOWLY IN THEGONADALRIDGEBENEATHTHEPERITONEUM,EWISAND -C-ILLAN (ARDISTY 4HISISFOLLOWEDBY APERIODOFMORERAPIDDIVISIONWHENTHEGERMCELLS FORM '%2- #%,, .%343ORCYSTS-EIOTICPROPHASEBE GINSINBOTHISOLATEDGERMCELLSANDINTHECELLNESTS #ELLSFROMTHEPERITONEALEPITHELIUMGIVERISETOFOL LICULAR ELEMENTS 'ERM CELLS MAY BEGIN CYTOPLASMIC GROWTHORUNDERGODEGENERATIONATRESIA INEARLYSTAG ESOFMEIOTICPROPHASE/OGENESISOCCURSTOSOMEEX TENTINMOSTORALLLAMPREYGONADS)NGONADSDESTINED TO BECOME OVARIES OOGENESIS IS MORE SYNCHRONOUS THANINTESTESAND EVENTUALLY ONLYOOCYTESAREPRESENT )NMALELAMPREYS OOCYTESTHATHAVEPROCEEDEDTOTHE CYTOPLASMIC GROWTH PHASE ARE ELIMINATED BY ATRESIA SOTHATTHETESTISBECOMESSMALLERDURINGDIFFERENTIA TIONANDCONTAINSONLYSMALLNUMBERSOFRESIDUALGERM CELLSATMETAMORPHOSISTHESEDEVELOP BYMITOSIS INTO NESTSOFPRIMARYSPERMATOGONIA $IVISION OF DEVELOPING GERM CELLS IN THE OVARIES OF LAMPREYS CAUSES EVAGINATIONS OF THE OVARIAN WALL TOEXPANDVENTRALLY SUBDIVIDINGTHEOVARYINTOLOBES

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CELLS&IGURE 0OLARITYISLAIDDOWNWITHINTHEOOCYTEOFTHEME DAKA/RYZIASLATIPESDURINGFORMATIONOFTHEZONAPEL LUCIDA BEFOREYOLKPRODUCTIONBEGINS)WAMATSUAND .AKASHIMA 4HIS!.)-!, 6%'%4!,!8)3CONSISTS OFAN !.)-!, 0/,%OFTHEMOSTACTIVEPROTOPLASMTHAT DEVELOPS DIAMETRICALLY OPPOSITE A 6%'%4!, 0/,% OF YOLKY RELATIVELYINERTPROTOPLASM)TISSUGGESTEDTHAT THISAXISISESTABLISHEDDURINGDEVELOPMENTBYRECIPRO CALINTERACTIONSOFTHEOOCYTEWITHTHEADJACENTFOLLICU LARCELLSWHEREAGROUPOFCOMPACTLYCLUSTEREDFOLLICULAR CELLSDETERMINESTHEPOSITIONOFTHEVEGETALPOLEAREA !FOLLICULARCELLATTHEOPPOSITESIDEOFTHEOOCYTEDIF FERENTIATESINTOA-)#2/09,!2#%,, THEREBYDETERMINING THEPOSITIONOFTHE-)#2/09,%POINTOFSPERMENTRY AT THEANIMALPOLE)NDEED THEMICROPYLEISACONVENIENT MARKERFORIDENTIFYINGTHEANIMALPOLE )NLAMPREYS POSSIBLYALLELASMOBRANCHS ANDSOME BONY lSHES OOGONIAL PROLIFERATION IS LIMITED TO THE LARVAL OR EMBRYONIC PERIOD 4OKARZ 3UCCES SIVE GENERATIONS OF OOCYTES APPEAR TO DEVELOP FROM OOGONIAINTHEGERMINALRIDGEOFADULTHAGlSH-YXINE GLUTINOSA THESE OOCYTES ENTER A RESTING PHASE WHILE THEYAWAITOVULATIONOFTHEPREVIOUSGENERATIONOFOO CYTES 0ATZNER )N MOST BONY lSHES OOGONIAL PROLIFERATIONISFOUNDINTHEADULTANIMAL4HEREISA LIMITED PERIOD OF PEAK OOGONIAL DIVISION IN SPECIES WITHCIRCUMSCRIBEDANNUALBREEDINGCYCLESINSPECIES WHICHDONOTHAVERESTRICTEDBREEDINGCYCLES OOGONIAL PROLIFERATION OCCURS EITHER IN WAVES OR CONTINUOUSLY THROUGHOUTTHEYEAR !TTHEENDOFOOGONIALPROLIFERATION THESECONDARY OOGONIABECOMEPRIMARYOOCYTESANDENTERAPROTRACT EDEARLYPROPHASE!PRIMARYOOCYTEISSURROUNDEDBY ASINGLELAYEROFFOLLICULARCELLSTOFORMA 02)-/2$)!, &/,,)#,%4OKARZ 4HISPROCESSISSIMILARINALL NON MAMMALIAN VERTEBRATES AND BEGINS AT APPROXI MATELYTHESAMESTAGEOFMEIOTICPROPHASE!SCHEME OF FOLLICULAR DEVELOPMENT IN THE MEDAKA /RYZIAS LATIPESISSHOWNIN&IGURE

)NTRODUCTION

/OGONIA PROLIFERATE BY MITOSIS TO BECOME 02)-!29 //#94%3)NTHESECELLSTHECHROMOSOMESAREARRESTED IN THE DIPLOTENE STAGE OF THE lRST MEIOTIC PROPHASE 4HE OOCYTES THEN ENTER A PERIOD OF GROWTH THAT VARIES FROM SPECIES TO SPECIES ENLARGING CHIEmY BY ACCUMULATINGYOLK!STHEYGROWANDMATURE VARIOUS INTRACELLULARANDEXTRACELLULARCHANGESOCCUR)NITIALLY THEFOLLICULARCELLSFORMASIMPLESQUAMOUSEPITHELIUM AROUND EACH OOCYTE BUT AS DEVELOPMENT PROCEEDS THECELLSENLARGEANDMAYBECOMECUBOIDALANDEVEN COLUMNAR)NCYCLOSTOMESANDTELEOSTSTHE &/,,)#5,!2 %0)4(%,)5-REMAINSSINGLELAYEREDBUT IN#HONDRICH THYES ITMAYBECOMPOSEDOFSEVERALLAYERS&RANCHI !S IS TYPICAL OF MANY EPITHELIA DESMOSOMES CONNECTADJACENTFOLLICULARCELLS&OLLICULARCELLSMAY ALSO PRODUCE OVARIAN HORMONES 4HE FOLLICULAR EPI THELIUMISSURROUNDEDBYITSOWNBASALLAMINAWHICH SEPARATESITFROMASHEATHOFCONDENSEDVASCULARCON NECTIVETISSUE THE4(%#!&/,,)#5,)!STHEFOLLICLEDIF FERENTIATES THETHECABECOMESMOREDISTINCTANDMAY BE DIVIDED INTO A 4(%#! ).4%2.! AND 4(%#! %84%2.! 4HETHECACONTAINSlBROBLASTS COLLAGENOUSlBRESAND CAPILLARIESAND INSOMESPECIES SPECIALTHECALSTEROID PRODUCINGCELLS&IGURE $URINGDEVELOPMENT ATHICK TRANSLUCENT ACELLULAR :/.! 0%,,5#)$! OR 6)4%,,).% %.6%,/0% DEVELOPS BE TWEENTHEOOCYTEANDFOLLICULARCELLS!FTERHATCHING WHENASIMPLEPLASMAMEMBRANEWOULDBEINADEQUATE FORSUCHALARGECELLTOWITHSTANDTHERIGOURSOFINDE PENDENT EXISTENCE THIS SHEATH SERVES AS A TOUGH EN CLOSUREFORTHEEGG%VENINVIVIPAROUSFORMS WHERE THE EMBRYOS DEVELOP WITHIN THE BODY OF THE FEMALE THIS ENVELOPE IS FORMED DURING OOGENESIS &LEGLER $URING GROWTH OF THE OOCYTE THE ZONA PELLU CIDABECOMESPERFORATEDBY 0/2% #!.!,3 ENABLINGAN EXCHANGEOFMATERIALSBETWEENTHEOOCYTEANDFOLLICU LARCELLSTHESECHANNELSCONTAINMICROVILLITHATEXTEND FROMTHESURFACESOFBOTHTHEOOCYTEANDTHEFOLLICULAR

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"ECAUSEOFTHEACCESSIBLITYOFINITIALSTAGESINTHE SYNGNATHIDSTHEPIPElSHANDTHESEAHORSEEXTEN SIVEDESCRIPTIONSOFFOLLICULOGENESISHAVEBEENCARRIED OUTONTHESESPECIES PROVIDINGMUCHOFTHEINFORMA TIONUSEDHERE"EGOVACAND7ALLACE 3EL MAN 7ALLACE AND0LAYER 4HEIRGERMINALRIDGE ISWELL DElNEDANDCONTAINS //'/.)! %!2,9 02/0(!3% )//#94%3 AND3/-!4)#02%&/,,)#5,!2#%,,3ASWELLAS OCCASIONALDEGENERATINGCELLS&IGURE /OGONIAOF THE GERMINAL RIDGE DIVIDE BY MITOSIS!S THE DAUGH TER CELLS MOVE AWAY THEY ARE ENVELOPED BY &/,,)#5 ,!2 #%,,3WHICHAREDERIVEDFROMTHEPROLIFERATIONOF PREFOLLICULARCELLSTHATEXTENDPROCESSESBETWEENCON TIGUOUS MEIOTIC OOCYTES4HIS RESULTS IN THE ISOLATION OFTHEGERMCELLSFROMOTHERCELLS THEREBYFORMINGA &/,,)#,%CONSISTINGOFANOOCYTESURROUNDEDBYAFOL LICULAR EPITHELIUM ENCLOSED BY ITS OWN BASAL LAMINA &IGURE ! 0REFOLLICULAR AND FOLLICULAR CELLS CON TAINCYTOPLASMIClLAMENTSTHATDISTINGUISHTHEMFROM EARLY MEIOTIC OOCYTES WHICH CONTAIN NO lLAMENTS .EWLYFORMEDFOLLICLESARESURROUNDEDBYATHIN4(%#! OFCONNECTIVETISSUEELEMENTS //'/.)! OF THE PIPEFISH THE STEM CELLS OF THE GERMCELLLINEAGEAREOVALTOSPHERICALCELLS ABOUT MINDIAMETER WHICHOCCURINTHELUMINALEPITHE LIUM NEARTHEGERMINALRIDGE ANDWITHINTHEGERMINAL RIDGEITSELF"EGOVACAND7ALLACE &IGURE 4HEYARECONTIGUOUSWITHOTHERGERMCELLSANDSOMATIC CELLS BUT ARE NOT IN CONTACT WITH THE BASAL LAMINA OF THELUMINALEPITHELIUM4HEYARETHEONLYGERMCELLS WITHIN THE GERMINAL RIDGE THAT INCORPORATE ;(= THY MIDINE INDICATING THAT THEY ARE THE ONLY GERM CELLS CAPABLE OF NUCLEAR DIVISION SOMATIC CELLS INCLUDING FOLLICULARCELLSANDCONNECTIVETISSUECELLSINCORPORATE THELABELASWELL/OGONIAHAVETHELARGESTNUCLEARCY TOPLASMICRATIOOFANYCELLSOFTHEGERMCELLLINE4HE OVALNUCLEICONTAINONETOTHREENUCLEOLI$ENSE CORED GRANULESOFUNKNOWNCOMPOSITIONWITHINTHENUCLEUS ARE SPECIlC TO NUCLEI OF THE GERM CELL LINE AND ARE ALSOPRESENTINLARGEROOCYTES/OGONIALCHROMATINIS MOREELECTRON DENSETHANTHATOFMEIOTICOOCYTES/O GONIAL CYTOPLASM CONTAINS MITOCHONDRIA RIBOSOMES ANDSCANTENDOPLASMICRETICULUMBUTAPPEARSTOLACKA 'OLGICOMPLEX!GGREGATESOF.5!'%MATERIALAREFRE QUENTLYASSOCIATEDWITHMITOCHONDRIATHISISANELEC TRON DENSE MEMBRANELESS ORGANELLE CONSISTING OF A SPONGELIKEAGGREGATIONOFlNEGRANULARMATERIAL4HE FUNCTIONANDCOMPOSITIONOFNUAGEAREUNCERTAINBUT ITSPRESENCEISARELIABLEMARKEROFGERMCELLS/OGO NIAOFTHESEALAMPREY0ETROMYZONMARINUSAPPEARTO

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4HEPROCESSOFTRANSFORMATIONOFOOGONIATOOOCYTES IS //'%.%3)33ELMANAND7ALLACE )TISGENER ALLYACCEPTEDTHATTHECHROMOSOMESBECOMEARRESTED ATDIPLOTENEOFTHElRSTMEIOTICPROPHASEANDTHEINITIAL FOLLICLEISESTABLISHED7ALLACEAND3ELMAN )T ISUNCLEARHOWOOGONIALDAUGHTERCELLSARETRANSFORMED INTOPROPHASE)MEIOTICOOCYTESANDWHETHERTHEOOGO NIALDIVISIONTHATPRODUCESTHEOOCYTESISSYMMETRICAL "EGOVACAND7ALLACE !LTHOUGHITISDIFlCULT TO DISTINGUISH THE EARLIEST MEIOTIC OOCYTES FROM OO GONIA SOME FEATURES ARE SAID TO CHARACTERIZE NEWLY FORMEDOOCYTESINTHESEQUENTIALLYARRANGEDOVARIESOF SYNGNATHIDSANINCREASEINSIZEALONGWITHADECREASE IN NUCLEARCYTOPLASMIC RATIO LOSS OF THE PERINUCLEAR RINGOFMITOCHONDRIAPROLIFERATIONOFOTHERORGANELLES ESPECIALLY 'OLGI COMPLEXES AND CHANGES IN NUCLEAR MORPHOLOGY ESPECIALLY CONDENSATION OF CHROMATIN "EGOVAC AND 7ALLACE 3ELMAN 7ALLACE AND 0LAYER &IGURES"AND! 4HEMOSTOBVI OUSSIGNOFTRANSFORMATIONOFOOGONIATOOOCYTESINTHE SEALAMPREYISTHEINCREASEINTHESIZEOFTHENUCLEUS ANDTHEAPPEARANCEOFAPROMINENTNUCLEOLUS,EWIS AND-C-ILLAN #YTOPLASMICBRIDGESHAVEBEENDESCRIBEDBETWEEN OOGONIA AND OOCYTES OF SOME TELEOSTS &IGURE "RUSLÏAND"RUSLÏ 'RANDIAND#OLOMBO THESEBRIDGESWERENOLONGEROBSERVEDWHENFOLLICULAR CELLSHADENVELOPEDTHEOOCYTE"RUSLÏ /NTHE OTHERHAND INTERCELLULARBRIDGESWERENEVEROBSERVED BETWEENOOGONIAOROOCYTESOFTHESYNGNATHIDS"EGO VACAND7ALLACE 3ELMAN 7ALLACE AND0LAYER !N INCREASE IN SIZE IS THE MOST OBVIOUS MANIFES TATION OF OOCYTE DEVELOPMENT &IGURE 4HE OO CYTE GROWS BOTH BY AN ENLARGEMENT OF THE NUCLEUS ANDTHEADDITIONOFCYTOPLASM,ATER MOSTGROWTHIS DUE TO AN INCREASE IN THE AMOUNT OF CYTOPLASM AND IN THE lNAL STAGES OF MATURATION THE OOCYTE HAS ITS FULLCOMPLEMENTOFYOLKANDISREADYTOBEOVULATED &OURPRINCIPALSTAGESOFOOCYTEDEVELOPMENT ASOUT LINED BELOW HAVE BEEN DESCRIBED IN SEVERAL TELEOSTS 7ALLACEAND3ELMAN 4HEMAJORCELLULARAND PHYSIOLOGICALPROCESSESOCCURRINGATEACHSTAGEOFTHE ZEBRAlSH "RACHYDANIO RERIO ARE OUTLINED BY 3ELMAN ETAL !VERAGEDIAMETERSOFFOLLICLESOOCYTES

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7ALLACE AND 3ELMAN -AYER 3HACKLEY AND2YLAND 3ELMANAND7ALLACE 3ELMAN ETAL 4HElRSTTYPEOFYOLKYINCLUSIONTOAC CUMULATEINMOSTSPECIESISLIPIDYOLKINTHEFORMOF DISTINCTLIPIDDROPLETSINTHEBASSTHESEMAKETHEIRAP PEARANCEINTHEOUTERCORTEXBUTINMOSTTELEOSTSTHEY lRST APPEAR IN THE PERINUCLEAR CYTOPLASM GIVING RISE TOSUGGESTIONSTHATTHEYAREPROBABLYFORMEDENDOG ENOUSLY &IGURE 0ROTEIN YOLK ACCUMULATION IS EXOGENOUS IN ORIGIN AND OCCURS AFTER AND CONCOMI TANTTO LIPIDYOLKACCUMULATION)NMOSTTELEOSTS YOLK PROTEINS ACCUMULATE IN mUID lLLED YOLK SPHERES THAT MAYEITHERMAINTAINTHEIRINTEGRITYTHROUGHOUTOOCYTE GROWTHORFUSECENTRIPETALLY EVENTUALLYFORMINGACON TINUOUS MASS OF mUID YOLK A PROCESS WHICH CONFERS ONMANYTELEOSTEGGSTHEIRCHARACTERISTICTRANSPARENCY &IGURE 4HIS COALESCENCE CAN OCCUR RELATIVELY SOONAFTERTHEINITIALFORMATIONOFYOLKSPHERES ASIN STICKLEBACKSANDTHEPIPElSH DURINGTHELATERSTAGESOF VITELLOGENESIS ASINTHESHEEPSHEADMINNOW ORDURING MATURATION AS IN THOSE MARINE TELEOSTS THAT PRODUCE PELAGICEGGS#REATIONOFACENTRALMASSOFmUIDYOLK DISPLACES THE OOPLASM WITH ITS CORTICAL ALVEOLI AND LIPIDDROPLETS TOTHEPERIPHERYOFTHEOOCYTE&IGURE !FEWYOLKSPHERESALWAYSREMAININTHEPERIPH ERALOOPLASM BUTAPPEARTOBEREDUCEDINNUMBERAS THECENTRALMASSINCREASES&IGURE 3HACKLEYAND +ING )NSOMESPECIES PROTEINYOLKISSEQUESTEREDINTHE FORMOFDISCRETEGRANULESTHATSTAININTENSELYFORPRO TEINSBUTNOTFORLIPIDSORCARBOHYDRATES&IGURE 3ELMANAND7ALLACE 3ELMANETAL 4HE SURFACEOFTHEOOCYTEDISPLAYSCONSIDERABLEENDOCYTO TICACTIVITYDURINGTHISSTAGEANDELECTRON DENSEMATE RIALISVISIBLEINSOMEENDOCYTOTICSTRUCTURES4HEYOLK PLATELETSOFTHEZEBRAlSH"RACHYDANIORERIOAREVARI ABLEINSIZEANDSOMEMAYATTAINDIAMETERSOFM 4HECONTENTSOFMOSTOFTHESEYOLKBODIESARENOTHO MOGENEOUSANDGENERALLYDISPLAYONETOSEVERALRECTI LINEARMASSESEMBEDDEDINAHOMOGENEOUSMATRIX)N APPROPRIATELYORIENTEDSECTIONS THESEMASSESDISPLAY AN ORTHORHOMBIC CRYSTALLINE STRUCTURE WITH PARALLEL DENSEBANDSAPPROXIMATELYNMAPART&IGURE 4HISGRANULARYOLKBECOMESTHEPREDOMINANTYOLKIN CLUSION AND DENSELY PACKS THE MID AND OUTER CORTEX 5NLIKE THE mUID YOLK DROPLETS THAT COALESCE AS THEY MIGRATE CENTRIPETALLY PROTEIN YOLK GRANULES MAINTAIN THEIRSTRUCTURALINTEGRITYUNTILMATURATION AFTERWHICH THEYACTIVELYCOALESCE

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9/,+ '2!.5,%3ARECHARACTERISTICOFFRESHWATERTE LEOSTS ,ANGE ET AL ALTHOUGH THEY HAVE BEEN NOTEDINEGGSOFTHECOD'ADUSMORHUA+JESBUAND +RYVI !SDESCRIBEDINAWIDERANGEOFlSHES THEY CONSIST OF ONE OR MORE CRYSTALLINE MAIN BODIES WITHIN AN AMORPHOUS SUPERlCIAL LAYER ENCLOSED BY A MEMBRANE&IGURE 9AMAMOTOAND/OTA 7ALLACE %LEGANTCRYSTALSHAVEBEENDESCRIBED WITHIN THE MAIN BODY OF YOLK PLATELETS FROM A WIDE VARIETYOFlSHESCYCLOSTOMES+ARASAKI 5LRICH 0ATZNER ,ANGEAND2ICHTER ,ANGE TELEOSTS ,ANGE ET AL AND THE ANCIENT lSHES0OLYPTERUSBICHIR !MIACALVA AND,EPISOSTEUS OSSEUS ,ANGE 'RODZINSKI AND +ILARSKI 4HE CRYSTALSOFCYCLOSTOMESAPPEARTOBEAMONOCLINICLAT TICE OF POSSIBLY SYMMETRIC LIPOVITELLIN PHOSVITIN DI MERSWHEREASTHOSEOFTELEOSTSANDTHEANCIENTlSHES ARE AN ORTHORHOMBIC ARRAY OF LIPOVITELLIN PHOSVITIN COMPLEXES CONSISTING OF TWO SUBUNITS THAT ARE LIKELY NOTIDENTICAL4HISCRYSTALLINESTRUCTUREISRAREINMA RINESPECIES SUGGESTINGTHATTHECRYSTALSMAYSTOREES SENTIALNUTRIENTS UNAVAILABLEINFRESHWATER PROVIDING REGULARLY PACKED MICROCHAMBERS THAT SEQUESTER LOW MOLECULARWEIGHTPARTICLESORIONS,ANGE 'RODZINS KI AND+ILARSKI 8 RAYANALYSISOFCRYOSECTIONS INDICATESTHEPRESENCEOFCHLORIDEANDAVARIETYOFCAT IONSWITHINTHEPLATELETS,ANGE ,ANGEET AL %ARLY VITELLOGENESIS IN THE PIPElSH IS CHARACTER IZED BY THE APPEARANCE OF INDIVIDUAL SMALL MEM BRANE BOUNDYOLKSPHERESINTHEOOCYTEPERIPHERYAND INTERIOR&IGURES!TO# "EGOVACAND7ALLACE !SVITELLOGENESISPROGRESSES THEYOLKSPHERES INCREASEINSIZEWHILETHECORTICALALVEOLIANDLIPIDARE DISPLACED TO THE PERIPHERAL OOPLASM %VENTUALLY THE YOLKSPHERESCOALESCETOFORMACENTRALmUIDMASSTHE CORTICALALVEOLIANDLIPIDREMAININTHEPERIPHERALPART OFTHEYOLKMASS9OLKSPHERESAREMODERATELYELECTRON DENSE AND CONTAIN HIGHLY ELECTRON DENSE INCLUSIONS THATOCCASIONALLYHAVEAlNELYGRANULARAPPEARANCEAND PROVIDEASPECIlC RELIABLEMARKERFORFOLLOWINGYOLK FORMATION&IGURES$ % 4HEREARETHREETYPESOF SMALLYOLKSPHERESPRIMARY TRANSITIONAL ANDMATURE 02)-!299/,+30(%2%3APPEARTOCONTAINPROTEINACEOUS MATERIALINTERSPERSEDAMONGMULTIVESICULARELEMENTS ).4%2-%$)!4% 42!.3)%.49/,+30(%2%3CONTAINPROTEIN ACEOUSMATERIAL VARIABLEVESICULARELEMENTS ANDTHE YOLK SPECIlC ELECTRON DENSEINCLUSION-!452% 9/,+ 30(%2%3CONTAINHOMOGENEOUS CONDENSEDYOLKANDA HETEROGENEOUS SIZE AND DISTRIBUTION OF THE YOLK SPE

CIlC MARKER &IGURES $ & )T IS SUGGESTED THAT THE MULTIVESICULAR BODIES REPRESENT A MODIlED LYSO SOMALCOMPARTMENTINVOLVEDINYOLKSPHEREFORMATION "EGOVAC AND 7ALLACE 3ECONDARY LYSOSOMES ORMULTIVESICULARBODIESARESEENADJACENTTOCORTICAL ALVEOLIINOOCYTESOFTHESEAHORSEANDPIPElSHATABOUT THE TIME OF THE ONSET OF VITELLOGENESIS &IGURE AND MAY BE REQUIRED FOR THE PROTEOLYTIC PROCESSING INTOMATUREYOLKPROTEINSOFTHEVITELLOGENINTAKENUP BYENDOCYTOSIS&IGURE' 3ELMAN 7ALLACE AND 0LAYER -ULTIVESICULAR BODIES SEEM TO DISAP PEARASVITELLOGENESISPROGRESSES 4HE INVOLVEMENT OF LYSOSOMES OR MULTIVESICULAR BODIESINVITELLOGENESISHASBEENDEMONSTRATEDINOO CYTESOFTHETROUT3ALMOTRUTTAFARIO"USSON -ABILLOT !T AN EARLY STAGE OF DEVELOPMENT LYSOSOMES ARISEINTHECORTICALOOPLASMANDMIGRATECENTRIPETALLY ALMOST REACHING THE NUCLEUS EVENTUALLY THEY CONSTI TUTETHEMOSTVOLUMINOUSCOMPARTMENTOFTHEOOCYTE &IGURE 4HEYAREMEMBRANE BOUNDANDCONTAIN SMALLVESICLESANDCLUMPSOFlNELYGRANULARMATERIAL &IGURE! #ONTINUITIESAREABUNDANTBETWEENTHE AGRANULAR ENDOPLASMIC RETICULUM AND THE MEMBRANE ENCLOSINGTHELYSOSOMES&IGURE" !TTHEBEGIN NINGOFVITELLOGENESIS ENDOCYTOTICVESICLESCONTAINING VITELLOGENINFUSEWITHONEANOTHERTOFORMLARGERVES ICLESANDTHESETHENFUSEWITHLYSOSOMESTOFORMYOLK BODIESTHATMAYATTAINDIAMETERSUPTOM&IGURE 'RANULARMATERIALGRADUALLYlLLSTHELYSOSOMES ATTHEONSETOFVITELLOGENESISAND OVERSEVERALWEEKS THISTRANSFORMSINTOHOMOGENEOUSYOLK&IGURE /THERCHANGESAREAPPARENTWITHINTHEFOLLICLEDUR INGVITELLOGENESIS3ELMANAND7ALLACE "EGO VACAND7ALLACE +JESBU +RYVI AND.ORBERG 4HEGERMINALVESICLEISPROGRESSIVELYDISPLACED TOWARD THE ANIMAL POLE AS YOLK ACCUMULATES CENTRIP ETALLY WITHIN THE OOCYTE 3OME SMALL LIPID DROPLETS REMAIN ASSOCIATED WITH THE GERMINAL VESICLE WHILE OTHERS BEGIN TO FUSE REACHING DIAMETERS OF TO M ANDRESIDEINTHEPERIPHERALOOPLASM)N&UNDULUS THEZONAPELLUCIDACONTINUESTOENLARGE ACQUIRINGAN ELABORATESTRUCTUREWHEREAS IN3YNGNATHUS ITUNDER GOESCONDENSATION4HEREISACLOSESTRUCTURALRELATION SHIPBETWEENBUNDLESOFMICROlLAMENTSANDANNULATE LAMELLAEINVITELLOGENICOOCYTES+ESSEL "EAMS AND 4UNG )TISSUGGESTEDTHATTHEREISACOPARTICIPA TION OF PORES OF THE ANNULATE LAMELLAE AND POLYRIBO SOMESINTHEDEVELOPMENTOFMICROlLAMENTBUNDLES 6ITELLOGENESIS IN THE ELASMOBRANCH 3CYLIORHINUS CANICULADOESNOTAPPEARTODIFFERFUNDAMENTALLYFROM

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OTHER VERTEBRATES EITHER IN THE MECHANISM OF VITELLO GENESISORINITSIMMEDIATEENDOCRINECONTROL#RAIK A B C D E 6ITELLOGENIN IS PRESENT IN THE PLASMA THROUGHOUTTHEYEARANDITSUPTAKEBYGROWINGOVARIAN FOLLICLESSEEMSTOBESTIMULATEDBYAHORMONEFROMTHE CRANIALPARSDISTALISOFTHEPITUITARY !N UNUSUAL FORM OF YOLK UPTAKE IS DESCRIBED IN THELAMPREY0ETROMYZONMARINUSWHEREBOTHTHEOO CYTE AND CERTAIN ENLARGED FOLLICULAR CELLS THE hNURSE CELLSv SIMULTANEOUSLYFORMYOLKPLATELETS,EWISAND -C-ILLAN 4HESECELLSEVENTUALLYFUSEANDTHE YOLK RICH CYTOPLASM FROM THE NURSE CELLS IS INCORPO RATED INTO THE OOCYTE 4HE NUCLEUS OF THE NURSE CELL DISAPPEARS

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THROUGHOUT THE ANNUAL CYCLE )N ADDITION THESE CELLS CONTAINFREERIBOSOMES GRANULARENDOPLASMICRETICU LUM POLYRIBOSOMES 'OLGICISTERNAE AFEWLYSOSOME LIKE BODIES AND LIPID DROPLETS (ISTOCHEMICAL TESTS INDICATE THAT THE INTERSTITIAL CELLS AND SPECIAL THECAL CELLSARETHESITESOFMOSTINTENSESTEROIDOGENESIS ES PECIALLYDURINGTHEPERIODWHENMATURATIONOFOOCYTES AND OVULATION TAKES PLACE!T THIS TIME THE NUMBERS OF THESE STEROIDOGENIC CELLS INCREASE 4HE LOCALIZA TIONANDNATUREOFTHESPECIALTHECALCELLSINTHETROUT OVARYINDICATETHATTHEYAREINTERSTITIALCELLS FOUNDIN THE OUTER PART OF THE THECA OF PRE AND POSTOVULATORY FOLLICLES "UNDLES OF NERVE lBRES PRESUMABLY AUTONOMIC COURSE AMONG THE YOLKY FOLLICLES AND STEROID PRO DUCINGCELLSOFTILAPIA/REOCHROMISNILOTICUS&IGURE % .AKAMURA 3PECKER AND.AGAHAMA 4HICK NERVE BUNDLES ENTER THE OVARY IN ASSOCIATION WITHTHEOVARIANARTERYANDVEIN&IGURES!TO# ANDSENDOUTBRANCHESTHATINVADETHECENTRALPARTSOF THEOVIGEROUSLAMELLAE'ROUPSOFAXONSRAMIFYFROM THESEBUNDLESTOPENETRATETHESPACESBETWEENCLUSTERS

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/65,!4)/.

)NTRODUCTION

#ARASSIUS AURATUS +AGAWA AND .AGAHAMA HYDROCORTISONE /RYZIAS LATIPES 0ENDERGRASS AND3CHROEDER ORTHEMATURATION INDUCINGSTE ROIDS ` TRIHYDROXY PREGNENE ONE` 3 AND ` DIHYDROXY PREGNENE ONE ` 0 #YNOSCION NEBULOSUS 0INTER AND 4HOMAS TO THEMEDIUM 3OME TIME PRIOR TO OVULATION IN &UNDULUS HETERO CLITUS EACH FOLLICLE ESTABLISHES A CLOSE RELATIONSHIP WITH THE LUMINAL SURFACE OF THE OVARY IN A LOCALIZED NEARLYCIRCULARSPOT"RUMMETT $UMONT AND,ARKIN ! FUSION BETWEEN THE BASEMENT MEMBRANES OF THE FOLLICULAR CELLS AND LUMINAL EPITHELIUM AP PEARSTOOCCUR EXCLUDINGBLOODVESSELSFROMTHEAREA &IGURE 4HESQUAMOUSLUMINALMESOTHELIALCELLS COVERING THIS AREA BECOME INCREASINGLY mAT AS THE FOLLICLE MATURES AND IT IS PRESUMED THAT OVULATION OCCURS AT THIS SITE4HIS AVASCULARAREA IS SURROUNDED BYARAISEDLIPOFCELLSCONTAININGARING SHAPEDVES SELTHATCOLLECTSBLOODFROMCAPILLARIESINTHEFOLLICULAR THECA &IGURES ! # 4HE MATURE EGG OF &UNDU LUSISOVULATEDINTOTHELUMENOFTHEOVARYANDPASSES FROM THERE TO THE POSTERIOR NONGERMINAL PORTION OF THEOVARY THE/6)3!# 5LTRASTRUCTURALSTUDIESHAVEREVEALEDTHATMICROVILLI FROM BOTH FOLLICULAR CELLS AND THE OOCYTE WITHDRAW FROMTHEZONAPELLUCIDANEARTHETIMEOFOVULATIONAND THAT A WIDE SPACE FORMS BETWEEN THE ZONA PELLUCIDA ANDTHEFOLLICULARCELLS&IGURE &LàGEL B (IROSE )WAMATSUAND/HTA 4HEMECHA NISMDIRECTINGTHISINTERRUPTIONOFFOLLICLE OOCYTECOM MUNICATIONPRIORTOOVULATIONISUNKNOWN 4HEPRESENCEOFhOVULATION INDUCINGENZYMESvHAS BEENPOSTULATEDFORSEVERALlSH4HESEARETHOUGHTTO BREAKDOWNCOLLAGEN THEREBYWEAKENINGTHEFOLLICULAR WALLINPREPARATIONFORITSRUPTURE)SOLATEDFOLLICLESOF

!FTERCOMPLETIONOFTHElRSTMEIOTICDIVISION ARUP TURETHE34)'-! DEVELOPSINASPECIlCAREAOFTHEFOL LICULARWALLANDTHEMATUREOOCYTESARERELEASEDINTO THECOELOMOROVARIANCAVITYBYTHEPROCESSOFOVULA TION .AGAHAMA -EIOSIS CONTINUES UP TO THE SECONDMEIOTICMETAPHASEAND ATTHISTIME THEEGGS AREREADYFORFERTILIZATION3EVERALSTEPSAREINVOLVED INTHISRELEASESEPARATIONOFTHEVITELLINEENVELOPEAND FOLLICULAREPITHELIUMASMICROVILLIFROMBOTHSIDESBE COMEDETACHEDENZYMATICDEGRADATIONANDRUPTUREOF THEFOLLICLEANDEXPULSIONOFTHEOOCYTE4HEMOTIVE FORCE EXPELLING THE OOCYTE HAS BEEN ATTRIBUTED VARI OUSLYTOTHEFORMATIONOFmUIDSWITHINTHEFOLLICLE TO SWELLINGOFTHEOOCYTE ANDTOCONTRACTIONSOFTHEFOL LICULARWALL)NSOMEVIVIPAROUSSPECIES FERTILIZATION ANDEMBRYOLOGICALDEVELOPMENTTAKEPLACEWITHINTHE FOLLICLE SO THAT NO OVULATION OCCURS 3UBSEQUENT RE LEASEOFTHEEMBRYOSFROMTHEIRFOLLICULARSANCTUARYIS SOMETIMESREFERREDTOAShOVULATIONvEG 6ENKATESH 4AN AND,AM A B BUTTHISUSAGESEEMSINAPPRO PRIATEANDWILLNOTBEUSEDINTHISTEXT 6ARIOUSASPECTSOFOVULATIONHAVEBEENSTUDIEDDUR INGITSNORMALOCCURRENCEINTHEREPRODUCTIVECYCLEOF INTACTlSH#ARASSIUSAURATUS.AGAHAMA #HAN AND (OAR 0ETROMYZONMARINUS9ORKEAND-C-IL LAN 3ALVELINUSLEUCOMAENIS+AGAWA 4AKANO AND.AGAHAMA (OWEVER SINCETHISEVENTOC CURS OVER A BRIEF PERIOD OF TIME IT HAS OFTEN PROVED CONVENIENT TO INDUCE OVULATION IN FEMALES BY MA NIPULATIONS OF DAY LENGTH /RYZIAS LATIPES (IROSE +AGAWAAND4AKANO )WAMATSUAND/HTA A OR BY INJECTIONS OF HORMONES SUCH AS HUMAN CHORIONIC GONADOTROPIN (#' 0LECOGLOSSUS ALTIVE LIS (IROSE AND )SHIDA ,IMANDA YOKOHOMAE /SHIRO AND (IBIYA )N FOLLICLES ISOLATED FROM GRAVIDFEMALES OVULATIONHASBEENINDUCEDBYADDI TIONSOFPROSTAGLANDIN&_3ALMOGAIRDNERI*ALABERT AND 3ZÚLLÚSI 3ZÚLLÚSI *ALABERT AND "RETON

0ETERAND9U HAVEPRESENTEDANEXTENSIVEREVIEWSUMMA RIZINGTHEMAJORENVIRONMENTALANDHORMONALFACTORSCONTROLLING OVULATIONINTELEOSTS

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THE LOACH -ISGURNUS ANGUILLICAUDATUS PRODUCE PRO TEASES IMMEDIATELY BEFORE INDUCED OVULATION /S HIROAND(IBIYA 3EVERALLYTICENZYMES CHYMOTRYPSIN AMINOPEPTIDASES ACID AND ALKALINE PHOSPHATASES VARIOUS ESTERASES AND GLYCOSIDASES WERE FOUND IN THE COELOMIC mUID OF THE TROUT 3ALMO GAIRDNERI WITHIN HR OF OVULATION BUT NO COLLAGE NASECOULDBEDETECTED3ZÚLLÚSI *ALABERT AND"RETON )N ADDITION COLLAGENASE WAS SOUGHT WITHOUT SUCCESSINEXTRACTSOFPRE ANDPOSTOVULATORYOVARIES !CTINOMYCIN $ AND CYCLOHEXAMIDE INDUCED BLOCK AGE OF STEROID INDUCED OVULATION IN ISOLATED FOLLICLES OFYELLOWPERCH0ERCAmAVESCENS PRESUMABLYBYIN HIBITINGPRODUCTIONOFTHEPROTEOLYTICENZYMESNEEDED TODETACHTHEOOCYTEFROMTHEFOLLICLEANDWEAKENTHE FOLLICULAR WALL 4HEOFAN AND 'OETZ -ORE RE CENTLY COLLAGENOLYTIC METALLO PROTEASES HAVE BEEN DEMONSTRATEDINFOLLICULARWALLSOFYELLOWPERCHAND BROOK TROUT 3ALVELINUS FONTINALIS AROUND THE TIME OF OVULATION"ERNDTSONAND'OETZ )NCREAS ESINTHENUMBERSOFLYSOSOMESWITHINFOLLICULARCELLS NEARTHETIMEOFOVULATIONHAVEPROVIDEDMORPHOLOGI CALEVIDENCEFORTHEPRESENCEOFHYDROLYTICENZYMESIN THESECELLS9AMAMOTOAND9AMAZAKI +AGAWA AND4AKANO +AGAWA 4AKANO AND.AGAHAMA !NINCREASEINLYSOSOME LIKEBODIESWASALSO OBSERVEDINFOLLICULARCELLSOFCULTUREDFOLLICLESOFTHE MEDAKA JUST BEFORE OVULATION WAS EXPECTED TO OCCUR &IGURE )WAMATSUAND/HTA A )T HAS BEEN SUGGESTED THAT THE ACCUMULATION OF mUID WITHIN THE FOLLICLE COULD APPLY GENTLE PRESSURE TOEXPELTHEOOCYTEASWELLASLUBRICATINGITSPASSAGE !S THE TIME OF OVULATION APPROACHES IN THE LAMPREY 0ETROMYZONMARINUS THEREISANACCUMULATIONOF&,5)$ /& /65,!4)/. BETWEEN THE VITELLINE ENVELOPE AND THE FOLLICULAREPITHELIUMINTHEAPICALREGIONSOFTHEFOL LICLE&IGURE ,EWISAND-C-ILLAN 9ORKE AND-C-ILLAN !CIDANDNEUTRALMUCOPLYSAC CHARIDES PRESENT IN THE FOLLICULAR CELLS THAT DISTINT EGRATE AT OVULATION MAY PARTICIPATE IN THIS PROCESS ANDITISSUGGESTEDTHATENZYMATICBREAKDOWNOFACID MUCOPOLYSACCHARIDES MAY CAUSE THE OSMOTIC UPTAKE OF WATER CAUSING SWELLING OF THE NEUTRAL MUCOPOLY SACCHARIDES,ARSEN 4HEREWASAGREATINmUX OF WATER INTO OVARIES OF AYU 0LECOGLOSSUS ALTIVELIS AND PLAICE ,IMANDA YOKOHOMAE JUST PRIOR TO OVU LATION THAT WAS INDUCED BY INJECTIONS OF HORMONES (IROSEAND)SHIDA /SHIROAND(IBIYA -OSTOFTHEWATERWASABSORBEDBYFULLY GROWNYOLKY OOCYTESTHATOVULATEDSOONAFTERANDITWASSUGGESTED

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SIVECELLSANDBORDERINGDIRECTLYONTHECOELOM&IGURE ! 4HUSFREED THEEGGEMERGESINTOTHECOELOM #ONTRACTIONSOFTHETHECAASSISTOVULATIONINSEVERAL TELEOSTS4HETHECABEHAVESPHYSIOLOGICALLYLIKESMOOTH MUSCLEWHOSECONTRACTIONSCANBEEVOKEDINVITROBY THE ADDITION OF PROSTAGLANDIN &_ 3ZÚLLÚSI *ALABERT AND"RETON 4HECALCELLSOFSEVERALSPECIESRE SEMBLESMOOTHMUSCLECELLS DISPLAYINGABUNDANTMI CROlLAMENTSTONM ANDPINOCYTOTICVESICLESPRIOR TOOVULATION&IGURES! " 3ZÚLLÚSIAND*ALABERT 0ENDERGRASS AND 3CHROEDER .AGAHAMA #HAN AND(OAR 3ZÚLLÚSI *ALABERT AND"RETON )NSOMESPECIES HOWEVER THEDENSEBODIESAND PINOCYTOTIC VESICLES CHARACTERISTIC OF SMOOTH MUSCLE HAVE NOT BEEN SEEN 0HYSIOLOGICAL EVIDENCE FOR CON TRACTILITYOFTHEMICROlLAMENTSOFTHETHECALCELLSHAS BEENPROVIDEDCYTOCHALASIN" WHICHBLOCKSPOLYM ERIZATIONOFACTINlLAMENTS THEREBYPARALYSINGMANY KINDSOFCELLULARMOVEMENT COMPLETELYANDREVERSIBLY INHIBITSINVITROOVULATIONOFMEDAKAANDTROUTOOCYTES *ALABERT AND 3ZÚLLÚSI 3CHROEDER AND 0ENDER GRASS AND AGENTS THAT BLOCK #A INmUX NE CESSARYFORMUSCULARCONTRACTION INHIBITOVULATIONOF TROUTOOCYTESINVITRO*ALABERTAND3ZÚLLÚSI 4HE 02/34!',!.$).3AREAGROUPOF CARBONFATTY ACIDSCONTAININGA CARBONRINGTHEYARESHORT LIVED ANDAFFECTAWIDEVARIETYOFPHYSIOLOGICALPROCESSESBY ACTINGASLOCALHORMONES4HEYAPPEARTOPLAYASIGNIF ICANTROLEINOVULATIONINOVIPAROUSTELEOSTSALTHOUGH THEEFFECTIVEPROSTAGLANDINSVARYFROMSPECIESTOSPE CIES*ALABERT 'OETZAND4HEOFAN 'OETZ ET AL "ERNDTSON 'OETZ AND $UMAN 'OETZ ET AL A B )N OVIPAROUS TELEOSTS WHERE OVULATION IMMEDIATELY FOLLOWS OOCYTE MATURATION FOLLICLES SYNTHESIZE LARGE AMOUNTS OF PROSTAGLANDINS DURING OOCYTE MATURATION AND OVULATION "ERNDTSON AND 'OETZ "ERNDTSON ET AL A 'OETZ ET AL B "YCONTRAST INTHEVIVIPAROUSGUPPY0OE CILIARETICULATA WHERETHEFOETUSDEVELOPSWITHINTHE FOLLICLEANDISRELEASEDACONSIDERABLETIMELATER PRO DUCTION OF PROSTAGLANDINS BY FOLLICLES IS LOW DURING OOCYTEGROWTH MATURATIONANDGESTATIONITINCREASES SIGNIlCANTLY IN MID AND LATE GESTATION4HIS DELAY IN SYNTHESIS MAY ARREST OVULATION THEREBY FACILITATING INTRAFOLLICULAR FERTILIZATION AND GESTATION 6ENKATESH 4AN AND ,AM B 3EVERAL TISSUE COMPONENTS WITHINTHEOVARYOFTHEBROOKTROUT3ALVELINUSFONTINA LISSYNTHESIZEPRIMARYPROSTAGLANDINSBUTDIFFERINTHEIR CAPACITYTOPRODUCE%AND&PROSTAGLANDINS'OETZET AL B !LTHOUGH FOLLICULAR WALLS SYNTHE

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INTHEINCIDENCEOFATRESIAINVITELLOGENICOOCYTESWITH DECREASED FEEDING LEVELS +JESBU ET AL -ASS ATRESIAOFMATURINGOOCYTESINWILDSTOCKSOF!TLANTIC CODHASBEENATTRIBUTEDTOSEVEREMALNUTRITIONDURING SOME CRITICAL PERIOD FOR OVARIAN GROWTH RESULTING IN AFAILURETOSPAWNORhSKIPPEDSPAWNINGvINMOSTFE MALESDURING2IDEOUT "URTON AND2OSE )TISSUGGESTEDTHATTHISFAILUREMAYHAVECONTRIBUTED TO THE CURRENT LACK OF RECRUITMENT IN NORTH !TLANTIC CODSTOCKS !LTHOUGHATRESIAMAYAFFECTTHEOOCYTEATANYSTAGE OFDEVELOPMENT ITISDESCRIBEDMOREFREQUENTLYINMA TURINGANDUNOVULATEDMATUREOOCYTES2ASTOGI 4HE APPARENT RARITY OF SMALL ATRETIC FOLLICLES MAY BE DUETOTWOFACTORSSMALLFOLLICLESTAKEASHORTERTIME THANMATUREFOLLICLESTODISAPPEARAND BEINGSMALLER APPEARINFEWERMICROSCOPICSECTIONS!TRESIAOFSMALL FOLLICLES IS DESCRIBED IN SEVERAL SPECIES OF ELASMO BRANCHS (ISAW AND (ISAW /VA CONTAINING NO YOLK APPARENTLY UNDERGO SIMPLE ABSORPTION 4HE CLEAR mUID CONTENT OF THE OVUM DECREASES THE WALLS OF THE FOLLICLE COLLAPSE AND THE FOLLICULAR LAYER ATRO PHIESANDDISINTEGRATES)NSLIGHTLYLARGERFOLLICLES IN WHICH SMALL AMOUNTS OF YOLK HAVE BEEN DEPOSITED SECRETIONOFYOLKCEASESANDTHEFOLLICULAREPITHELIUM INCREASES IN THICKNESS BY ELONGATION AND SWELLING OF CELLS WHICH MAY REMAIN ATTACHED TO THEIR BASEMENT MEMBRANE&OLLICULARCELLSlLLWITHVACUOLESANDTHE VITELLINEENVELOPEDISAPPEARS9OLKGRANULES LIBERATED BYDISINTEGRATIONOFTHEOVUM ASWELLASDÏBRISFROM THEDEGENERATINGOVUM AREREMOVEDBYFOLLICULARCELLS WHICHBECOMEPHAGOCYTIC 4HElRSTSIGNOFATRESIAINSMALL YOLK FREEOOCYTES OFTHEFRESHWATERMUDEEL !MPHIPNOUSCUCHIA ISTHE DISAPPEARANCE OF THE NUCLEAR MEMBRANE AND DISINTE GRATION OF CHROMATIN 2ASTOGI 4HE OOLEMMA IS THROWN INTO FOLDS INVADING THE DECOMPOSED OO PLASM 4HE FOLLICULAR EPITHELIUM REMAINS SINGLE LAY ERED AND SHOWS NO HYPERPLASIA 4HE THECA THICKENS ANDBECOMESMOREVASCULAR&OLLICULARCELLSINVADETHE OOCYTE FUNCTIONINGASPHAGOCYTESTHISINVASIONISFOL LOWEDBYTHATOFVASCULARTHECALTISSUE%VENTUALLYTHE OOLEMMAANDOOPLASMAREREMOVED4HEPHAGOCYTES BECOME PYCNOTIC AND ARE SUSPENDED IN A MESHWORK OFlBROUSTHECALMATERIAL4HISMASSSHOWSNOSIGNOF SECRETORYACTIVITY )NFOLLICULARATRESIAOFYOLKYFOLLICLES THESEQUENCE OF EVENTS IS SIMILAR IN MOST lSH #9#,/3/-%3 ,EWIS AND-C-ILLAN %,!3-/"2!.#(3(ISAWAND(I SAW #HIEFl ,ANCEAND#ALLARD 4E

7INKEL &ASANO 0IERANTONI AND#HIEFl #HIEFl "ACCARI ET AL 4%,%/343 "RETSCHNEIDER AND$UYVENÏDE7IT 2AI #HAN 7RIGHT AND0HILLIPS 0ANT 7IEBE 2ASTOGI 3HRIVASTAVA ,AMBERT B VAN DEN (URKAND0EUTE "ABUAND.AIR -IRANDA ETAL )NEARLYSTAGES THEFOLLICULARCELLSPROLIF ERATE AGGRESSIVELYFRAGMENTTHEVITELLINEENVELOPE AND INVADETHEOOCYTE REMOVINGITSCONTENTSBYPHAGOCYTO SIS&IGURE !STHEOOCYTEDISINTEGRATES THEREISA FOLDINGANDCOLLAPSEOFTHEFOLLICULARWALL&IGURE )NSEVERALSPECIESOFlSH THEFOLLICULARLAYEROFLARGER FOLLICLESBECOMESDEEPLYFOLDEDDURINGATRESIA GREATLY INCREASINGTHEABSORPTIVESURFACEEXPOSEDTOTHEYOLK &IGURE (ISAWAND(ISAW 2ASTOGI $ODDAND3UMPTER 4HEBASEMENTMEMBRANERE MAINSINTACTANDCONNECTIVETISSUEOFTHETUNICAINTIMA ISCARRIEDINTOTHEFOLDSALONGWITHBRANCHESOFBLOOD VESSELS5LTRASTRUCTURALOBSERVATIONSONTHEPHAGOCYTIC REMOVALOFTHEOOCYTEINTHEPERCH0ERCAmUVIATILISAND THEELECTRICRAY4ORPEDOMARMORATAINDICATEDISSOLU TIONOFTHEOOCYTENUCLEUS DISINTEGRATIONOFTHEYOLK MASS BREAKDOWNOFCORTICALALVEOLI ANDDEGENERATION OF MITOCHONDRIA AND OTHER CYTOPLASMIC CONSTITUENTS &IGURES!AND!TO$ ,ANG B#HIEFl "ACCARIETAL )NCREASINGNUMBERSOFSMALLCY TOPLASMICVACUOLESAPPEARINTHEFOLLICULARCELLSDURING THE EARLY STAGES OF ATRESIA AND GRANULAR ENDOPLASMIC RETICULUM INCREASES AT THE SAME TIME &IGURES " TO ' 3EVERAL 'OLGI COMPLEXES SHED SMALL VESICLES THAT COALESCE INTO SMOOTH SURFACED TUBULES 4HECAL CELLS AND LEUCOCYTES WHICH INVADE THE FOLLICLE FROM SURROUNDING CAPILLARIES APPEAR TO TAKE NO PART IN DI GESTING OR TRANSFORMING OOCYTIC MATERIAL !GRANULAR ENDOPLASMIC RETICULUM AS WELL AS MITOCHONDRIA WITH TUBULAR CRISTAE ARISE IN FOLLICULAR CELLS OF THE ELECTRIC RAY 4ORPEDO MARMORATA SUGGESTING A STEROIDOGENIC ROLEFORTHESECELLS&IGURES% & #HIEFl"ACCARI ETAL )NDEED THENUCLEIOFTHESECELLSMIGRATE FROMTHEBASALTOAPICALPOLESATTHISTIME INDICATING THECHANGEINTHEROLEOFTHESECELLSFROMPHAGOCYTOSIS OFYOLKTOTHERELEASEOFSECRETIONSINTOTHERICHLYVAS CULARIZEDSTROMA)NADDITION THEPRESENCEOF` (3$ ACTIVITYINTHEFOLLICULARCELLSIMPLIESSTEROIDOGENICAC TIVITY,UPO$I0RISCO CITEDBY#HIEFl"ACCARI ETAL /NTHEOTHERHAND TELEOSTSHAVEREVEALED NOEVIDENCEOFGLANDULARFUNCTIONINTHEPOSTOVULATORY CORPUSLUTEUM !S THE AMOUNT OF YOLK IN THE FOLLICLE DECREASES PHAGOCYTOSIS BY THE FOLLICULAR CELLS DECREASES AND

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ALLY BECOMES INDISTINGUISHABLE FROM THAT REMAINING FROMANATRETICFOLLICLE 0OSTOVULATORY FOLLICLES OF THE "RAZILIAN CHARACIN !STYANAX BIMACULATUS LACUSTRIS HAVE BEEN USED AS A MODEL FOR !0/04/3)3 OR GENETICALLY PROGRAMMED CELL DEATH A NORMAL PHYSIOLOGICAL PROCESS OF SELF DE STRUCTION $RUMMOND ET AL !POPTOSIS IS THE MAJOR MECHANISM RESPONSIBLE FOR THE ELIMINATION OF FOLLICULAR CELLS IN THE POSTOVULATORY FOLLICLES DURING OVARIAN RECOVERY AFTER SPAWNING 0OSTOVULATORY FOL LICLESARERAPIDLYREABSORBEDASTHEFOLLICULARCELLSDE VELOPPHAGOCYTICACTIVITY4HEFOLLICULARCELLSUNDERGO HYPERTROPHYAFEWHOURSAFTERSPAWNING SHOWINGTHE WELL DEVELOPED ORGANELLES CHARACTERISTIC OF PROTEIN SYNTHESISBASALGRANULARENDOPLASMICRETICULUM MI TOCHONDRIA AND'OLGICOMPLEXES&IGURES! " THESEAREREQUIREMENTSOFPROGRAMMEDCELLDEATHSINCE APOPTOSISISDEPENDENTONTHEEXPRESSIONOFNEWGENES BEINGENCODEDINTHE$.!OFTHETARGETCELL)NSPECI MENS lXED WITH TANNIC ACID THE PRESENCE OF DARKLY STAINEDFOLLICULARCELLSSCATTEREDAMONGCLEARCELLSMAY INDICATETHEPRESENCEOFDAMAGEDCELLS HERALDINGTHEIR EVENTUALDISINTEGRATION&IGURE# &OLLICULARCELLS DESTINEDFORDESTRUCTIONRELEASELARGE ORGANELLE lLLED BLEBS AND PROTRUSIONS THE !0/04/4)# "/$)%3 INTO THE LUMENOFTHEFOLLICLE&IGURE$ 4HESEAREPHAGO CYTOSEDEITHERBYADJACENTHEALTHYFOLLICULARCELLSORBY MONONUCLEARPHAGOCYTES&IGURES% & &OURDAYS AFTERSPAWNING THEBULKOFPOSTOVULATORYFOLLICLESARE REDUCEDBUTNOTCOMPLETELYREABSORBED "ECAUSE OF A SUSPECTED ROLE IN HORMONAL PRODUC TION THEFATEOFPOSTOVULATORYFOLLICLESOFlSHHASRE CEIVED CONSIDERABLE ATTENTION #9#,/34/-%3 ,YGNES ,EWISAND-C-ILLAN 0ATZNER +OS MATH 0ATZNER AND !DAM A B %,!3-/"2!.#(3 (ISAW AND (ISAW ,ANCE AND #ALLARD 4E7INKEL &ASANO 0IERANTONI AND #HIEFl 4%,%/3432AI ,EHRI 0ANT 3HRIVASTAVA .ICHOLLSAND-APLE +HOO .AGAHAMA #HAN AND (OAR .AGAHAMA #LARKE AND(OAR 3ZÚLLÚSI *ALABERT AND"RETON VANDEN(URKAND0EUTE +AGAWA AND4AKANO +AGAWA 4AKANO AND.AGAHAMA ,ANG A 4HEREISGREATSIMILARITYINTHEDE SCRIPTIONS)NMANYSPECIESTHEREISAPROLIFERATIONOF FOLLICULARCELLSWHICHBECOMEPHAGOCYTIC MUCHINTHE SAMEMANNERASTHOSEOFATRETICFOLLICLES ANDREMOVE

4HELITERATUREONTHEMORPHOLOGYOFAPOPTOSISHASBEENREVIEWED BY(ACKER

DÏBRISLEFTINTHEHOLLOWFOLLICLE&IGURE 4HEFOL LICULARWALLCOLLAPSESINTOITSEMPTYLUMENANDFOLDS OFTHEFOLLICULAREPITHELIUMBECOMEINVADEDBYRICHLY VASCULARTHECALELEMENTS0ROLIFERATIONOFTHEFOLLICULAR CELLSCONTINUESAND INAFEWSPECIES PROLIFERATIONOF THECALCELLSISALSODESCRIBED)N3QUALUSACANTHIAS A CORPUS LUTEUM DEVELOPS FROM POSTOVULATORY FOLLICLES BYHYPERTROPHYOFTHEFOLLICULARCELLSSURROUNDEDBYA SEPARATETHECALSHEETBUT IN3CYLIORHINUSSTELLARISAND SEVERAL SPECIES OF 2AJA IT IS FORMED BY HYPERTROPHY OFBOTHTHECALANDFOLLICULARCELLS&ASANO 0IERANTONI AND#HIEFl 3INCETHEREAPPEARSTOBECONTINU OUSSECRETIONOFYOLKBYTHEFOLLICULAREPITHELIUMLONG AFTERTHEOVUMHASBEENDISCHARGED ATLEASTINSOME ELASMBOBRANCHS CARE MUST BE EXERCISED IN DISTIN GUISHINGTHECORPORALUTEAOFATRESIAFROMTHOSERESULT INGFROMOVULATION(ISAWAND(ISAW 4HECALCELLSAPPEARTOPARTICIPATEINTHEPHAGOCYTIC CLEANUPOFPOSTOVULATORYFOLLICLESOFTHETROUT3ALMO GAIRDNERI3ZÚLLÚSI *ALABERT AND"RETON 7ITH INTOHOURSOFOVULATION STELLATETHECALCELLSBE GIN PHAGOCYTOSIS OF ADJACENT COLLAGEN THEIR SLENDER PROCESSESPENETRATINGTHESURROUNDINGCONNECTIVETIS SUESPACE&IGURE$ 4HENUMBEROFPHAGOCYTIC VESICLES WITHIN THE THECAL CELLS INCREASES WITH TIME 7ITHIN A FEW HOURS OF OVULATION mATTENED SMOOTH MUSCLECELLSOFTHETHECATRANSFORMINTOSTELLATECELLS WITHMANYAMOEBOIDPROCESSESTHATISOLATEANDPHAGO CYTOSEBUNDLESOFCOLLAGEN 7HEN THE DÏBRIS HAS BEEN REMOVED FROM THE LU MEN THE CORPUS LUTEUM MAY BECOME ORGANIZED INTO A COMPACT STRUCTURE OF IRREGULAR SHAPE!T THIS STAGE IT IS IMPOSSIBLE TO DISTINGUISH POSTOVULATORY CORPORA LUTEAFROMTHOSEDERIVEDFROMATRESIAOFLARGEFOLLICLES ,UTEALBODIESREMAININGFROMTHEATRESIAOFSMALLFOL LICLES ALSO RESEMBLE POSTOVULATORY FOLLICLES DIFFERING ONLY IN THEIR SMALLER SIZE %VENTUALLY THE FOLLICULAR CELLS DEGENERATE LEAVING A SOLID COMPACT MASS THAT lNALLY DISAPPEARS 4HE SURROUNDING THECAL ELEMENTS AND BLOOD VESSELS ALSO DISAPPEAR 0OSTOVULATORY COR PORALUTEAARENOTFOUNDINTHEMUDEEL !MPHIPNOUS CUCHIA SINCETHEEVACUATEDFOLLICLESDISAPPEARINTHE STROMA WITH hBEWILDERING RAPIDITYv 2ASTOGI )NTHEVIVIPAROUSGUPPY0OECILIARETICULATA FERTILIZA TIONANDGESTATIONTAKEPLACEWITHINTHEFOLLICULARWALL ANDPOSTOVULATORYCORPORALUTEAARENOTFOUND,AM BERT 3TEROIDOGENESIS HAS BEEN DETECTED IN POSTOVULA TORYFOLLICLESOFSEVERALSPECIESOFlSH BOTHOVIPAROUS .ICHOLLSAND-APLE +HOO .AGAHAMA

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#HAN AND (OAR AND VIVIPAROUS ,ANCE AND #ALLARD )N SOME SPECIAL THECAL CELLS REACT POSITIVELY FOR ` (3$ AND SHOW THE ULTRASTRUCTURAL CHARACTERISTICSOFSTEROIDOGENESIS"ARA +AGA WA 4AKANO AND.AGAHAMA INOTHERS ITISTHE FOLLICULARCELLS,AMBERT A+AGAWAAND4AKANO )NSOMElSH BOTHCELLTYPESAPPEARTOCONTRIB UTEACTIVELYTOSTEROIDOGENESIS WITHTHESPECIALTHECAL CELLS SOMETIMES APPEARING TO BE MOST ACTIVE 9ARON .ICHOLLSAND-APLE +HOO .AGA HAMA #HAN AND(OAR VANDEN(URKAND0EUTE 3MITHAND(ALEY )NTHEFEWlSHIN WHICHTHEPOSTOVULATORYFOLLICLESHAVEBEENSTUDIEDAT ANEXTENDEDINTERVALFOLLOWINGOVULATION STEROIDOGEN ESISAPPEARSTOSUBSIDEWITHTIME,ANCEAND#ALLARD .OEVIDENCEWASFOUNDFORSTEROIDOGENESISIN POSTOVULATORYFOLLICLESOFTHEVIVIPAROUSSMOOTHDOG lSH-USTELUSCANIS4E7INKEL &OUR STAGES IN THE LIFE OF A POSTOVULATORY FOLLICLE HAVEBEENDESCRIBEDIN0ERCAmUVIATILIS&IGURES AND ,ANG A 34!'% 2%/2'!.):!4)/. 0(!3% &OR TWO DAYS FOL LOWINGOVULATIONTHEREISAREORGANIZATIONOFTHEDISOR GANIZEDFOLLICULAREPITHELIUM3OMEOFITSCELLSBECOME PHAGOCYTIC THEY CONTAIN LYSOSOMES AND RESORB FOL LICULARCELLSTHATHAVELOSTCONTACTWITHTHEBASEMENT MEMBRANE OR HAVE BEEN DAMAGED DURING OVULATION &IGURE /THERCELLSOFTHEFOLLICULAREPITHELIUM TRANSFORMINTOSYNTHETICALLYACTIVECELLS 34!'% 6!#5/,!20(!3%&ROMDAYSTOFOLLOW INGOVULATION THEFOLLICLEPREPARESITSELFFORSECRETION 34!'% ',/"5,!2 0(!3%&ROMABOUTTODAYS FOLLOWINGOVULATION THEPRESENCEOFAGRANULARENDO PLASMICRETICULUM MITOCHONDRIAWITHTUBULARCRISTAE AND` (3$ACTIVITYARECONSISTENTWITHTHECONCEPT THATTHEFOLLICULARCELLSARESTEROIDOGENIC4HEYENLARGE ANDFORMVACUOLES UPTOMINDIAMETER CONTAIN ING PROTEINACEOUS AND CHOLESTEROL RELATED MATERIAL 4HESE VACUOLES APPEAR TO BE SHED AS A HOLOCRINE SE CRETIONINTOTHEFOLLICULARLUMEN4HELUMENMAYAP PEARASAREDSPOTDUETOTHEPRESENCEOFERYTHROCYTES 4HECALCELLSDONOTEXHIBITANYSTRUCTURALEVIDENCEOF SECRETIONANDSHOWNO` (3$ACTIVITY 34!'% 2%'2%33)/. 0(!3%4HEFOLLICULARCELLSRE MAINING AFTER SECRETION DEGENERATE NO YELLOW PIG MENTSAREFORMED 4HE FORMATION OF A POSTOVULATORY CORPUS LUTEUM HAS BEEN DESCRIBED IN THE CICHLID #ICHLASOMA NIGRO FASCIATUM.ICHOLLSAND-APLE )NTHISSPECIES THEMANIFESTATIONSOFSTEROIDOGENESISAREAPPARENTIN

BOTHTHEFOLLICULAREPITHELIUMANDTHECA4HEBASICOR GANIZATIONOFTHEPREOVULATORYFOLLICLESREMAINSAFTER OVULATION AND THE THECAL LAYERS WITH THEIR CAPILLARIES REMAININTACTFORATLEASTDAYS STILLSEPARATEDFROM THE FOLLICULAR EPITHELIUM BY ITS BASEMENT MEMBRANE 4HE ULTRASTRUCTURE OF PRESUMED STEROIDOGENIC CELLS OFTHETHECAREMAINSUNCHANGEDDURINGTHISTIMEAND PENETRATIONOFTHECALELEMENTSINTOTHEFOLLICULARLAYER APPARENTLYDOESNOTOCCUR&OLLICULARCELLSPROLIFERATE RAPIDLY ATTAINING A THICKNESS OF UP TO FOUR LAYERS OF CELLSBYONEHOURAFTEROVIPOSITIONPRESUMABLYONLYA FEWHOURSAFTEROVULATION 4HEINNERMOSTCELLS INPAR TICULAR TENDTOBECOMECOLUMNARANDTOBULGEINTOTHE REGIONVACATEDBYTHEOOCYTE4HISPROLIFERATIONTHROWS THEBASEMENTMEMBRANEINTOFOLDS4HEENDOPLASMIC RETICULUMOFTHEFOLLICULARCELLSDISSOCIATESITSELFFROM RIBOSOMESANDBYHOURSAFTEROVIPOSITIONTHEFOL LICULARCELLSAREPACKEDWITHLARGEQUANTITIESOFSMOOTH MEMBRANE LARGELYTUBULARAGRANULARENDOPLASMICRE TICULUM -ITOCHONDRIA LIE BETWEEN THE MEMBRANES !LSOPRESENTAREFREEPOLYRIBOSOMES OCCASIONALLIPID DROPLETS AND INCLUSIONS TENTATIVELY IDENTIlED AS LI POFUSCIN 3OME CELLS CONTAIN A LARGE 'OLGI COMPLEX CONSISTING OF SEVERAL INDIVIDUAL LAMELLAR STACKS AND ASSOCIATED VESICLES ! FEW DAYS AFTER SPAWNING DE GENERATIVE PROCESSES APPEAR WITHIN THESE POSTOVULA TORY FOLLICLES ALTHOUGH COMPARABLE DEGENERATION OF THE THECA WAS NOT OBSERVED EVEN DAYS FOLLOWING OVIPOSITIONWHENTHEPRESUMEDSTEROID SECRETINGTHE CALCELLSARESTILLCLUSTEREDCLOSETOCAPILLARIESANDMAY CONTINUESECRETINGSTEROIDHORMONESDURINGTHISTIME 4HEFOLLICULARCELLS HOWEVER SEEMTOBEACTIVELYSE CRETORY FOR ONLY A FEW DAYS THEIR LARGE AMOUNTS OF SMOOTHMEMBRANETHENSEEMTOBECOMEDISORGANIZED ANDGRADUALLYDISAPPEARWHILEQUANTITIESOFDEPOSITED LIPIDSAPPARENTLYINCREASE 0OSTOVULATORYFOLLICLESOFTILAPIA/REOCHROMISMOS SAMBICUS ARE THE MOST PROMINENT STRUCTURES IN THE OVARY FOR TO DAYS AFTER SPAWNING WHEN THE NEXT CLUTCHOFEGGSBEGINSTOGROW&IGURE! 3MITH AND(ALEY /NTHElRSTDAYAFTERSPAWNINGOC CASIONALCAPILLARIESARESCATTEREDTHROUGHOUTTHETHECA !BOUT EIGHT PERCENT OF THE CELLS OF THE THECA INTERNA APPEAR STEROIDOGENIC DISPLAYING AGRANULAR ENDOPLAS MICRETICULUMUSUALLYTUBULAR ANDMITOCHONDRIAWITH TUBULAR CRISTAE &IGURES # $ AND ! !LSO PRESENTINTHESECELLSAREGRANULARENDOPLASMICRETICU LUM FREE RIBOSOMES MICROlLAMENTS AND OCCASIONAL LIPIDDROPLETS4HECELLSOFTHETHECAEXTERNAASWELLAS THE NON STEROIDOGENIC CELLS CELLS OF THE THECA INTERNA

#(!04%2

ARE lBROBLASTIC WITH CYTOPLASM CONTAINING GRANULAR ENDOPLASMIC RETICULUM FREE POLYRIBOSOMES AND MI CROlLAMENTS #ELLS OF THE THECA EXTERNA ARE WIDELY SEPARATEDFROMONEANOTHEREACHISATTACHEDTOACELL OFTHETHECAINTERNABYAFEWDESMOSOMESANDLARGE INTERCELLULAR SPACES OPEN BETWEEN THE POINTS OF AT TACHMENT&IGURE" &OLLICULARCELLSARECUBOIDAL WITHLOBEDNUCLEI&IGURE" 4HECELLSAREPACKED WITH ABUNDANT AGRANULAR ENDOPLASMIC RETICULUM THAT APPEARSVESICULAR3OMEGRANULARENDOPLASMICRETICU LUM OCCURS BASALLY AND FREE RIBOSOMES ARE SCATTERED THROUGHOUT -ITOCHONDRIAL CRISTAE ARE LARGELY LAMEL LAR &IGURE # 4HE APICAL SURFACE OF THESE CELLS BULGESINTOTHELUMENPROMINENTDESMOSOMESATTACH THEAPICOLATERALSURFACES4HEAPICALSURFACEISREGULAR WITHFEWMICROVILLIMANYVESICLESAREFUSEDWITHITS INNERPLASMALEMMA/CCASIONALBLOODCELLSAPPEARIN THELUMEN"YTODAYSAFTERSPAWNING THEFOLLICU LARCELLSAREUSUALLYCOLUMNARWITHAPICALMICROVILLI VESICLESAPPEARFUSEDTOTHEINNERSURFACEOFTHEAPICAL PLASMALEMMA&IGURE %ACHCELLCONTAINSSEVER ALMODERATELYDEVELOPED'OLGICOMPLEXESANDASMALL AMOUNT OF TUBULAR AGRANULAR ENDOPLASMIC RETICULUM 3OMEMICROTUBULESAREFOUNDANDTHENUMBEROFMI CROlLAMENTSISINCREASED!FEWMULTIVESICULARBODIES ARESEEN-OSTMITOCHONDRIACONTAINLAMELLARCRISTAE BUTAFEWTUBULARCRISTAEAREOCCASIONALLYPRESENT)TIS POSSIBLETHATASTEROIDHORMONEPRODUCEDINTHETHECAL CELLSMAYBEFURTHERCONVERTEDTOOTHERSTEROIDSBYEN ZYMESINTHEAGRANULARENDOPLASMICRETICULUMOFTHE FOLLICULAR CELLS 4HE PRIMARY SITE OF STEROIDOGENESIS HOWEVER APPEARSTOBEINTHESPECIALTHECALCELLS 0OSTOVULATORY FOLLICLES OF VARIOUS SALMONIDS HAVE AFOLDEDFOLLICULAREPITHELIUMTHATISCONTINUOUSWITH THECOELOMICEPITHELIUMOFTHELAMELLAE&IGURES) AND # .AGAHAMA #LARKE AND (OAR 3ZÚLLÚSI *ALABERT AND "RETON VAN DEN (URK AND 0EUTE +AGAWA 4AKANO AND .AGAHAMA 3TRONG` (3$ACTIVITYISPRESENTINTHELARGE NUMBERS OF SPECIAL THECAL CELLS ARRANGED AROUND THE YOUNGPOSTOVULATORYFOLICLE BUTONLYWEAKACTIVITYIN THEFOLLICULARCELLS&IGURES!AND! " %LEC TRONMICROGRAPHSOFTHESESPECIALTHECALCELLSSHOWTHE PRESENCEOFABUNDANTAGRANULARENDOPLASMICRETICULUM AND TUBULAR MITOCHONDRIAL CRISTAE &IGURES " # # $ 4HESEFEATURESALSOAPPEAR TOSOMEEXTENT INTHEFOLLICULARCELLSOFYOUNGPOSTOVULATORYFOLLICLES OFTHERAINBOWTROUT 3ALMOGAIRDNERI WHICHALSOAP PEAR TO BE STEROIDOGENIC &IGURES $ % VAN DEN (URK AND 0EUTE )N ADDITION THE FOLLICULAR

CELLS EXHIBIT WELL DEVELOPED 'OLGI COMPLEXES MANY LYSOSOME LIKE STRUCTURES COATED VESICLES AND ELEC TRON DENSE VESICLES ,ATER THESE MANIFESTATIONS OF STEROIDOGENESIS ARE REDUCED "OTH SPECIAL THECAL AND FOLLICULAR CELLS OF POSTOVULATORY FOLLICLES SYNTHESIZE STEROIDS THAT MAY BE RELATED TO THE DEVELOPMENT OF NEWFOLLICLES4HESPECIALTHECALCELLSOFTWOSPECIES OFSALMON/NCORHYNCHUSSPP AREDESCRIBEDASSTE ROIDOGENICWHILETHEFOLLICULARCELLSAPPEARDEGENERATE .AGAHAMA #LARKE AND(OAR "YONEMONTH AFTEROVULATION SPECIALTHECALCELLSOFTHEWHITE SPOT TEDCHAR3ALVELINUSLEUCOMAENISSTILLPOSSSESSTHECEL LULARORGANELLESTYPICALOFSTEROIDOGENESISBUTAPPEAR TOBEUNDERGOINGDEGENERATION+AGAWA 4AKANO AND .AGAHAMA )N THE !FRICAN CATlSH #LARIAS GARIEPINUS WHERE OVARIESOFUNSTRIPPEDlSHMAYCONTAINOVERRIPEEGGS WITHIN THE OVARIAN CAVITY HYPERTROPHIED FOLLICULAR CELLSCONTAINHETEROPHAGICLYSOSOMESANDAREACTIVELY PHAGOCYTIC REMOVING MATERIAL OF THE DISINTEGRATING OVULATEDEGGS&IGURE VANDEN(URKAND0EUTE %VENTUALLYAUTOPHAGICLYSOSOMESTAKEPARTIN THEDEGRADATIONOFTHECONTENTSOFTHEFOLLICULARCELLS AND ARE ULTIMATELY RESPONSIBLE FOR THE DISINTEGRATION OFTHEPOSTOVULATORYFOLLICLE)TISSUGGESTEDTHATDIS INTEGRATING OVERRIPEEGGSRELEASECOMPOUNDSTHATIN HIBIT THE PRODUCTION OF STEROIDS BY FOLLICULAR CELLS OF THEPOSTOVULATORYFOLLICLES THEREBYSTOPPINGTHEPRO DUCTION OF SEX PHEROMONES AND AVOIDING A POTENTIAL SPAWNING SINCE FERTILIZATION OF OVERRIPE EGGS MIGHT LEADTOBIRTHOFDEFORMEDFRY 4RUECORPORALUTEADEVELOPINBOTHVIVIPAROUSAND OVIPAROUSELASMOBRANCHS#HIEFl #HIEFl"AC CARIETAL 4HEYDEVELOPFROMATRETICFOLLICLES IN4ORPEDOMARMORATAAND4OCELLATAOVOVIVIPAROUS ANDFROMPOSTOVULATORYFOLLICLESIN3CYLIORHINUSSTEL LARISAND3CANICULAOVIPAROUS !FTERPHAGOCYTOSIS OF THE YOLK IN 4ORPEDO THE FOLLICULAR CELLS UNDERGO HYPERTROPHY AND SHOW CLEAR SIGNS OF LIPID AND STE ROIDMETABOLISM4HUSTHEATRETICFOLLICLEASSUMESTHE STRUCTUREOFATRUEEPITHELIALGLANDWHICHPERSISTSDUR INGSEVERALMONTHSOFGESTATION)N4MARMORATA AN INCREASEINTHENUMBEROFFULLYDEVELOPEDCORPORALU TEACOINCIDENTWITHTHELENGTHENINGOFTHEUTERINEFOLDS DURINGTHEREPRODUCTIVECYCLESUGGESTSANINmUENCEOF THESESTRUCTURESONPREGNANCY0OSSIBLEEFFECTSOFTHE CORPORALUTEAONTHEGENITALTRACTOFTHEOVIPAROUS3CYL IORHINUSISLEFTFORSPECULATION 4HE ORGANIZATION OF CORPORA LUTEA IS SIMILAR IN OVIPAROUSANDVIVIPAROUSELASMOBRANCHSANDCONSISTS

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OFLIPID lLLEDCELLSDERIVEDFROMTHEFOLLICULAREPITHE LIUMARRANGEDAROUNDACENTRALLUMENINEARLYSTAG ES OF LUTEAL FORMATION HYPERTROPHY OF THE CELLS MAY OBSCURE THE LUMEN &IGURE +OOB AND #ALLARD 4HE CELLS CONTAIN LARGE NUCLEI WITH CONSPICU OUSNUCLEOLIANDABUNDANTLIPIDDROPLETSINADDITION THEY MANIFEST THE AGRANULAR ENDOPLASMIC RETICULUM ANDMITOCHONDRIAWITHTUBULARCRISTAECHARACTERISTICOF STEROID PRODUCING CELLS! VASCULAR CONNECTIVE TISSUE STROMAISPROVIDEDBYINGROWTHSFROMTHETHECA4HE CORPORALUTEAOFOVIPAROUSFORMSDECLINEWITHINAFEW WEEKSBUT INVIVIPAROUSSPECIES THEYPERSISTTHROUGH OUTGESTATION$EGENERATIONOFCORPORALUTEAINVOLVES AREDUCTIONINSIZEOFTHESTRUCTURE INCREASEDDISORGA NIZATIONOFTHELOBULES ADECREASEINTHELIPIDCONTENT OFINDIVIDUALCELLS DEATHOFCELLS ANDANACCUMULATION OFCELLULARDÏBRISINTHELUMEN 4HERE IS NO MORPHOLOGICAL INDICATION OF STEROIDO GENESISINPOSTOVULATORYFOLLICLESOF-YXINEGLUTINOSA +OSMATH 0ATZNER AND!DAM A !PERIODOFRE ORGANIZATION WHERETHECELLULARDÏBRISREMAININGAFTER OVULATION IS REMOVED BY PHAGOCYTOSIS IS SOON FOL LOWEDBYREGRESSIONANDDISAPPEARANCEOFTHEFOLLICLE INTHISPHASETHEFOLLICULARCELLSANDTHECADEGENERATE ANDAREREMOVEDBYBLOOD BORNEPHAGOCYTES.OCHO LESTEROL NOR ` (3$ ACTIVITY WAS DETECTED IN THE CELLSOFTHEPOSTOVULATORYFOLLICLE+OSMATH 0ATZNER AND!DAM B

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CLUDINGhSPECIALTHECALCELLSv ANDINTERSTITIALCELLSOF THEOVARY%VIDENCEHASBEENGATHEREDFORALARGENUM BEROFlSHUSINGHISTOCHEMICALTESTSFORTHEPRESENCE OFSTEROIDOGENICENZYMESSUCHAS` HYDROXYSTEROID DEHYDROGENASE` (3$ MORERECENTLYIMMUNOCY TOCHEMICALMETHODSHAVEBEENUSED!LTHOUGHULTRA STRUCTURALEVIDENCEFORSTEROIDOGENESISHASOFTENBEEN RECORDED ITISEQUIVOCAL6ARYINGPATTERNSOFSTEROIDO GENESIS THEREFORE HAVEBEENPROPOSEDFORTHEFOLLICLES OF DIFFERENT GROUPS OF lSH "EARING IN MIND THE VAST RANGE OF REPRODUCTIVE STRATEGIES FOUND IN lSH HOW EVER THISISNOTSURPRISING !N EXPLANATION FOR SOME OF THE DILEMMA AT LEAST FORSALMONIDS ISPROVIDEDBYTHE47/ #%,, 490%-/$%, THATPROPOSESASYNERGISMBETWEENTHETHECALANDFOL LICULARCELLS WHERETHECALCELLSSYNTHESIZETHEPRECUR SORS TESTOSTERONE AND _ HYDROXYPROGESTERONE FOR CONVERSIONBYFOLLICULARCELLSTOTHEHORMONESOESTRA DIOL ` AND _ ` $0 RESPECTIVELY &IGURE +AGAWAETAL .AGAHAMA +AGAWA AND9OUNG .AGAHAMA +ANAMORI !DACHI AND .AGAHAMA )T IS SUGGESTED THAT THE TWO CELL TYPEMODEL ATLEASTFORTHEPRODUCTIONOFOESTRADIOL ` ALSOAPPLIESTOTHEOVARYOFTILAPIA /REOCHROMIS NILOTICUS.AKAMURA 3PECKER AND.AGAHAMA !CCORDING TO THE TWO CELL TYPE MODEL DURING VI TELLOGENESIS THE THECAL LAYERS PRODUCE AROMATIZABLE ANDROGENS MAINLY TESTOSTERONE IN RESPONSE TO GO NADOTROPIN THESE ARE CONVERTED TO OESTRADIOL ` BY AROMATASE ENZYME SYSTEMS PRESENT IN THE FOLLICULAR LAYER+AGAWAETAL .AGAHAMA 9OUNG +AGAWA AND .AGHAMA *UST PRIOR TO OOCYTE MATURATION GONADOTROPIN STIMULATES THECAL LAYERS TO PRODUCE _ HYDROXYPROGESTERONE THIS IS CONVERTED TO _ ` $0 BY FOLLICULAR LAYERS WHERE GONADOTROPIN HAS INDUCED THE ACTIVITY OF ` HY DROXYSTEROIDDEHYDROGENASE THEENZYMEINVOLVEDIN THISCONVERSION.AGAHAMA 9OUNG !DACHI AND .AGAHAMA !SINGLEPOPULATIONOFRECEPTORSFOR GONADOTROPINONBOTHTHECALANDFOLLICULARCELLSOFTHE AMAGO SALMON /NCORHYNCHUS RHODURUS +ANAMORI AND .AGAHAMA A STIMULATE STEROIDOGENESIS BY MECHANISMS INVOLVING ADENYLATE CYCLASECYCLIC !-0C!-0 &IGURE +ANAMORIAND.AGAHA MA B 4HESHIFTINSTEROIDOGENICRESPONSIVENESS OFTHESECELLSTOGONADOTROPINAPPEARSTORESULTFROM ACHANGEINCELLULAREVENTSATASTEPS SUBSEQUENTTO C!-0PRODUCTION 4HE TWO CELL TYPE MODEL PROVIDES AN EXPLANA TION FOR THE SPARSE ULTRASTRUCTURAL AND HISTOCHEMICAL

#(!04%2

EVIDENCE OF STEROIDOGENESIS BY PREOVULATORY FOLLICU LAR CELLS WHICH OFTEN MANIFEST ORGANELLES TYPICAL OF PROTEIN SECRETING CELLS .AGAHAMA #HAN AND (OAR (OARAND.AGAHAMA -ATSUYAMA .AGA HAMA AND-ATSUURA 3INCESEVERALBIOCHEMI CALSTEPSAREINVOLVEDINTHEPRODUCTIONOFTESTOSTERONE BYTHECALCELLS THISISREmECTEDINTHEIRULTRASTRUCTURAL APPEARANCEOFSTEROIDOGENESIS&IGURE 3ELMAN ETAL AROMATIZATIONOFTESTOSTERONETOOESTRA DIOL ` HOWEVER INVOLVESONLYAFEWSTEPSANDTHE ORGANELLES TYPICAL OF STEROIDOGENESIS ARE MASKED BY THOSECARRYINGOUTOTHERACTIVITIESWITHINTHEFOLLICULAR EPITHELIUM+AGAWAETAL )TMAYBENOTEDIN THIS REGARD THAT FOLLICULAR CELLS OF COHO SALMON /N CORHYNCHUSKISUTCH CONTAINSMALLAMOUNTSOFAGRANU LAR ENDOPLASMIC RETICULUM AND MITOCHONDRIA WITH TUBULAR CRISTAE DISTRIBUTED THROUGHOUT THEIR ABUNDANT PROTEIN PRODUCINGORGANELLES.AGAHAMA #LARKE AND (OAR 4HEGENERALIZATIONCANNOTBEMADE HOWEVER THAT THETWO CELL TYPEMODELOPERATESINTHEOVARIESOFALL lSH&OREXAMPLE INTHEKILLIlSH &UNDULUSHETEROCLI TUS FOLLICULARCELLSARETHEPRIMARYSOURCEOFFOLLICU LARSTEROIDSINRESPONSETOPITUITARYSTIMULATIONSOTHAT SYNTHESISOFOESTRADIOL ÀND_ ` $0DOESNOT REQUIRETHEINVOLVEMENTOFTHECALCELLS0ETRINOETAL 4HECALCELLSAPPEARTOBESTEROIDOGENIC HOW EVER INSPITEOFTHEIRNONSTEROIDOGENICAPPEARANCEIT ISSUGGESTEDTHATTHEYSYNTHESIZETESTOSTERONE PROVID INGASECONDSOURCEOFAROMATIZABLESUBSTRATEFORTHE SYNTHESISOFOESTRADIOL `BYFOLLICULARCELLS 4HEREISACOMMONSTEROIDOGENICPATHWAYFORMUCH OFTHESYNTHESISOFTHETWOHORMONESWHICHPLAYSUCH ANIMPORTANTROLEINVITELLOGENESISANDMATURATIONOF OVARIANFOLLICLESINTELEOSTS&IGURE +OBAYASHI ET AL 0RIOR TO OOCYTE MATURATION A DISTINCT SHIFT OCCURS FROM THE PRODUCTION OF OESTRADIOL ` TO _ ` $0 PROBABLY THE RESULT OF A DECREASE IN THEACTIVITYOFTHEENZYME# LYASECYTOCHROME 0 _ HYDROXYLASE# LYASE )TISPRESUMED THATTHEDECREASEINOESTRADIOL `PRODUCTIONWOULD LEADTOANACCUMULATIONOF_ HYDROXYPROGESTERONE THEIMMEDIATEPRECURSOROF_ ` $0 4HREE STEROID HORMONES PLAY A SIGNIlCANT ROLE IN REGULATING THE WIDE RANGE OF REPRODUCTIVE STRATE GIES SEEN IN FEMALE ELASMOBRANCHS OESTRADIOL ` TESTOSTERONE AND PROGESTERONE 4SANG AND #ALLARD #ALLARD ET AL +OOB AND #ALLARD #ALLARD &ILETI AND +OOB /ES TRADIOL ` AND TESTOSTERONE ARE ASSOCIATED WITH FOL

LICULARDEVELOPMENTWHILEPROGESTERONEPLAYSAROLEIN EGG RETENTION AND PREGNANCY!S WOULD BE EXPECTED THEAMOUNTSOFTHESESTEROIDSINTHECIRCULATIONmUCTU ATEWITHTHESTAGEINTHEREPRODUCTIVECYCLE)SOLATED FOLLICULAREPITHELIALCELLSOFSEVERALSPECIESSYNTHESIZE SIGNIlCANT QUANTITIES OF TESTOSTERONE OESTRADIOL ` AND PROGESTERONE WITHOUT REQUIRING THECAL ELEMENTS 4HECAL TISSUE ALONE IN THE PRESENCE OF TESTOSTERONE ISABLETOSYNTHESIZEOESTRADIOL ÀNDANINTERACTION BETWEENFOLLICULARANDTHECALLAYERSINVIVOISSUGGEST ED4ESTOSTERONEISTHEPREDOMINANTPRODUCTOFTHECAL CELLS AND IS ALSO PRODUCED BY THE CORPORA LUTEA4HE CORPORALUTEAARETHEPRINCIPALSOURCEOFPROGESTERONE INBOTHVIVIPAROUSANDOVIPAROUSSPECIES #ONmICTINGPICTURESOFOVARIANSTEROIDOGENESISARE SEEN WITHIN THE CYCLOSTOMES .O ` (3$ WAS DE TECTED IN THE OVARY OF -YXINE GLUTINOSA NOR DID THE CELLS OF ITS FOLLICLE REVEAL ANY ULTRASTRUCTURAL FEATURES INDICATIVE OF STEROID PRODUCTION &ERNHOLM 4SUNEKI AND 'ORBMAN 4HE MATURE OVARY OF %PTATRETUSBURGERI HOWEVER ISCAPABLEOFARANGEOF STEROID BIOCONVERSIONS WHEN INCUBATED IN VITRO WITH VARIOUSPRECURSORS(IROSEETAL )TISNOTCLEAR WHETHERTHISISAREALDIFFERENCEBETWEENTHETWOSPE CIESORDIFFERENCEINTHESENSITIVITIESOFTHETECHNIQUES USED 4HE THECA INTERNA OF THE PRIMARY FOLLICLE OF ,AMPETRA PLANERI DIFFERENTIATES DURING METAMORPHO SIS )TS CELLS MANIFEST THE CHARACTERISTIC APPEARANCE OF STEROIDOGENESIS SOME TIME BEFORE VITELLOGENESIS CONTAININGABUNDANTAGRANULARENDOPLASMICRETICULUM ANDLIPIDDROPLETS"USSON -ABILLOT TENTATIVE HISTOCHEMICALANDSPECTROPHOTOMETRICEVIDENCEOFHY DROXYSTEROIDDEHYDROGENASEACTIVITYHASBEENNOTEDIN THESECELLS3EILER 3EILER AND#LAUS )NTHEOVA RYOFTHESEALAMPREY0ETROMYZONMARINUS HOWEVER NOCLEARLYDElNEDSTEROIDOGENICCELLTYPESWEREFOUND ANDNO` (3$WASDETECTED7EISBART 9OUSON AND 7IEBE 4HECELLSOFTHETHECAINTERNAOFTENCON TAINEDLARGELIPIDDROPLETSINTHEIRCYTOPLASM&IGURE BUTTHESECELLSDIDNOTPOSSESSOTHERCHARACTERIS TICSOFSTEROID PRODUCINGCELLS

+OOBAND#ALLARD HAVEPROVIDEDANOVERVIEWOFTHE SPECTRUMOFREPRODUCTIVEMODESTOGETHERWITHSPECULATIONONTHEIR HORMONALREGULATIONASSEENINFEMALEELASMOBRANCHS

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#HORION

!S VITELLOGENESIS ENDS AND THE OOCYTE IS READY FOR OVULATION THE ZONA PELLUCIDA CHANGES ULTRASTRUCTUR ALLY AND PERHAPS CHEMICALLY 4HE PRIMARY ENVELOPE BECOMESTHINNERANDTHEOUTERMOSTZONEISOFTENLOST THE ELABORATE lBRILLAR PATTERNS FADE INTO A HOMOGE NEOUS TRANSLUCENTZONE4HEhARABESQUEvPATTERNSARE TRANSFORMEDATOVULATIONANDTHECHORIONASSUMESTHE WOVENAPPEARANCE$UMONTAND"RUMMETT OF A lBROUS LAMINATE THAT STRENGTHENS THE LAYER BY ACT ING EQUALLY IN ALL DIRECTIONS TO ACCOMMODATE TENSILE STRESSES&IGURE! 'RIERSONAND.EVILLE 4HISTRANSFORMEDPRIMARYENVELOPEISSOMETIMESCOV EREDBYTHESECONDARYENVELOPETHATMAYBEELABORATE LYORNAMENTED&IGURE" 4HEOUTERCOVERINGOF THEEGGISNOWA#(/2)/. !LTHOUGHTHETERMhCHORIONvHASBEENUSEDINSEV ERAL WAYS IT MAY BE DElNED AS THE ACELLULAR HIGHLY STRUCTURED ENVELOPE ENCLOSING AN OVULATED EGG OR DEVELOPING EMBRYO SEPARATING IT FROM THE EXTERNAL ENVIRONMENT (ART 0IETRI AND $ONOVAN 4HE CHORIONISUSUALLYPERFORATEDBYAPASSAGE THE-)#2/ 09,% THROUGH WHICH A SPERMATOZOON GAINS ACCESS TO THE OOPLASMIC SURFACE AND EFFECTS FERTILIZATION 4HE OUTERSURFACEISOFTENADORNEDWITHSPECIALIZATIONSIN THEFORMOFTHREADS lLAMENTS lBRILS ORSPIKES 4HE CHORION IS SOFT WITHIN THE OVARY BUT IT BEGINS TO HARDEN FOLLOWING OVULATION !FTER FERTILIZATION IT SEPARATESFROMTHESURFACEOFTHEOOCYTEANDHARDEN INGCONTINUES0ENETRATIONBYTHESPERMATOZOONBRINGS ABOUTANINCREASEINCALCIUMCONTENTOFTHEPERIPHERAL OOPLASM CAUSINGTHECORTICALALVEOLITOFUSEWITHTHE OOLEMMATHEhCORTICALREACTIONvBEGINNINGATTHE SITEOFSPERMENTRYANDPROCEEDINGASAWAVEOVERTHE SURFACEOFTHEEGG5PONFUSION THEVESCLESDISCHARGE THEIRCONTENTSINTOTHESPACEBETWEENTHEPLASMAMEM BRANE AND THE CHORION THE 0%2)6)4%,,).% 30!#% !N ACIDICGLYCOSAMINOGLYCANTHATISTOOLARGETOPENETRATE THECHORIONISRELEASED THEREBYCAUSINGANINCREASEIN THEOSMOLARITYOFTHEPERIVITELLINEmUIDRELATIVETOTHE SURROUNDINGS 3INCE THE CHORION IS PERMEABLE TO WA TERANDSMALLELECTROLYTES THEREISANINmUXOFWATER INCREASINGTHEHYDROSTATICPRESSUREINTHEPERIVITELLINE SPACEANDFORCINGTHEELASTICCHORIONTOEXPANDAWAY FROMTHEPLASMAMEMBRANE3UBSEQUENTLY THECHORION LOSESITSELASTICITYANDBECOMESTOUGHANDRIGIDINTHE PROCESSOFHARDENING4HEHARDENEDCHORIONSERVESTO PROTECTTHEEGGFROMMECHANICALDAMAGEANDMICRO BIALATTACK

)N SOME SPECIES THE MICROVILLI FROM BOTH OOCYTE ANDFOLLICULARCELLSWITHDRAWFROMTHEPORECANALSAND THEOUTEROPENINGSMAYBECOMEBLOCKEDWITHhPLUGSv &IGURES " # &LàGEL A B 3TEHR AND (AWKES $UMONT AND "RUMMET (ART AND$ONOVAN )NSOMESALMONIDS HOWEVER THE MICROVILLIDONOTWITHDRAWANDHAVEBEENOBSERVEDIN THE PORE CANALS OF OVULATED EGGS 3CHMEHL AND 'RA HAM )N THE ZEBRA DANIO "RACHYDANIO RERIO MOSTOFEACHPORECANALREMAINSOPENEXCEPTFORTHE PLUG PRESUMABLY DEPOSITED ON THE WITHDRAWAL OF THE MICROVILLI BY A MECHANISM NOT UNDERSTOOD (ART AND$ONOVAN 2EMNANTS OF THE PRIMARY ENVELOPE PERSIST AS A l BROUS LAMELLARCOATINTHECHORIONOFAWIDERANGEOF SPECIES4HISMAYBESURROUNDEDBYJELLYCOATS lLA MENTS ANDORNAMENTATIONPROVIDEDBYTHESECONDARY ENVELOPE!SIMPLECHORION SAIDTOBEDERIVEDSOLELY FROMTHEPRIMARYENVELOPEISFOUNDONTHEEGGOFTHE ZEBRA DANIO (ART AND $ONOVAN )T IS TO MTHICKANDCONSISTSOFTHREEZONESPORECANALS PENETRATE THE INNER TWO ZONES ONLY &IGURE ! 4HE/54%2,!9%2ISABOUTMTHICK HOMOGENEOUS ELECTRON DENSE AND EVENLY DISPERSED OVER THE SUR FACEITISADORNEDWITHPROMINENTPROJECTIONS&IGURE # $ISTINCT PLUGS OF OSMIOPHILIC MATERIAL BLOCK THE OUTER OPENING OF EACH PORE CANAL AT THIS LEVEL &IGURE " 4HE -)$$,% ,!9%2 ABOUT M THICK ISOFMEDIUMELECTRONDENSITYANDHASACOM PACT lBRILLAR APPEARANCE 4HE lBRES ABOUT TO M IN DIAMETER ARE ORGANIZED IN CRISSCROSSING BUNDLESAROUNDTHEPORECANALS4HE)..%2,!9%2COM PRISESMOSTOFTHECHORIONANDCONSISTSOFHORIZONTAL ELECTRON DENSE LAMELLAE OF ABOUT EQUAL THICKNESS AL TERNATINGWITHINTERLAMELLARPORTIONSOFLOWERDEN SITY4HECENTRE TO CENTRESPACINGOFTHEPORECANALSIS M 4HEIR DIAMETER JUST BELOW THE PLUG IS ABOUT M WIDENING TO OR M AT THE INSIDE 4HEREAREABOUTXPORECANALSPEREGG 4HE INNER LAYERS OF THE CHORION OF THE MEDAKA /RYZIAS LATIPES ARE SIMILAR TO THE CHORION OF THE ZE BRADANIO EXCEPTTHATTHESEAREENCLOSEDINAlLAMEN TOUSCOATDERIVEDFROMTHESECONDARYENVELOPE(ART 0IETRI AND$ONOVAN )WAMATSU 4HECHO RIONISABOUTTOMTHICKANDCONSISTSOFTHREE DISTINCTZONESAN /54%2 :/.% FUZZY ELECTRON LUCENT ABOUT M THICK A -)$$,% :/.% HOMOGENEOUS ELECTRON DENSE ABOUTMTHICK WITHANIRREGULAR INNER BORDER AND AN )..%2 :/.% FORMED OF TO ELECTRON DENSELAMELLAEALTERNATINGWITHINTERLAMELLAE

#(!04%2

OFLOWERELECTRONDENSITY&IGURES! " 4HEOUTER SURFACEOFTHECHORIONISRAISEDINTOAUNIFORMINTERCON NECTINGSYSTEMOFRIDGESINAPATTERNOFHEXAGONSAND PENTAGONSPRESUMABLYTHISPATTERNISANIMPRESSIONOF THEFOLLICULAREPITHELIUM REPRESENTINGANOUTLINEOFTHE CELLSANDTHEIRINTERCELLULARSPACES&IGURES# ) 4HE CHORION IS ADORNED WITH TWO TYPES OF lLAMENTS PRODUCED BY THE FOLLICULAR EPITHELIUM !BOUT TO !44!#().' &),!-%.43 ORIGINATE FROM THE VEGETAL POLEAREAOFTHECHORION INTERTWININGTIGHTLYTOFORM A ROPELIKE CORD &IGURE ) THAT JOINS WITH CORDS FROMNEIGHBOURINGEGGSTOFORMACLUSTERSUSPENDED WITHINTHEGONODUCT4HEREMAINDEROFTHECHORIONIS COVEREDBY./.!44!#().'&),!-%.43OFVARIABLELENGTH SOMEARESHORTANDSTUBBYWHILEOTHERSTAPERINTOLONG THREADLIKE PROCESSES THAT INTERTWINE WITH lLAMENTS ON ADJACENT EGGS PRODUCING A GOSSAMER NETTING THAT SERVESTOMAINTAINTHEINTEGRITYOFTHEEGGCLUSTER"OTH TYPES OF lLAMENTS ARE FORMED OF DENSELY PACKED TU BULESMICROTUBULESORhMICROTUBULEMIMICSv WITHAN AVERAGE OUTSIDE DIAMETER OF APPROXIMATELY AND NMRESPECTIVELY&IGURES%TO( (ART 0IE TRI AND$ONOVAN 4HEWALLOFEACHMICROTUBULE ISCYLINDRICALANDISCOMPOSEDOFGLOBULARSUBUNITSAR RAYEDINLONGITUDINALROWS&OURTEENOFTHESESTRUCTUR ALSUBUNITSARERANGEDAROUNDTHEWALLOFEACHTUBULE )NMATUREOOCYTESOFTHEMEDAKA/RYZIASLATIPES THE LONGATTACHINGlLAMENTSAREWOUNDSPIRALLYONTHEAXIS BETWEEN THE ANIMAL AND VEGETAL POLES &IGURE )WAMATSU 4HE SHORT NON ATTACHING lLAMENTS DISTRIBUTEDONTHERESTOFTHECHORIONICSURFACE AREALSO BENTINAUNILATERALDIRECTIONONTHEEGGAXIS4HISSPI RALING CAN BE EITHER RIGHT HANDED OR LEFT HANDED AND ISESTABLISHEDEARLYINOOGENESIS)TAPPEARSNOTTOBE ANINHERITEDPATTERNBUTISIMPOSEDDURINGOOGENESIS BYROTATIONOFTHEOOCYTEANDITSFOLLICULAREPITHELIUM WITHINTHEBASEMENTMEMBRANE #ROSS FRACTURES THROUGH THE GLUTARALDEHYDE lXED CHORIONOF/RYZIASINDICATETHATTHELAMELLAEARESHEETS OF TIGHTLY PACKED INTERWOVEN lBRES OFTEN ENCLOSING TEARDROP SHAPED CAVITIES MEASURING ABOUT BY M(ART 0IETRI AND$ONOVAN 4HELAYERINGOF THESE lBROUS SHEETS IS PRESUMABLY THE STRUCTURAL AND PHYSICALBASISFORMECHANICALSTABILITYANDTOUGHNESS 4HE lBRES APPEAR TO BE FORMED OF A HETEROGENEOUS FAMILY OF HIGH MOLECULAR WEIGHT GLYCOPROTEINS 4HE SMALL TEARDROP SHAPED HOLES MAY REPRESENT REMNANTS OF THE PORE CANALS 4HE LAMELLAE OF THE INNER ZONE OF /RYZIAS ARE CONTINUOUS AND UNINTERRUPTED BY PAT ENT PORE CANALS 4HE INNER SURFACE OF THE CHORION IS

PEBBLED WITH REGULARLY SPACED BULGES FORMED BY THE BULBLIKE BASES OF BOTH TYPES OF lLAMENTS WHICH ARE lRMLYROOTEDWITHINTHELAMELLAEOFTHEINNERZONEOF THECHORION&IGURE$ !NALYSESOFTHEPROTEINSOFTHECHORIONHAVEUTILIZED THE (!4#().' %.:9-% APROTEOLYTICENDOPROTEASETHAT BREAKSDOWNTHECHORIONDURINGHATCHING3CHOOTSET AL )NTHEANNUALlSH.OTHOBRANCHIUSKORTHAU SAE WHICH HAS A RELATIVELY THICK ENVELOPE THE INNER ZONE OF THE CHORION IS ENTIRELY DIGESTED BUT IN THE PIKE%SOXLUCIUSANDTHEZEBRA lSH"RACHYDANIORERIO WHICHHAVETHINENVELOPES ADECREASEINTHICKNESSOF ONLYANDRESPECTIVELYISOBSERVED4HEIN NERLAYEROFTHECHORIONAPPEARSTOBETHENATURALSUB STRATEFORTHISENZYME(ISTOCHEMICALANDBIOCHEMICAL INVESTIGATIONS UTILIZING THIS ENZYME HAVE SHOWN THAT THEINNERLAYERCONSISTSOFPROTEINSANDGLYCOPROTEINS (AGENMEIER )UCHIAND9AMAGAMI /N THE BASIS OF BIOCHEMICAL ANALYSES OF THE PROTEOLYTIC PRODUCTSOFTHEINNERLAYEROFTHEMEDAKA 9AMAGAMI SPECULATES THAT SIX GLYCOPROTEINS RANGING IN MOLECULARWEIGHTFROMTOK$A WITHAREPEATING POLYPEPTIDEUNITOFABOUTK$A ARELINKEDTOFORM THE LAMELLAE WHILE THE INTERLAMELLAR PORTION MAY BE ANINTERLINKINGOF K$APROTEINS)NANOTHERSTUDY THECHORIONOFUNFERTILIZEDMEDAKAEGGSWASSHOWNTO CONSISTOFTWOMAJORPROTEINSOFTOANDK$A AS WELL AS A MINOR K$A PROTEIN )WAMATSU 3HI BATA AND+ANIE 5PONFERTILIZATION THEMAJOR PROTEINSAREPOLYMERIZEDTOINSOLUBLE HIGHMOLECULAR WEIGHTPROTEINSBYTHETEMPORARYFORMATIONOFSEVERAL NEWPROTEINS ANDK$A THEREBYIN CREASINGTOUGHNESSOFTHECHORION !NALYSISOFHOMOGENATESOFISOLATEDCHORIONSFROM MATUREOVARIANANDOVULATEDEGGSOF#ARASSIUSAURA TUSBY3$3 POLYACRYLAMIDEGELELECTROPHORESISSHOWS THEPRESENCEOFATLEASTBANDS#OTELLIETAL &IVEPRINCIPALCLASSESWERERECOGNIZED ! TO% INOR DEROFDECREASINGSIZES/FTHESE THE$ CLASS RANGING FROMTOK$A WASTHEMOSTPROMINENTANDREP RESENTEDABOUTOFTHETOTALCHORIONCOMPONENTS 4HEPRINCIPALGLYCOPROTEINSFOUNDINTHECHORIONSOF UNFERTILIZEDEGGSOFTHEWHITElSH#OREGONUSLAVARETUS HAVE A MOLECULAR MASS RANGING FROM TO K$A 3CAPIGLIATIETAL !NALYSISOFPURIlEDCHORION OF/NCORHYNCHUSMYKISSSHOWEDAPATTERNOFFOURMA JOR COMPONENTS AND K$ REPRESENT INGABOUTOFTHETOTALPROTEINS"RIVIO "ASSI AND #OTELLI 4HE AND K$ POLYPEPTIDES ARE GLYCOSYLATEDANDBELONGTOTHEhASPARGINE LINKEDGLY

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COPROTEINFAMILY4HIShSIMPLEvPATTERNOFTHECHORION OF/MYKISSMAYREmECTITSAPPARENTHOMOGENEITYAS OBSERVED WITH THE ELECTRON MICROSCOPE COMPARED TO OTHERSPECIES#OTELLIETAL 4HE SECONDARY ENVELOPE MAY PRODUCE FANTASTIC ORNAMENTATION /N THE PELAGIC EGGS OF THE # / SOLE 0LEURONICHTHYS COENOSUS IT FORMS ROUGHLY HEXAGONAL COMPARTMENTS ABOUT M ACROSS WITH WALLS ABOUT MHIGHANDTOMTHICK&IGURE 3TEHR AND (AWKES 4HE mOOR OF EACH COMPARTMENT IS PERFORATED BY REMNANTS OF THE PORE CANALS EACH PORE BEING SURROUNDED BY A SUBPATTERN OF POLYGONAL RIDGES)TISSUGGESTEDTHATTHISCOMPLEXCHORIONMAY INmUENCEBUOYANCYOFTHEEGGITMAYALSOSTRENGTHEN THEEGGSURFACEANDACTASARESILENTBUMPER0ERHAPS THEMOSTELABORATESECONDARYENVELOPEOFANYSPECIES SOFARDESCRIBEDISTHATOFTHEhANNUALvCYPRINODONTS #YNOLEBIAS MELANOTAENIA AND # LADIGESI WHERE THE EGGSMUSTSURVIVEINDAMPSOILDURING3OUTH!MERICAN DRYSEASONSWHENTHEIRAQUATICHABITATDRIES7OURMS 7OURMSAND3HELDON 4HESURFACEOFTHE EGG BRISTLES WITH UNIFORMLY SPACED HOLLOW CONICAL PROJECTIONS ABOUTMMLONG THATTERMINATEASA CROWNOFRECURVEDSPIKES&IGURE 4HISORNAMEN TATIONOFELABORATECHORIONICEXTENSIONSMAYFUNCTION AShGILLSvFORTHELONGPERIODSSPENTINDAMPSOIL4HEY MAY ALSO PROVIDE AN ANCHOR FOR PERIODS OF mOODING ANDBESHOCKABSORBERSTOPROTECTTHEEGGFROMSHARP PARTICLESINTHESOIL 3OMETIMESTHESECONDARYENVELOPEISCOATEDWITHA GELATINOUSMATERIALTHATPROBABLYCONTRIBUTESTOTHEAD HESIVENESSOFTHEEGG4HEDEMERSALEGGSOFTHEBLENNY "LENNIUSPAVOAREATTACHEDTOTHESUBSTRATUMBYANAD HESIVEDISCTHATCOVERSABOUTONE THIRDOFITSSURFACE 0ATZNER 4HISDISCCONSISTSOFATANGLEDMESH OF hANCHORING lLAMENTSv &IGURES ! " ATTACHED TOTHEREMAINDEROFTHECHORIONBYBRANCHINGROOT LIKE STRUCTURES4HEMICROPYLEISLOCATEDATANAKEDAREAAT THECENTREOFTHISADHESIVEDISC&IGURES% & PRE SUMABLYTHESPERMATOZOONMAKESITSENTRANCEBEFORE ATTACHMENTOFTHEEGG%LECTRONMICROGRAPHSOFCROSS SECTIONSOFTHESElLAMENTSSHOWAPATTERNOFSUBlLA MENTSSIMILARTOTHEhMICROTUBULEMIMICSvTHATCONSTI TUTETHElLAMENTSSEENIN&UNDULUS&IGURE$ 4HE THICKNESS AND COMPLEXITY OF THE CHORION OF lSHESSHOWWIDEVARIATION3TEHRAND(AWKES ,NNING +JRSVIK AND&ALK 0ETERSEN 'ENERAL LY CHORIONSOFMARINETELEOSTEGGSTHATAREPELAGICAND mOATFREEINOPENWATERARETHINWITHAHOMOGENEOUS LAMELLATED STRUCTURE &IGURE #HORIONS OF DE

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ENTLY OF lNE lBRILS THE CHORION PERSISTS DURING EM BRYOGENESIS 4HERE ARE TWO DISTINCTIVE SECONDARY ENVELOPES ON THESURFACEOFTHELAMPREYEGGAN !0)#!, 45&4ONTHE ANIMALPOLEANDANELABORATELYTEXTURED!$(%3)6%#/!4 THAT CUPS THE VEGETAL TWO THIRDS OF THE EGG &IGURES ! AND +ILLE 9ORKE AND -C-ILLAN 4HE APICAL TUFT CONSISTS OF TRANSPARENT NON STICKYGELATINOUSMATERIALTHATAPPEARSTOBESECRETED ANDMOULDEDBYACAPOFFOLLICULARCELLSINTHEAPICAL REGION UNDER PHASE CONTRAST OR POLARIZED LIGHT IT IS SEEN TO CONTAIN MANY lNE lBRILS &IGURES # AND ! 4HE ADHESIVE COAT IS AN UNUSUAL SECONDARY ENVELOPEINTHATITCONSISTSOFREMNANTSOFSPECIALIZED FOLLICULAR CELLS THE !$(%3)6% #%,,3 THAT BREAK DOWN DURINGOVULATION9ORKEAND-C-ILLAN $URING MATURATION THESE FOLLICULAR CELLS ENLARGE AND BECOMEPACKEDWITHHUGESACCULES&IGURE )N ADDITION THEIR CYTOPLASM CONTAINS ABUNDANT GRANULAR ENDOPLASMICRETICULUMANDMITOCHONDRIA'OLGICOM PLEXESANDAGRANULARENDOPLASMICRETICULUMARELIM ITED TO THE CYTOPLASM ADJACENT TO THE ZONA PELLUCIDA 4HE NUCLEUS IS LOCATED IN AN EXTREME BASAL POSITION TOWARD THE OVERLYING THECA AND THE ENTIRE SURFACE OF THE CELL IS COVERED WITH MICROVILLI WHICH ON ONE SIDEAREINCONTACTWITHTHEZONAPELLUCIDA4HESAC CULESAREFORMEDBYTHECOALESCENCEOFTWOTYPESOF MEMBRANE BOUND VESICLES THAT ARE PRODUCED BY THE 'OLGI COMPLEX AND GRANULAR ENDOPLASMIC RETICULUM RESPECTIVELY&IGURE "USSON -ABILLOT B $URING OVULATION THE ADHESIVE CELLS BREAK DOWN BEGINNING IN REGIONS ADJACENT TO THE ZONA PELLUCIDA &IGURES ! " 9ORKE AND -C-ILLAN 4HEINTRACELLULARSACCULESBECOMEATTACHEDTO THE ZONA PELLUCIDA FORMING THE ELABORATE ADHESIVE COAT &IGURE $ ! SIMILAR SORT OF ADHESIVE COAT IS DESCRIBED ON THE EGGS OF THE CLUPEID $OROSOMA PETENENSEWHERETHEFOLLICULARCELLSARERETAINEDONTHE SURFACEOFTHEZONAPELLUCIDAAFTEROVULATION3HELTON 4HIS EPITHELIUM IS SAID TO TRANSFORM DIRECTLY INTOAFUNCTIONAL STICKYEGGMEMBRANE ! BRIEF DESCRIPTION OF THE CHORION OF THE HAGlSH %PTATRETUSSTOUTIINDICATESASIMILARSORTOFCOMPLEX LAMELLARCHORIONINTHISDISTANTLYRELATEDSPECIES+OCH ET AL )T IS VARIABLE IN THICKNESS BUT ABOUT MTHICKINTHElGURESHOWN&IGURE )TCON SISTS OF THREE LAYERS AN OUTER COLUMNARGLOBULAR RE GION AMIDDLEREGIONOFTOHORIZONTALLAMELLAE ANDANINNERDENSELAYER

-ICROPYLE

4HETOUGHCHORIONOFTELEOSTEGGSISIMPENETRABLETO SPERMATOZOAANDTHEONLYPASSAGEWAYFORASPERMATO ZOONTOFERTILIZETHEEGGISBYWAYOFAPORETHATPEN ETRATESTHECHORIONATTHEANIMALPOLE THE -)#2/09,% 3INCE TELEOSTEAN SPERMATOZOA LACK ACROSOMES AND NEEDNOTDISSOLVETHEEGGMEMBRANETOREACHTHEEGG SURFACE THEY DO NOT REQUIRE CAPACITATION BEFORE THEY CANATTACHANDFUSEWITHTHEOOLEMMA)WAMATSU )SHI JIMA AND.AKASHIMA 4HElRSTSPERMATOZOON REACHESTHEMICROPYLEWITHINSECONDSOFINSEMINATION ANDENTERSTOINTERACTWITHMICROVILLIOFTHE 30%2- %. 4293)4%ONTHEOOLEMMA&IGURESAND /HTA AND)WAMATSU 7OLENSKIAND(ART A"ERN AND!VTALION 4HEMICROPYLE THEREFORE ORIENTS THEPOSITIONOFSPERMENTRYTOAREGIONONTHEANIMAL POLE NEAR THE EGG NUCLEUS 4HE SPEED OF SPERMATO ZOA OF THE MEDAKA /RYZIAS LATIPES DECREASES AS THEY MOVEDOWNTHEMICROPYLARCANALTOWARDTHEOOLEMMA &IGURE )WAMATSU )SHIJIMA AND .AKASHIMA )SHIJIMA (AMAGUCHI AND )WAMATSU &OLLOWINGATTACHMENTOFTHESPERMATOZOONTOTHEEGG MICROVILLI THESPERMHEADISRAPIDLYENGULFEDBYFU SIONOFTHEPLASMAMEMBRANESOFTHEINTERACTINGGAM ETES )MMEDIATELY AFTER THIS RAPID RESPONSE THE EGG PLASMAMEMBRANEELEVATESTOFORMTHENIPPLE SHAPED &%24),):!4)/. #/.% INTO WHICH THE ENTIRE SPERM HEAD MIDPIECE ANDAPORTIONOFTHEmAGELLUMAREABSORBED )N EGGS OF THE ZEBRA DANIO "RACHYDANIO RERIO THIS OCCURSBETWEENONEANDTWOMINUTESAFTERINSEMINA TION7OLENSKIAND(ART A 4HE MICROPYLAR AREAS OF SALMONID AND HERRING EGGS POSSESS SOME hSPERM GUIDANCE FACTORSv WHICH FACILITATE ENTRY OF HOMOLOGOUS SPERMATOZOA INTO THE MICROPYLE9ANAGIMACHIETAL !SUBSTANCEIN UNFERTILIZEDEGGSOFTHEMEDAKA/RYZIASLATIPESGUIDES SPERMATOZOAINTOTHEMICROPYLE)WAMATSU )SHIJIMA AND.AKASHIMA 4HISGUIDANCEFACTORMAYEXIST INTHEMICROPYLARAPPARATUSRATHERTHANINTHEPERIVI TELLINE SPACE OR CORTEX IT LOSES ITS ACTIVITY FOLLOWING FERTILIZATION 'LYCOPROTEINS OCCURRING IN A hDILUTED MUCUSAREAvINTHEOUTERMOSTLAYEROFTHECHORIONOF UNFERTILIZEDEGGSOFTHEMEDAKAPLAYANIMPORTANTROLE INGUIDINGSPERMATOZOAINTOTHEMICROPYLE)WAMATSU 9OSHIZAKI AND3HIBATA 4HEREDUCEDINCIDENCE OFSPERMENTRYINTOMICROPYLESOFFERTILIZEDEGGSSEEMS TO RESULT FROM INACTIVATION OF THESE GLYCOPROTEINS AS THEYARERENDEREDINSOLUBLEBYPOLYMERIZATIONFOLLOW INGFERTILIZATION

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)NTHEGRASSGOBY:OSTERISESSOROPHIOCEPHALUS FOL LICULARCELLSPRODUCEAFORESTOFATTACHMENTlLAMENTS UPTOMINLENGTHSURROUNDINGTHEMICROPYLE&IG URE 'IULIANINI AND &ERRERO 4HESE SPE CIALIZATIONS OF THE SECONDARY ENVELOPE FORM A CROWN ABOUTMINDIAMETERTHATWOULDAPPEARTOPRESENT ABARRIERTOSPERMENTRY'IULIANINIETAL 4HE SPERM HOWEVER AREABLETOPASSTHROUGHPERFORATIONS BETWEENTHElLAMENTINSERTIONSONTHECHORIONEVEN WHEN THE EGG ADHERES STRONGLY TO ITS SUBSTRATE TO REACHTHEMICROPYLE&IGURE 3CANNING ELECTRON MICROGRAPHS SHOW THAT ENTRY TO THE MICROPYLAR CANAL OF MANY SPECIES IS ATTAINED THROUGH A FUNNEL SHAPED 6%34)"5,% ON THE OUTER SUR FACE OF THE CHORION &IGURE 3ZÚLLÚSI AND "IL LARD 3TEHR AND (AWKES +OBAYASHI AND 9AMAMOTO )WAMATSU AND /HTA B /HTA AND)WAMATSU (ART 0IETRI AND$ONOVAN 7OLENSKI AND (ART A )WAMATSU )SHIJIMA AND .AKASHIMA )WAMATSU ET AL )N SOME SPECIES THE VESTIBULE IS SURROUNDED BY SMALL PORES ANDOR PROTRUSIONS THAT MAY PRODUCE PHEROMONES ATTRACTING SPERMATOZOA TO THE MICROPYLE 3TEHR AND (AWKES 3PERMATOZOAOFTHECYPRINIFORM"AR BUSCONCHONIUSANDTHEPERCIFORM,UCIOCEPHALUSSP MAYBEGUIDEDTOTHEMICROPYLEBYANELABORATEPAT TERN OF SPIRAL RIDGES THAT EMBOSS THE CHORION OF THE ANIMALPOLEONCESOMEFORMOFSPECIES SPECIlCCHE MOATTRACTANT BRINGS THEM CLOSE TO THE EGG &IGURES AND !MANZEAND)YENGAR 2IEHLAND +OKOSCHA )N&UNDULUSHETEROCLITUS WHEREl BRES OF THE SECONDARY ENVELOPE COULD IMPEDE ACCESS BYSPERMATOZOA AlBRIL FREEZONE TOMINDI AMETER SURROUNDSTHEMICROPYLE+UCHNOWAND3COTT /N THE CONTRARY THE PERIMICROPYLAR REGION OF SEVERALSPECIESOFCYPRINODONTSISSURROUNDEDBYAD HESIVElLAMENTSWHILETHERESTOFTHECHORIONEXHIBITS SIMPLEORNAMENTATIONSOFVARYINGSHAPE&IGURE 4HIAWAND-ATTEI 4HEWALLSOFTHEVESTIBULE IN &UNDULUS ARE STUDDED WITH SMALL TAPERED PROJEC TIONS&IGURE! $UMONTAND"RUMMETT IN "RACHYDANIO RERIO RADIAL FOLDS ADORN THE FUNNEL (ARTAND$ONOVAN %GGSOFTHELEAFlSH.AN DUS NANDUS .ANDIDAE 0ERCIFORMES ARE ATTACHED TO PLANTSANDOTHERSUBSTRATESBYADENSECARPETOFSHORT lLAMENTSARRAYEDINACIRCULARAREAAROUNDTHEMICRO PYLE&IGURE "RITZ 4HEMICROPYLEOFTHE BLENNY"LENNIUSPAVOISATTHECENTREOFANADHESIVE DISC THAT CONSISTS OF AN ELABORATE MESH OF ANCHORING lLAMENTSSECONDARYENVELOPE ATTACHEDTOTHECHORION

&IGURES% & 0ATZNER )TISACONUNDRUM HOWSPERMATOZOAPENETRATETHISJUNGLEOFlLAMENTSTO REACHTHEMICROPYLEOFANATTACHEDEGG 4HEWALLSOFTHEMICROPYLARCANALMAYBESCULPTED REmECTINGTHELAMINARSTRUCTUREOFTHECHORIONhGIVING THEAPPEARANCEOFLEAmETSOFANIRISDIAPHRAGMv&IGURE " !NNULARORSPIRALRIB LIKETHICKENINGSAREOFTEN OBSERVED WITHIN THE CHANNEL +OBAYASHI AND9AMA MOTO 0ATZNER .AKASHIMAAND)WAMATSU )N SEVERAL SPECIES THE MICROPYLAR OPENING AT THEBOTTOMOFTHEMICROPYLARCANALTERMINATESONTHE INNERSURFACEOFTHECHORIONASACRATERINTHECENTREOF ABULGETHATNESTLESSNUGLYAGAINSTTHEOOLEMMA3TEHR AND(AWKES +OBAYASHIAND9AMAMOTO /HTAAND)WAMATSU 9AMAMOTOAND+OBAYASHI )N&UNDULUSTHISOPENINGISTOMINDI AMETERANDISSURROUNDEDBYASMALL SMOOTHLIP$U MONTAND"RUMMETT $IFFERENCES IN THE APPEARANCE WITH THE SCANNING ELECTRONMICROSCOPE OFTHEMICROPYLEANDSURFACEPAT TERNSOFTHECHORIONKNOBS PITS ETC HAVEBEENUSED TO IDENTIFY THE EGGS OF SEVERAL SPECIES OF SALMONIDS ANDACLASSIlCATIONOFTHREECATEGORIESOFMICROPYLES HASBEENSUGGESTED2IEHL 490%)HASADEEPPIT ANDSHORTCANAL 490%))AmATPITANDLONGCANAL AND 490%)))ACANALBUTNOPIT4HESIDESOFTHECANALSARE OFTEN REINFORCED BY ANNULAR OR HELICOID THICKENINGS 4HE EGGS OF SALMONIDS STUDIED lT INTO CATEGORIES ))OR))))TISINTERESTINGTONOTE HOWEVER THATEGGSOF SOMESPECIESOF3ALMOARECLASSIlEDAS4YPE))SALAR ALPINUS ANDOTHERSAS4YPE)))GAIRDNERI TRUTTA .O PIT OR VESTIBULE IS SEEN IN THE 4YPE ))) MICROPYLE OF THEEEL!NGUILLAJAPONICA/HTAETAL !SPE CIES SPECIlCMICROPYLEMAYPRESENTTHEINITIALISOLAT ING MECHANISM IN SYMPATRIC SPECIATION ANDOR IS AN IMPORTANT FEATURE OF SPERM SELECTION 2IEHL (IRAI HASDISTINGUISHEDNINESPECIESOFPELAGIC EGGSBYMEANSOFASIMPLIlEDTECHNIQUEFORSCANNING ELECTRONMICROSCOPY ! TAXONOMIC KEY BASED ON CHARACTERISTICS OF THE MICROPYLEOFUNFERTILIZEDEGGS ASSEENWITHTHESCAN NINGELECTRONMICROSCOPE HASBEENPREPAREDFORFOUR SPECIES OF 3PARIDAE &IGURE #HEN 3HAO AND 9ANG #LADISTICANALYSESOFTHESTRUCTUREOFTHE MICROPYLESWEREUSEDTOSUGGESTGENERICINTERRELATION SHIPSBETWEENTHESPECIESTHERESULTSAGREEWITHCON CLUSIONS OBTAINED USING MORPHOLOGICAL BIOCHEMICAL ANDMOLECULARDATA4HISSTUDYWASEXTENDEDTOFOUR SPECIESINTHREEOTHERFAMILIESOF0ERCIFORMES,I 7U AND 9ANG ALTHOUGH THE ULTRASTRUCTURE OF THE

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SURFACEOFTHEZONAPELLUCIDA THEDENSITYOFDISTRIBU TIONOFPORES ANDTHESIZEOFTHEEGGSWEREUSEFULCHAR ACTERSFORDISTINGUISHINGTHESPECIES THEULTRASTRUCTURE OFTHEMICROPYLESWASTHEMOSTIMPORTANTFEATUREFOR IDENTIFYINGTHEEGGS-ICROPYLESINBOTHOFTHESESTUD IESWEREOF4YPE))) %LABORATE SURFACE ARRAYS OF PARALLEL RIDGES ON THE ZONA PELLUCIDA SUGGEST PHYLOGENETIC RELATIONSHIPS AMONG CERTAIN ANABANTOID GENERA "RITZ +OKOSCHA AND 2IEHL 4HESE RIDGES SPIRAL FROM THE4YPE )MICROPYLEANDAREPRESUMEDTOASSISTINSPERMGUID ANCE&IGURE 4HREEOFTHEGENERA #TENOPS 0ARA SPHAERICHTHYS AND 3PHAERICHTHYS ARE CONSIDERED TO BEMEMBERSOFTHEFAMILY"ELONTIIDAE!FOURTHGENUS ,UCIOCEPHALUS IS OFTEN GROUPED ALONE AS A SEPARATE SUBORDER ,UCIOCEPHALOIDEI.ELSON 3IMILARI TIES IN THE SPIRAL ARRAYS HAVE BEEN USED AS EVIDENCE FORINCLUSIONOFALLFOURGENERAINTHE!NABANTOIDEIOR PERHAPS INASEPARATESUBORDER 4HEOOLEMMABELOWTHEMICROPYLEISTHE30%2-%. 429 3)4%&IGURE "RUMMETTAND$UMONT (ARTAND$ONOVAN /HTAAND)WAMATSU 7OLENSKI AND (ART A /HTA 4HIS REGION OF THE EGG OF "RACHYDANIO CONFORMS TO THE SHAPE OF THEINNERSURFACEOFTHEMICROPYLE RESULTINGINADEEP DEPRESSION OF ITS SURFACE &IGURE ! 4HE PLAS MALEMMA OF THIS REGION DIFFERS FROM THE REST OF THE EGG SURFACE OFTEN DISPLAYING A DISTINCT CLUSTER OF TO MICROVILLI &IGURES " AND ! 4HE RE MAINDEROFTHEOOLEMMASURROUNDINGTHISAREAMAYBE CONTOUREDBYINTERCONNECTINGSMALLFOLDSORMICROPLI CAE 4HE lRST POLAR BODY OR A SCAR WHICH MARKS ITS FORMERPOSITION CANUSUALLYBEFOUNDABOUTM FROMTHECENTREOFTHESPERMENTRYSITEINTHEEGGSOF &UNDULUSHETEROCLITUS"RUMMETTAND$UMONT ! BAND OF COMPACT HOMOGENEOUS ELECTRON DENSE MATERIALSPREADSOUTFORSOMEDISTANCEINTHEOOPLASM BENEATHTHESPERMENTRYSITE&IGURE" /HTAAND )WAMATSU 7OLENSKIAND(ART A #ORTICAL GRANULESAREABSENTFROMTHECYTOPLASMINTHISREGION BUTMANYELONGATEMITOCHONDRIAANDANUMBEROFFREE RIBOSOMES HAVE BEEN DESCRIBED &IGURES ! " %LSEWHERE GRANULAR CORTICAL CYTOPLASM FORMS A UNI FORMLYTHICKBANDBELOWTHEOOLEMMA !LTHOUGH SPERM ENTRY SITES HAVE BEEN LESS EXTEN SIVELYSTUDIEDINNONTELEOSTEANlSH SEVERALINTERESTING EXAMPLES HAVE BEEN RECORDED IN !CIPENSERIFORMES )N!CIPENSERIDAE THENUMBEROFMICROPYLESVARIESIN DIFFERENTFEMALESOFASPECIESANDALSOINTHEEGGSOF ONE FEMALE ,INHART AND +UDO 4HE STURGEON

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&IGURE -ICROGRAPHS OF SECTIONS OF THE OVARY OF THE KILLIlSH &UNDULUS HETEROCLITUS &ROM "RUMMETT $UMONT AND ,ARKIN ¶REPRODUCEDWITHPERMISSIONOF*OHN7ILEY3ONS )NC ! 0HOTOMICROGRAPHOFAN%PONSECTIONTHROUGHTHEWALLANDOVIGEROUSLAMELLAOFANONGRAVIDOVARY-OSTFOLLICLESARECLOSELY APPOSEDTOTHELAYERDElNINGTHELUMEN, OFTHEOVARY!LOOSESTROMAlLLSTHESPACEBETWEENTHEFOLLICLESANDTHEOUTER MUSCULARTUNIC4 4HEARROWSINDICATEATRETICORDEGENERATINGPOSTOVULATORYFOLLICLES8 " 0HOTOMICROGRAPHOFAN%PONSECTIONTHROUGHTHEPRESUMEDSITEOFOVULATION4HELUMINALEPITHELIUM,% ISSTRETCHEDmAT ANDISCLOSELYAPPLIEDTOUNDERLYINGCONNECTIVETISSUEANDFOLLICULARELEMENTS/ OOCYTE6% ZONAPELLUCIDA4HEREISA YOUNGOOCYTEATEACHSIDEOFTHESITE8 # 4RANSMISSIONELECTRONMICROGRAPHOFASECTIONTHROUGHTHEFUTUREOVULATIONSITEANDSURROUNDINGLIP"LOODVESSELS"6 COURSEBENEATHTHEROUNDEDCELLSOFTHELIP,0 &LATTENEDLUMINALEPITHELIALCELLS,% OVERTHESITEAREUNDERLAINBYTHEIR BASALLAMINA VASCULARANDSTROMALELEMENTS3 THEFOLLICULARBASALLAMINA ANDTHEFOLLICULAREPITHELIUM&# 8 $ 4RANSMISSIONELECTRONMICROGRAPHOFASECTIONTHROUGHTHEFUTUREOVULATIONSITE4HEREHASBEENAPARTIALFUSIONOFTHEBASAL LAMINAE&", OFTHEmATTENEDLUMINALEPITHELIALCELLS,% ANDFOLLICULAREPITHELIUM&# 3OMESTROMALELEMENTS3 ARE VISIBLEINTHEINTERVENINGLAYER8

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&IGURE h&LUID OF OVULATIONv IN THE FOLLICLE OF THE LAMPREY 0ETROMYZON MARINUS &ROM9ORKE AND -C-ILLAN REPRODUCEDWITHPERMISSIONFROMTHE3OCIETYFORTHE3TUDYOF2EPRODUCTION )NC ! 0HOTOMICROGRAPHOFTHEAPICALAREAOFTHEFOLLICLEAFTERTHEFORMATIONOFTHEmUIDOFOVULATION& ATASITENEARTHEPOINTOF ENTRYOFABLOODVESSEL" 4HEZONAPELLUCIDA:0 ISENCLOSEDBYTHEFOLLICULARLAYERSARROW #ORDSOFYOLK FREECYTO PLASMWHITEARROW EXTENDFROMTHEECCENTRICNUCLEUS. TOTHESURFACEANDFORMTHEPOLARPLASM00 8 " 4RANSMISSIONELECTRONMICROGRAPHOFTHEAPICALREGIONOFAFOLLICLESHOWINGTHEFOLLICULARCELLSENCLOSINGTHEmUIDOFOVULA TION&/ SEVERALDAYSPRIORTOTHEEVENTSLEADINGTOTHERUPTUREOFTHEFOLLICLE4HEREISAGREATERACCUMULATIONOFLIPIDIN THISREGIONTHANINFOLLICULARCELLSELSEWHEREINTHEFOLLICLE !BBREVIATIONS" BLOODVESSEL)/ INTRAOVARIANSPACE,$ LIPID:0 ZONAPELLUCIDA9 YOLK

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&IGURE -ICROGRAPHSOFSECTIONSOFTHEFOLLICLEOFTHELAMPREY0ETROMYZONMARINUSDURINGOVULATION&OLLICULARCELLS CHANGESHAPE BEGINNINGATTHEmUID lLLEDENDOFTHEFOLLICLEASTHEYBECOMECOLUMNAR THEYFORMASLEEVE LIKECONSTRICTION THATGENTLYEXTRUDESTHEEGGFROMTHEFOLLICLE&ROM9ORKEAND-C-ILLAN REPRODUCEDWITHPERMISSIONFROMTHE3OCIETY FORTHE3TUDYOF2EPRODUCTION )NC ! 4RANSMISSIONELECTRONMICROGRAPH&OLLICULARCELLSINTHECONSTRICTEDAPICALREGIONOFTHEFOLLICLEAREMUCHTALLERTHANTHE ADJACENTFOLLICULARCELLSWHICHFORMASPHERECONTAININGlLAMENTOUSMATERIALANDTHEAMORPHOUSREMAINSOFTHEmUIDOF OVULATION4HETHECAISTHICKERANDMORECONVOLUTEDOVERTHECOLUMNARCELLS8 " 3CANNINGELECTRONMICROGRAPHOFTHEAPICALENDOFTHEFOLLICLEDURINGOVULATION4HEEGGISEXTRUDEDAHEADOFTHELENGTHEN INGCONSTRICTIONOFTHEFOLLICLE8 !BBREVIATIONS!& APICALFOLLICULARCELLS!- AMORPHOUSMATERIAL", BASALLAMINA#& COLUMNARFOLLICULARCELLS& APICAL ENDOFFOLLICLE&- lLAMENTOUSMATERIAL)/ INTRAOVARIANSPACE- MESOTHELIUM4 THECA

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&IGURE ,IGHTMICROGRAPHOFASECTIONOFANOVARIANFOLLICLEOFTHESEALAMPREY0ETROMYZONMARINUS!TRESIAISWELLAD VANCEDANDMUCHOFTHEOOCYTEHASBEENREMOVEDASARESULTOFEXTENSIVEPHAGOCYTICINVASION4HEZONAPELLUCIDAISCOLLAPSED BUTTHEFOLLICULARLAYERSREMAINDISTENDED0HAGOCYTESCANBESEENINSIDEANDOUTSIDETHEZONAPELLUCIDA8&ROM,EWIS AND-C-ILLAN ¶REPRODUCEDWITHPERMISSIONOF*OHN7ILEY3ONS )NC

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&IGURE -ICROGRAPHS OF SECTIONS THROUGH ATRETIC FOLLICLES OF THE PERCH 0ERCA mUVIATILIS!LL ARE ELECTRON MICROGRAPHS EXCEPTFOR$WHICHISAPHOTOMICROGRAPH&ROM,ANG BREPRODUCEDWITHPERMISSIONOFTHEAUTHOR ! %MPTY MEMBRANEBORDEREDVESICLES29/ REMAININTHEOOCYTEAFTERTHERESORPTIONOFPROTEINACEOUSYOLKPLATELETS9/ 4HEOOPLASMBETWEENTHESEREMNANTSISlLLEDWITHDEGENERATIVEMITOCHONDRIA8 " 4HECYTOPLASMOFAFOLLICULARCELLCONTAINSNUMEROUSCARBOHYDRATEVACUOLES6 WHOSECONTENTSAREBEINGRESORBEDLOWER ARROWHEAD ANDNUMEROUSSMOOTH SURFACEDVESICLESANDPINOCYTOTICELEMENTSUPPERARROWHEAD -0& BASALLAMINAOFTHE FOLLICULAREPITHELIUM8 # 4HECYTOPLASMOFAFOLLICULARCELLCONTAINSA'OLGICOMPLEX' GRANULARENDOPLASMICRETICULUM'%2 ANDCARBOHYDRATE VACUOLES6 !TEMPORARYGELATINOUSLAYER', FORMSBETWEENTHEZONAPELLUCIDAANDTHEFOLLICULARCELLS-0& BASAL LAMINAOFTHEFOLLICULAREPITHELIUM8

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&IGURE #ONTINUED $ 0HOTOMICROGRAPHOFTHEFOLLICULARENVELOPEOFANATRETICOOCYTE4HEFOLLICULARCELLSHAVEINVADEDTHEGELATINOUSLAYER', ANDCONTAINLARGEPOLYSACCHARIDEGRANULES2 ZONAPELLUCIDA8 % 3ECTIONOFTHEFOLLICULARENVELOPEOFANATRETICOOCYTE4HEGELATINOUSLAYER', HASBEENFRAGMENTEDINTOISLETSWHICH AREBEINGPHAGOCYTOSEDBYTHEFOLLICULARCELLS"OTHTHETHECAANDFOLLICULAREPITHELIUMCONTAINLEUCOCYTES, ANDWANDER INGCELLSWHICHDISCHARGETHEIRCONTENTSINTOTHEOVARIANLUMENARROW -0& BASALLAMINAOFTHEFOLLICULAREPITHELIUM8 & !TRETICOOCYTESHOWINGREMNANTSOFPROTEINACEOUSYOLKPLATELETS9/ WITHLYSOSOMES8

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&IGURE %LECTRONMICROGRAPHSOFSECTIONSTHROUGHATRETICFOLLICLESOFTHEELECTRICRAY4ORPEDOMARMORATA&ROM#HIEFl "ACCARIETAL REPRODUCEDWITHPERMISSIONFROM%LSEVIER3CIENCE ! )NTHISMICROGRAPH THEZONAPELLUCIDAHASDISAPPEAREDANDSEVERALFOLLICULARCELLSHAVEINVADEDTHEOOPLASM4HEFOLLICULAR CELLSAREPACKEDWITHYOLKPLATELETSANDTHEIRPLASMAMEMBRANESHAVEDEVELOPEDNUMEROUSUNDULATINGFOLDSF WHICHARE INDICATIVEOFTHEIRPHAGOCYTICACTIVITY-ITOCHONDRIAMI HAVEACCUMULATEDINTHEAPICALANDBASALREGIONS!FOLLICULARCELL ATTHEUPPERLEFTISPACKEDWITHLIPIDDROPLETS, ANDMYELINlGURESMB THELIPIDDROPLETSARESURROUNDEDBYROSETTESOF GLYCOGEN-EMBRANOUSENVELOPESME REMAININGFROMPHAGOCYTOSEDYOLKPLATELETS ARESCATTEREDTHROUGHOUTTHEFOLLICULAR CAVITY8 " !FOLLICULARCELLISPACKEDWITHPHAGOCYTOSEDYOLKPLATELETSY ENCLOSEDBYCONCENTRICMEMBRANOUSLAMELLAEMI MITO CHONDRIA8 # ,ARGEYOLKPLATELETSAREUNDERGOINGDIGESTION8 $ !lNALSTAGEINTHEDIGESTIONOFAYOLKDROPLET4HELIPID, ANDCARBOHYDRATECOMPONENTSGLYCOGENROSETTES G HAVE BECOMESEGREGATED8

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&IGURE %LECTRON MICROGRAPH OF A SECTION OF AN ATRETIC FOLLICLE IN THE OVARY OF THE HAGlSH %PTATRETUS STOUTI 4HECAL CELLS CONTAIN LYSOSOMES COLLOID DROPLETS GRANULAR ENDOPLASMIC RETICULUM 'OLGI COMPLEX AND MITOCHONDRIA 8 &ROM4SUNEKIAND'ORBMAN REPRODUCEDWITHKINDPERMISSIONOF"LACKWELL0UBLISHING !BBREVIATIONS#4 CONNECTIVETISSUE%# ENDOTHELIALCELL

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&IGURE -ICROGRAPHSOFSECTIONSOFPOSTOVULATORYFOLLICLESOFTHETELEOST!STYANAXBIMACULATUSLACUSTRISILLUSTRATINGPRO GRAMMEDCELLDEATHORAPOPTOSIS&ROM$RUMMONDETAL ¶REPRODUCEDWITHPERMISSIONOF*OHN7ILEY3ONS )NC ! 0HOTOMICROGRAPH OF A SECTION TAKEN A FEW HOURS AFTER SPAWNING THE FOLLICULAR CELLS & HAVE UNDERGONE HYPERTROPHY 4HEARROWINDICATESAMICROPYLARCELL8

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&IGURE %LECTRONMICROGRAPHOFASECTIONOFAPOSTOVULATORYFOLLICLEOFTHEPERCH0ERCAmUVIATILISSHOWINGTWOTYPESOF FOLLICULARCELLSONEHOURAFTEROVULATION4HELOWERCELLISPHAGOCYTICANDCONTAINSLYSOSOMES4HEUPPER LIGHTERCELLCONTAINS MITOCHONDRIAANDAGRANULARENDOPLASMICRETICULUM-0& FOLLICULARBASEMENTMEMBRANE8 &ROM,ANG AREPRO DUCEDWITHPERMISSIONFROM%LSEVIER3CIENCE

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&IGURE %LECTRONMICROGRAPHSOFSECTIONSOFPOSTOVULATORYFOLLICLESOFTILAPIA/REOCHROMISMOSSAMBICUSONEDAYAFTER SPAWNING&ROM3MITHAND(ALEY REPRODUCEDWITHPERMISSIONOFTHEAUTHORS ! -ITOCHONDRIA- WITHTUBULARCRISTAEINACELLOFTHETHECAINTERNA, LIPIDDROPLET8 " &OLLICULARCELLWITHBASALGRANULARENDOPLASMICRETICULUM2%2 ANDSUBAPICALAGRANULARENDOPLASMICRETICULUM3%2 2"# AREDBLOODCELLINTHEFOLLICULARLUMEN8 # #OLLAGENOUSlBRES# COURSEBETWEENTHETHECAINTERNA4) ANDTHEFOLLICULARBASALLAMINA"- 4HEFOLLICULARCELLS' CONTAINAGRANULARENDOPLASMICRETICULUM$ DESMOSOMES- MITOCHONDRIAWITHLAMELLARCRISTAE6 VESICLE8

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&IGURE %LECTRONMICROGRAPHSOFASECTIONOFAFOLLICULARCELLFROMAPOSTOVULATORYFOLLICLEOFTILAPIA/REOCHROMISMOS SAMBICUSSIXDAYSAFTERSPAWNING4HECELLCONTAINSBASALGRANULARENDOPLASMICRETICULUM2%2 TUBULARAGRANULARENDOPLAS MICRETICULUM3%2 ANDTHREE'OLGICOMPLEXES'/ NEARTHENUCLEUS. - MITOCHONDRIONWITHTUBULARCRISTAE8 4HE INSET SHOWS MICROVILLI -6 AND VESICLES AT THE APICAL PLASMA MEMBRANE 8 &ROM 3MITH AND (ALEY REPRODUCEDWITHPERMISSIONOFTHEAUTHORS

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&IGURE 4RANSMISSION ELECTRON MICROGRAPHS OF SECTIONS FROM POSTOVULATORY FOLLICLES OF MATURE COHO /NCORHYNCHUS KISUTCH&ROM.AGAHAMA #LARKE AND(OAR REPRODUCEDWITHPERMISSIONOFTHE.2#0RESS ! 3PECIALTHECALCELLS3# FORMACLUSTERCLOSETOTHESEROSALEPITHELIUM8 " $EGENERATEFOLLICULARCELLS"- FOLLICULARBASALLAMINA, LYSOSOME8 # 3PECIAL THECAL CELL SHOWING EXTENSIVE AGRANULAR ENDOPLASMIC RETICULUM AND LARGE MITOCHONDRIA WITH TUBULAR CRISTAE ' 'OLGICOMPLEX R%2 GRANULARENDOPLASMICRETICULUM8 $ 0ORTION OF A SPECIAL THECAL CELL CONTAINING EXTENSIVE AGRANULAR ENDOPLASMIC RETICULUM S%2 AND A LIPID DROPLET ,$ 8

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&IGURE 0ATHWAYOFSTEROIDBIOSYNTHESISINTHEOVARYOFSALMONIDS` (3$` HYDROXYSTEROIDDEHYDROGENASE ` (3$ ` HYDROXYSTEROID DEHYDROGENASE &ROM .AGAHAMA REPRODUCED WITH PERMISSION FROM THE :OOLOGICAL 3OCIETYOF*APAN

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&IGURE ! DIAGRAM TO ILLUSTRATE THE RECEPTOR ADENYLATE CYCLASE CYCLIC!-0 MECHANISM FOR ACTIVATION OF A FOLLICULAR GRANULOSA CELLINTHEAMAGOSALMONBY` (3$` HYDROXYSTEROIDDEHYDROGENASE &ROM.AGAHAMA REPRODUCED WITHPERMISSIONOFTHEAUTHOR

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&IGURE 3TEROIDOGENICPATHWAYSOFOVARIANOESTRADIOL ÀNDBIOSYNTHESISOF_ ` DIHYDROXY PREGNEN ONEIN OVARIANFOLLICLESOFTHEMEDAKADURINGVITELLOGENESISANDOOCYTEMATURATION&ROM+OBAYASHIETAL REPRODUCEDWITH PERMISSIONFROMTHE:OOLOGICAL3OCIETYOF*APAN

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&IGURE %LECTRONMICROGRAPHOFASECTIONTHROUGHTHEFOLLICULARWALLFROMTHEOVARYOFTHELAMPREY0ETEROMYZONMA RINUS4HESECTIONINCLUDESTHEZONAPELLUCIDA: ATTHERIGHT FOLLICULARCELLS& THECAINTERNA) THECAEXTERNA% ANDTHE COELOMICEPITHELIUM# ,ARGELIPIDDROPLETS, DISTENDACELLOFTHETHECAINTERNA8 &ROM7EISBART 9OUSON AND 7IEBE REPRODUCEDWITHPERMISSIONFROM%LSEVIER3CIENCE

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&IGURE %LECTRONMICROGRAPHSOFTHECHORIONOFTHEEGGOF"RACHYDANIORERIO&ROM(ARTAND$ONOVAN ¶REPRO DUCEDWITHPERMISSIONOF*OHN7ILEY3ONS )NC ! 4RANSMISSIONELECTRONMICROGRAPHOFASECTIONTHROUGHTHECHORIONOFANUNFERTILIZEDEGGSHOWINGTHEOUTER ELECTRON DENSE ZONE: MIDDLElBRILLARZONE: ANDINNERLAMELLARZONE: 4HESURFACEOFTHECHORIONISCOVEREDBYATHINLAYEROF GRANULARMATERIALANDDOME SHAPEDELECTRON DENSEBODIES0 PORECANAL8 " 4RANSMISSIONELECTRONMICROGRAPHOFASECTIONTHROUGHAPORECANAL0 WITHITSPOREPLUG00 INTHEOUTER ELECTRON DENSE ZONE: 4HElBRESOFTHEMIDDLELAYERAREARRANGEDINCRISSCROSSINGBUNDLESAROUNDTHEOUTERPORTIONOFTHEPORECANAL 8 # 3CANNINGELECTRONMICROGRAPHOFTHEOUTERSURFACEOFTHECHORIONSHOWINGHEMISPHERICAL DOME LIKEPROJECTIONS8

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&IGURE -ICROGRAPHSOFSPERMENTRYSITESONEGGSOFTHEZEBRAlSH"RACHYDANIORERIO&ROM7OLENSKIAND(ART A ¶REPRODUCEDWITHPERMISSIONOF*OHN7ILEY3ONS )NC ! 0HOTOMICROGRAPHOFASECTIONTHROUGHTHEMICROPYLARREGIONOFANUNACTIVATEDEGG4HEMICROPYLE CONSISTINGOFTHEOUTER VESTIBULE V AND THE INNER MICROPYLAR CANAL C PRODUCES A CONE SHAPED DEPRESSION IN THE EGG SURFACE! SINGLE LAYER OFSMALLCORTICALGRANULESCG LIESBENEATHTHEOOLEMMAEXCEPTINTHEREGIONOFTHEINNERMICROPYLARAPERTUREARROW 8 " 4RANSMISSIONELECTRONMICROGRAPHOFASECTIONTHROUGHTHESPERMENTRYSITESHOWINGMICROVILLIPROJECTINGTHROUGHTHEINNER MICROPYLARAPERTUREINTOTHEMICROPYLARCANALC !NELECTRON DENSELAYERARROWS BENEATHTHESPERMENTRYSITESPREADS OUTWARDFORSOMEDISTANCEBELOWTHEOOLEMMA8 # 3CANNINGELECTRONMICROGRAPHOFACROSSFRACTURETHROUGHTHEMICROPYLElVESECONDSAFTERINSEMINATION4HEINNERMICRO PYLARAPERTUREARROWS ACCOMMODATESASINGLESPERMATOZOON8 $ 3CANNINGELECTRONMICROGRAPHOFAFERTILIZINGSPERMATTACHEDTOTHEMICROVILLIOFTHESPERMENTRYSITElVESECONDSAFTER INSEMINATION"INDINGOCCURSARROW BETWEENTHEMICROVILLIANDTHEEQUATORIALSURFACEOFTHESPHERICALSPERMHEADH 8

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&IGURE $IAGRAMOFTHESTRUCTUREOFTHEMICROPYLEOFTHEMEDAKA/RYZIASLATIPES4HESPEEDOFASWIMMINGSPERMATO ZOONDECREASESASITMOVESDOWNTHEMICROPYLARCANALTOWARDTHEOOLEMMA4HEINNERDIAMETER)$ ATTHEVESTIBULEM THEOUTERAPERTUREM ANDTHEENDOFTHECANALM AREINDICATED4HEINNERWALLOFTHEMICROPYLECONSISTSOFTHE OUTERMOSTLAYER/, OFTHECHORIONINTHEOUTERTWOTHIRDS INCLUDINGTHEVESTIBULE6" ANDTHEINNERLAYERSOFTHECHORIONIN THEINNERONETHIRDARROW OFTHEMICROPYLE&ROM)WAMATSU )SHIJIMA AND.AKASHIMA ¶REPRODUCEDWITHPERMISSION OF*OHN7ILEY3ONS )NC

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&IGURE 3CANNINGELECTRONMICROGRAPHSOFTHEMICROPYLARAREAOFMATUREEGGSOFTHEGRASSGOBY:OSTERISESSOROPHIO CEPHALUS&ROM'IULIANINIAND&ERRERO REPRODUCEDWITHPERMISSIONFROM5NIONE:OOLOGICA)TALIANA ! !FORESTOFATTACHMENTlLAMENTSUPTOMINLENGTHFORMSACROWNABOUTMINDIAMETERAROUNDTHEMICROPYLE "ARM " 4HEMICROPYLARPITISSURROUNDEDBYPERFORATIONSASTERISKS FORMEDBYMERGEDBASALlLAMENTS"ARM # ,ATERAL VIEW OF THE OOCYTE SHOWING A CRIBIFORM COLUMN OF NETTED lLAMENTS RISING FROM THE BASAL PLATE SURROUNDING THE MICROPYLARAREA4HElLAMENTSDIVIDEANDFRAYDISTALLY"ARM !BBREVIATIONSES EGGSURFACEF lLAMENTSFP lLAMENTPLATEM MICROPYLEPC PORECANAL

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&IGURE %NTRY INTO THE MICROPYLAR CANAL OF MANY SPECIES IS ATTAINED THROUGH A FUNNEL SHAPED VESTIBULE ON THE OUTER SURFACEOFTHECHORION&ROM)WAMATSUETAL REPRODUCEDWITHPERMISSIONFROMTHE:OOLOGICAL3OCIETYOF*APAN ! " 3CANNING ELECTRON MICROGRAPHS OF THE MICROPYLES FROM EGGS OF MEDAKA /RYZIAS LATIPES ! AND / MELASTIGMA " ,ONGITUDINALSECTIONSTHROUGHTHEMICROPYLESARESHOWNINTHEDIAGRAMSBELOW6" VESTIBULE"ARSM # $0HOTOMICROGRAPHSOFUNFERTILIZEDEGGSOF/LATIPESSHOWINGAMICROPYLEWITHALARGEVESTIBULE# ANDONEWITHASMALL VESTIBULE$ "ARSM

@±± &IGURE 3CANNING ELECTRON MICROGRAPHS OF ARTIlCIALLY FERTILIZED EGGS OF THE GRASS GOBY :OSTERISESSOR OPHIOCEPHALUS &ROM'IULIANINIETAL REPRODUCEDWITHPERMISSIONFROM%LSEVIER3CIENCE ! 3IDEVIEWOFlLAMENTADHESIONAPPARATUSF WITHBASALPERFORATIONSP ADJACENTTOTHEEGGSURFACEE "ARM " "ASAL PLATE VIEWED FROM THE INNER MICROPYLAR FACE WITH HEADS OF SPERMATOZOA H INSIDE THE ADHESION APPARATUS "ARM # "ASALlLAMENTSFRACTUREDTOSHOWTAPEREDPERFORATIONS4HEARROWSINDICATETHEMINIMUMWIDTH"ARM $ 0ERFORATIONSP VIEWEDFROMTHEOUTERSIDESHOWINGRHOMBOIDBOTTLENECK"ARM % 3PERMATOZOONH ENTERINGAPERFORATIONFROMTHEOUTERSIDE.OTETHEmAGELLUMm OFASPERMATOZOONTHATHASJUSTENTERED "ARM

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&IGURE 3CANNINGELECTRONMICROGRAPHSOFTHEEGGOFTHEPERCIFORM,UCIOCEPHALUSSPTOSHOWANELABORATEPATTERNOF SPIRALRIDGESSURROUNDINGTHEMICROPYLARPITINDICATEDBYANARROWINEACHMICROGRAPH &ROM2IEHLAND+OKOSCHA REPRODUCEDWITHPERMISSIONFROM%LSEVIER3CIENCE ! 6IEWOFTHEENTIREEGG"ARM " 3OMEOFTHESPIRALRIDGESENTERTHEMICROPYLARPIT"ARM # 4HEMICROPYLECONSISTSOFTHEMICROPYLARPITARROW ANDTHEMICROPYLARCANALATTHECENTRE"ARM $ 4HEMICROPYLARCANALARROW ISATTHECENTREOFTHEMICROPYLARPIT-0 "ARM

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&IGURE 3CANNING ELECTRON MICROGRAPHS OF THE EGG OF TWO CYPRINODONTS 4HE MICROPYLAR REGION IS SURROUNDED BY ADHESIVElLAMENTSWHILETHERESTOFTHECHORIONEXHIBITSSIMPLEORNAMENTATIONSOFVARYINGSHAPE&ROM4HIAWAND-ATTEI REPRODUCEDWITHPERMISSIONOFTHE.2#0RESS ! &UNDULUSOMA THIERRYI 4HE MICROPYLE OPENS THROUGH A VESTIBULE ARROW 4HERE ARE MANY lLAMENTS IN THE REGION OF THEMICROPYLE& BUTSOMEAREIMPLANTEDINOTHERREGIONS& "ARM " 4HEMICROPYLARAPPARATUSOFTHEEGGSHOWNIN!4HEMICROPYLARCANALISBLOCKEDBYAPLUGARROW 3OMElLAMENTS& ARE IMPLANTEDINTHEVESTIBULE6 "ARM # %PIPLATYSFASCIOLATUS4HESURFACEOFTHEEGGISORNAMENTED/ lLAMENTSARECONCENTRATEDINAREGIONWITHOUTORNAMENTA TION4HEDOUBLEARROWINDICATESAlLAMENTTHATISIMPLANTEDINTHEMEDIANREGIONOFTHEEGG"ARM $ %NLARGEMENT OF THE MICROPYLAR REGION OF THE EGG SHOWN IN # /RNAMENTATIONS O VISIBLE ON THE LEFT ARE ABSENT IN THEMICROPYLARREGION-2 "ARM

&IGURE 3CANNINGELECTRONMICROGRAPHSOFTHEMICROPYLARREGIONOFTHEEGGOF&UNDULUSHETEROCLITUS&ROM$UMONT AND"RUMMETT REPRODUCEDWITHPERMISSIONOF7ILEY ,ISS )NC ASUBSIDIARYOF*OHN7ILEY3ONS )NC ! 4HEMICROPYLE- ISSITUATEDATTHEBASEOFACONICALDEPRESSION4HEWALLSOFTHEDEPRESSIONAREADORNEDWITHSMALL TAPERED lLAMENTS3URROUNDING THE MICROPYLAR DEPRESSIONARESEVERALSHORTANDAFEWLONGARROW CHORIONIClLAMENTS 8 " 4HEMICROPYLEISSURROUNDEDBYARAISEDLIP4HEWALLSOFTHEMICROPYLARCANALAPPEARLIKEASERIESOFIRISDIAPHRAGMSREmECT INGTHELAMINARNATUREOFTHECHORION8

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&IGURE 3CANNINGELECTRONMICROGRAPHSOFAFRESHLYSPAWNEDEGGOFTHELEAFlSH.ANDUSNANDUS4HESEEGGSAREATTACHED TOVARIOUSSUBSTRATESBYADENSECARPETOFSHORTlLAMENTSARRAYEDAROUNDTHEMICROPYLE"RITZ COURTESYOFTHE!MERICAN -USEUMOF.ATURAL(ISTORY ! %GGATTACHEDTOMOSS"ARM " !NIMALPOLE"ARM # -ICROPYLARREGION"ARM $ -ICROPYLE"ARM

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&IGURE 4HESESCANNINGELECTRONMICROGRAPHSOFTHEMICROPYLESOFUNFERTILIZEDEGGSOFFOURSPECIESOF3PARIDAEWERE USEDASTHEBASISOFATAXONOMICKEYAO ACCESSORYOPENINGS"ARM&ROM#HEN 3HAO AND9ANG REPRODUCEDWITH PERMISSIONFROM%LSEVIER3CIENCE ! 3PARUSSARBA8 " !CANTHOPAGRUSLATUS8 # !SCHLEGELI8 $ 0AGRUSMAJOR8

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&IGURE 3CANNING ELECTRON MICROGRAPHS OF THE EGG OF ,UCIOCEPHALUS PULCHER %LABORATE ARRAYS OF PARALLEL RIDGES ON THE ZONA PELLUCIDA SUGGEST PHYLOGENETIC RELATIONSHIPS4HESE RIDGES SPIRAL FROM THE4YPE ) MICROPYLE AND ARE PRESUMED TO ASSIST IN SPERM GUIDANCE &ROM "RITZ +OKOSCHA AND 2IEHL REPRODUCED WITH PERMISSION FROM THE )CHTHYOLOGICAL 3OCIETYOF*APAN ! 6IEWOFTHEANIMALPOLEOFTHEEGG4HEARROWINDICATESTHEMICROPYLE8 " !NIRREGULARPATTERNOFRIDGESNEARTHEVEGETALPOLE8 # 4HEMICROPYLEARROW ATTHECENTREOFTHESPIRALINGRIDGESATTHEANIMALPOLE8 $ -ICROPYLARPITWITHTHEMICROPYLARCANALARROW 8

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&IGURE 3CANNING ELECTRON MICROGRAPHS OF THE MICROPYLAR REGION OF EGGS OF THE ROSE BITTERLING 2HODEUS OCELLATUS 8 &ROM/HTA REPRODUCEDWITHPERMISSION ! 3PERM ENTRYSITE33 OFANUNFERTILIZEDEGG#( CHORION " !FERTILIZINGSPERMATOZOONAPPEARSTOATTACHTOTHEMICROVILLIOFTHESPERM ENTRYSITE

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&IGURE 3CANNINGELECTRONMICROGRAPHSOFMATUREEGGSOFTHEPADDLElSH0OLYODONSPATHULA ANEGGWITHMULTIPLEMI CROPYLES&ROM,INHARTAND+UDO REPRODUCEDWITHPERMISSIONFROM%LSEVIER3CIENCE ! !GROUPOFMICROPYLESATTHEANIMALPOLE4HEEXTERNALAPERTURESARELINEDWITHCYLINDRICALSTRUCTURESFORMEDBYDIFFER ENTIATIONOFTHEOUTERMOSTLAYEROFTHECHORION8 " 4HEBROKENSURFACEOFTHECHORIONSHOWINGTHREELAYERS AND 4HEOUTERMOSTLAYERDIFFERENTIATESTOFORMCYLINDRICAL STRUCTURES8 # 4HESURFACEOFANEGGINTHEMICROPYLARREGIONWITHTHECHORIONREMOVED4HEROUNDIMPRESSIONOFTHElRSTPOLARBODY ARROW ISLOCATEDNEARAGROUPOFSPERMENTRYSITESARROWHEADS 8 )NSETTUFTOFMICROVILLIOFASPERMENTRYSITEONTHESURFACEOFTHEOOLEMMAUNDERAMICROPYLE8

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&IGURE 3CANNINGELECTRONMICROGRAPHOFTHEMICROPYLARREGIONOFAFERTILIZEDEGGOFTHEACTINOPTERYGIANlSH0OLYPTERUS ORNATIPINNIS4HECHORIONICSURFACEISCOVEREDWITHGLUTINOUSTUFTSEXCEPTFORASMALLAREAATTHEANIMALPOLE!NARROWRING LIKE WALLSURROUNDSTHEMICROPYLARAREAWITHTHEMICROPYLARCANALATTHECENTRE!NUMBEROFRIDGES ORIGINATINGFROMTHECIRCULAR WALL TRANSFORMCENTRIFUGALLYINTOTHEGLUTINOUSTUFTS&ROM"ARTSCHAND"RITZ REPRODUCEDWITHPERMISSIONOFTHE#AM BRIDGE5NIVERSITY0RESS

&IGURE 0HOTOMICROGRAPH OF A SECTION THROUGH A VITELLOGENIC OOCYTE OF THE WHITE BASS -ORONE CHRYSOPS SHOWING THE ZONA PELLUCIDA Z AT THE SITE WHERE THE MICROPYLAR CELL MC PENETRATES THE MICROPYLE 4HE CYTOPLASM CY BENEATH IS RELATIVELYFREEOFYOLKGLOBULES"ARM&ROM-YLONASETAL REPRODUCEDWITHPERMISSIONFROM%LSEVIER3CIENCE

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&IGURE 4HE MICROPYLE OF THE MEDAKA /RYZIAS LATIPES IS FORMED DURING VITELLOGENESIS BY A SINGLE MICROPYLAR CELL )TMOULDSTHEMICROPYLARCHANNELASTHEZONAPELLUCIDAISLAIDDOWNAROUNDIT&ROM)WAMATSU .AKASHIMA AND/NITAKE ¶REPRODUCEDWITHPERMISSIONOF*OHN7ILEY3ONS )NC ! 4RANSMISSION ELECTRON MICROGRAPH OF A SECTION THROUGH THE CYTOPLASMIC EXTENSION OF THE MICROPYLAR CELL -# AND MI CROPYLEOFAFULLY GROWNOOCYTE4HEOUTERLAYEROFTHECHORION/, EXTENDSINWARD OVERTHEINNERLAYER), TOLINE THE MICROPYLAR CANAL AS FAR AS THE LARGE ARROW 4HE CYTOPLASMIC EXTENSION CONTAINS A BUNDLE OF MICROTUBULES &OLDS IN THESURFACEOFTHECYTOPLASMICEXTENSIONMOULDINDENTATIONSINTHEWALLOFTHEMICROPYLARCANAL4HEMICROPYLARCELLIS ATTACHEDTOTHEINDENTEDOOLEMMABYTIGHTJUNCTIONSARROWHEADS /# OOCYTE8 " 4RANSMISSION ELECTRON MICROGRAPH OF A LONGITUDINAL SECTION OF THE MICROPYLE OF A MATURE EGG4HE OUTER LAYER /, OF THE CHORION IS ELECTRON DENSE AND OVERLIES THE INNER LAYER ), AROUND THE OUTER TWO THIRDS OF THE MICROPYLAR CANAL 8

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&IGURE #ONTINUED # 3CANNINGELECTRONMICROGRAPHSOFNON ATTACHINGlLAMENTSANDMICROPYLESATTHEANIMALPOLEMIDDLE BOTTOM ANDATTACH INGlLAMENTSATTHEVEGETALPOLETOP "ARM 4HETHREEPICTURESONTHELEFTAREFROMANEGGWITHALEFT HANDEDSPIRALARRAGEMENTOFTHEATTACHINGlLAMENTSANDNON ATTACHING lLAMENTS"OTTOMTHESPIRALINTHEWALLOFTHEMICROPYLEISLEFT HANDED 4HETHREEPICTURESONTHERIGHTAREFROMANEGGWITHARIGHT HANDEDSPIRALARRANGEMENTOFTHEATTACHINGlLAMENTSANDNON AT TACHINGlLAMENTS"OTTOMTHESPIRALINTHEWALLOFTHEMICROPYLEISLEFT HANDED

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&IGURE #ONTINUED $ 3CHEMATICDIAGRAMSHOWINGTWOPATTERNSOFATTACHINGANDNON ATTACHINGlLAMENTSANDMICROPYLESININTRAFOLLICULAROOCYTES OFTHEMEDAKA4HETHECALCELLLAYER4 ANDBASEMENTMEMBRANE"- AREIMMOBILE4HEMICROPYLARCELL-# ROTATES IN A RIGHT HANDED DIRECTION /N THE LEFT THE OOCYTE / WITH ITS FOLLICULAR LAYER ' MOVES IN A RIGHT HANDED DIRECTION ONTHERIGHT ITROTATESINALEFT HANDEDDIRECTION

&IGURE 4RANSMISSIONELECTRONMICROGRAPHOFTHEFOLLICULARLAYERINTHEANIMALPOLEREGIONOFANOOCYTEOFTHEMEDAKA /RYZIASLATIPES!MICROPYLARCELLMC WITHELECTRON DENSECYTOPLASMANDNUCLEOPLASMISSURROUNDEDBYFOLLICULARCELLGC ANDABUTSTHEZONAPELLUCIDACH 8 &ROM.AKASHIMAAND)WAMATSU ¶REPRODUCEDWITHPERMISSIONOF*OHN7ILEY 3ONS )NC )NSETPHOTOMICROGRAPHOFTHEWHOLEFOLLICLE8 !BBREVIATIONSB FOLLICULARBASALLAMINAO OOPLASMTC THECALCELLV SHORTVILLIPENETRATINGTHEZONAPELLUCIDA

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&IGURE $IAGRAMOFAMICROPYLARCELLFROMTHECHUMSALMON/NCORHYNCHUSKETADURINGVITELLOGENESIS4HEMAINCELL BODYISABOUTMHIGHANDMWIDEANDlTSINTOTHEMICROPYLARVESTIBULE)TSINNERSURFACEBEARSAFEWSHORTMICROVILLI WHEREASTHEOUTERSURFACE ABUTTINGPOLYGONALFOLLICULARCELLS ISSMOOTH4HECENTRALNUCLEUSCONTAINSlNELYDISPERSEDCHRO MATINANDAPROMINENTNUCLEOLUS'RANULARENDOPLASMICRETICULUMANDOTHERORGANELLESOCCUPYTHECYTOPLASMOFTHEMAINCELL BODY4HETHICKCYTOPLASMICPROCESSEXTENDSTHROUGHTHEMICROPYLARCANALABUNDLEOFMICROTUBULESFORMSITSCENTRALCORE 4HEBULBOUSENDOFTHEPROCESSINDENTSTHESURFACEOFTHEOOCYTE FORMINGDESMOSOMALJUNCTIONSWITHTHEOOLEMMA&ROM +OBAYASHIAND9AMAMOTO ¶REPRODUCEDWITHPERMISSIONOF*OHN7ILEY3ONS )NC

&IGURE 4RANSMISSIONELECTRONMICROGRAPHSOFSECTIONSOFMICROPYLARCELLSOFTHEMEDAKA/RYZIASLATIPES&ROM.A KASHIMAAND)WAMATSU ¶REPRODUCEDWITHPERMISSIONOF*OHN7ILEY3ONS )NC ! -ICROPYLARCELLDURINGEARLYVITELLOGENESIS4HECELLISLARGEWITHAmATTENEDNUCLEUS#YTOPLASMICORGANELLESAREABUNDANT 'OLGICOMPLEXESAREWELLDEVELOPEDONTHEOOCYTESIDEOFTHECELLBUNDLESOFTONOlLAMENTSAREAPPARENTONTHEOPPOSITE SIDE8 )NSET0HOTOMICROGRAPHOFTHEENTIREFOLLICLE8

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&IGURE #ONTINUED " ,ATER IN VITELLOGENESIS THE MICROPYLAR CELL HAS ASSUMED A MUSHROOM SHAPE AND ITS CYTOPLASMIC PROCESS HAS PENETRATED THEZONAPELLUCIDA!RROWHEADSINDICATESTRUCTURALDISTORTIONOFTHEINNERLAYEROFTHEZONAPELLUCIDA8 )NSET4HERECTANGLEONTHEPROCESSHASBEENENLARGEDTOSHOWABUNDLEOFMICROTUBULESBUTNOTONOlLAMENTS8 # 4HETIPOFTHEMICROPYLARCELLPROCESSABUTTINGTHEOOLEMMAOFANOOCYTEINLATEVITELLOGENESIS"UNDLESOFMICROTUBULESAND TONOlLAMENTS WITHTHEIRASSOCIATEDMITOCHONDRIA BECOMESPIRALLYTWISTEDASTHEPROCESSELONGATES !BBREVIATIONSCH ZONAPELLUCIDA' 'OLGICOMPLEXMT MICROTUBULESN NUCLEUSO OOCYTETF TONOlLAMENTS

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&IGURE 4RANSMISSIONELECTRONMICROGRAPHSOFENDBULBSOFMICROPYLARCELLSFROMTHECHUMSALMON/NCORHYNCHUSKETA DURINGLATEVITELLOGENESIS&ROM+OBAYASHIAND9AMAMOTO ¶REPRODUCEDWITHPERMISSIONOF*OHN7ILEY3ONS )NC ! 4HEBULBOUSENDOFAMICROPYLARCELL0- HASINVAGINATEDTHESURFACEOFTHEOOCYTE/ !DHAERENSJUNCTIONSAREABUNDANT BETWEENTHEMEMBRANESOFTHETWOCELLS6ESICULARBODIESAND NMlLAMENTSAREABUNDANTINTHEBULB4HEREARELARGE ARROWHEADS ANDSMALLARROWS COATEDVESICLESINTHEOOPLASM"ARM " !DHAERENS JUNCTIONS HAVE DEVELOPED BETWEEN THE MEMBRANEOFTHEPROCESSANDTHEOOLEMMA4HEREISASUGGESTIONOF EXOCYTOTIC ACTIVITY ARROWHEADS ON THE MEMBRANE OF THE MICROPYLAR CELL 0- WHERE IT LIES ADJACENT TO THE OOLEMMA "ARM # %LLIPSOIDALVESICLESAREABUNDANTINTHEOOPLASM/ ADJACENTTOTHELOBULATEDENDOFTHEPROCESS0- "ARM

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&IGURE $IAGRAMS SUMMARIZING CHANGES IN THE MORPHOLOGY AND DISTRIBUTION OF THE YOLK NUCLEUS AND THE NUCLEI OF FOLLICULARCELLSINSECTIONEDOOCYTESOFTHEMEDAKA/RYZIASLATIPES&ROM)WAMATSUAND.AKASHIMA REPRODUCEDWITH PERMISSIONFROMTHE:OOLOGICAL3OCIETYOF*APAN !BBREVIATIONS!& ATTACHINGlLAMENTS&# FOLLICULARCELL./. !& NON ATTACHINGlLAMENTS9. YOLKNUCLEUS

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&IGURE 0HOTOMICROGRAPHSOFLIVINGVITELLOGENICOOCYTESOFTHEMEDAKA/RYZIASLATIPESSHOWINGCHORIONIClLAMENTS THElLAMENTSASSUMEEITHERARIGHT ORLEFT HANDEDSPIRALPATTERN!ISANEARLYSTAGEOFVITELLOGENESISANDTHElLAMENTSDEMON STRATETHERIGHT HANDEDPATTERN"REPRESENTSALATERSTAGEANDITSlLAMENTSSPIRALINALEFT HANDEDDIRECTION,ONG ATTACHINGlLA MENTSWINDONTHEVEGETALHEMISPHERETHESHORTERNON ATTACHINGlLAMENTSADORNTHECHORIONOVERTHEREMAINDEROFTHEOOCYTE 4HEPROXIMALPARTOFTHEATTACHINGlLAMENTSBENDSINTHEDIRECTIONOFTHEANIMALPOLE%ARLYPREVITELLOGENICOOCYTES ABOUT MINDIAMETERARROW ARESHOWNIN"4HESEDISPLAYPRIMORDIALlLAMENTS8&ROM)WAMATSU REPRODUCED WITHPERMISSIONFROMTHE:OOLOGICAL3OCIETYOF*APAN !BBREVIATIONS!0 ANIMALPOLE60 VEGETALPOLE

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&IGURE 4RANSMISSION ELECTRON MICROGRAPHS OF SECTIONS OF PREVITELLOGENIC OOCYTES OF THE MEDAKA /RYZIAS LATIPES SHOWING NON ATTACHING lLAMENTS AMONG THE FOLLICULAR CELLS ' &ROM )WAMATSU REPRODUCED WITH PERMISSION FROM THE:OOLOGICAL3OCIETYOF*APAN ! .ON ATTACHINGlLAMENTS BETWEENFOLLICULARCELLSDURINGLATEPREVITELLOGENESIS4HEFOLLICULAREPITHELIUM' LIESBETWEEN ITSBASEMENTMEMBRANE" ANDTHEZONAPELLUCIDA% !THECALCELL4 OVERLIESTHEBASEMENTMEMBRANE8 " ! NON ATTACHING lLAMENT AT THE CENTRE ORIGINATES FROM THE ZONA PELLUCIDA WHICH CONSISTS OF AN OUTER LAYER % AND ANINNERLAYER, 8 4HEINSETSHOWSTHEOUTERLAYEROFTHEZONAPELLUCIDACOMPOSEDOFELECTRON DENSEAMORPHOUSANDTUBULARSTRUCTURES8

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&IGURE (YPOTHETICAL DIAGRAM TO ILLUSTRATE THE ROTATION OF AN OOCYTE AROUND AN AXIS IN THE FOLLICLE OF THE MEDAKA /RYZIASLATIPES&ROM)WAMATSU REPRODUCEDWITHPERMISSIONFROM"LACKWELL0UBLISHING 4HEOOCYTE WITHITSFOLLICULAR LAYER', ROTATESWITHINTHEBASEMENTMEMBRANE"- ANDTHETHECALLAYER4, PRIORTOTHEDIFFERENTIATIONOFTHEMICRO PYLARCELL-# ATTHEANIMALPOLE!0 THEANTIPODEOFTHEVEGETALPOLE60 ATTHECENTREOFTHEVEGETALPOLEAREA60! 4HE DIRECTION OF ROTATION ARROWS AROUND THE OOCYTE AXIS IS OPPOSITE TO THE DIRECTION OF BENDING OF THE ATTACHING !& AND NON ATTACHING .!& lLAMENTS ON THE CHORION #( !N OOCYTE COULD ROTATE IN EITHER DIRECTION WITHIN THE FOLLICLE /% OVARIANEPITHELIUM

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&IGURE -ICROGRAPHSILLUSTRATINGTHEMICROPYLARAPPARATUSOFTHEHAGlSH%PTATRETUSSTOUTI&ROM+OCHETAL REPRODUCEDWITHPERMISSIONFROM%LSEVIER3CIENCE ! 3CANNINGELECTRONMICROGRAPHOFTHESURFACEOFTHEMICROPYLARBASEWITHPOSSIBLEENTRANCETOTHEMICROPYLARCANALARROW 8 " 0HOTOMICROGRAPHOFASECTIONOFANOOCYTESHOWINGEARLYDEVELOPMENTOFTHEMICROPYLARCANALMCA INTHEZONAPELLUCIDA CH WITHANCHORlLAMENTSNOTYETEVIDENT!REGIONOFTHECANALARROWHEAD HASPENETRATEDINTOTHEOOPLASMO NEAR THEGERMINALVESICLEGV 8"ARM !BBREVIATIONSBL BASALLAMINAFE FOLLICULAREPITHELIUMMO MESOVARIUM # 0HOTOMICROGRAPHOFASECTIONTHROUGHTHEMICROPYLARCANALMCA OPENINGFROMTHEMICROPYLARCUPMCU INTHECHORION CH OFANOVULATEDEGG8"ARM )NSETHIGHERMAGNIlCATIONOFTHEHONEYCOMBBASEOFTHEMICROPYLARCUPADJACENTTOTHECANAL8"ARM

#(!04%2

&IGURE 4HE MICROPYLAR APPARATUS OF AN OOCYTE OF THE HAGlSH -YXINE GLUTINOSA IMMEDIATELY BEFORE SPAWNING &ROM,YNGNES REPRODUCEDWITHPERMISSIONFROM3PRINGER 6ERLAG ! 0HOTOMICROGRAPHOFASECTIONTHROUGHTHEMICROPYLARCANAL4HETHICKFOLLICULAREPITHELIUMF CONSISTSOFCOLUMNARCELLS ANDISSEPARATEDFROMTHECONNECTIVETISSUEB OFTHETHECABYTHEFOLLICULARBASEMENTMEMBRANEP 4HEZONAPELLUCIDAS ISPERFORATEDBYTHEMICROPYLARCANALM &OLLICULARCELLSALONGTHEAXISOFTHEMICROPYLARCANALASSUMEASPINDLEFORMA TIONAX THATCONTINUESASACORDOFCELLSTHROUGHTHEMICROPYLARCANALTOFORMACYLINDRICALEXTENSIONC THATINVAGINATES THEGERMINALDISCOFTHEOOCYTE4HEYOLKYCYTOPLASMOFTHEOOCYTED ISSHOWNATTHEBOTTOM3OMEOFTHEFOLLICULARCELLS FORMINGTHEMICROPYLARCANALAPPEARTOHAVEHOLLOWEDOUTASPACEZ ALONGSIDE8 " 3KETCHOFTHEMICROPYLARAPPARATUSBASEDON&IG!4HEREISAHYALINESTREAKR INTHEGERMINALDISCK ATTHEBASEOF THEMICROPYLARCANAL8 # !SKETCHOFTHEMICROPYLARAPPARATUSATAHIGHERMAGNIlCATION!NOUTGROWTHU OFFOLLICULARCELLSF FORMSACYLINDEROF CELLSC THATINVAGINATESTHEGERMINALDISCD 8

#(!04%2

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MICROVILLIEITHERINVADETHELUMINAOFTHEPORECANALS OR ARE SANDWICHED BETWEEN THE CHORION AND THE OO LEMMA "ENEATHTHEOOLEMMAISTHE #/24)#!, ,!9%2 /& // 0,!3- +OBAYASHI A (ART AND #OLLINS )TISTHICKESTATTHEANIMALPOLEANDGRADUALLYBECOMES THINNER TOWARD THE ANTIPODE 4HE ELECTRON DENSE 0% 2)0(%2!, 2%')/. OF CORTICAL OOPLASM LACKS MOST OF THEORGANELLESFOUNDINTHERESTOFTHECORTEXALTHOUGH PROlLES OF ENDOPLASMIC RETICULUM AND AN OCCASIONAL COATED VESICLE MAY BE DETECTED4HE OOPLASM IS LESS COMPACTINTHE )..%2 2%')/.WHICHCONTAINSTHEMOST CONSPICUOUS ORGANELLES OF THE CORTEX THE SPHERICAL MEMBRANE BOUND #/24)#!, !,6%/,) &IGURES ! TO# /THERORGANELLESOFTHEINNERREGIONAREMITO CHONDRIA CIRCULAR AND TUBULAR PROlLES OF AGRANULAR ENDOPLASMICRETICULUM ANNULATELAMELLAE LYSOSOMES AND 'OLGI COMPLEXES &IGURE " !N ELABORATE ANASTOMOSINGNETWORKOFSMOOTHCISTERNAETHROUGHOUT THECORTICALCYTOPLASMCONSTITUTESTHE #/24)#!, %.$/ 0,!3-)#2%4)#5,5-&IGURE! )TCONSISTSOFISOLATED CIRCULARVESICLESANDTUBULARPROlLESANDFORMSCLOSE ASSOCIATIONSWITHBOTHTHECORTICALALVEOLARMEMBRANES ANDOOLEMMA&IGURES"TO$ %XCEPTBELOWTHEMICROPYLE THEMEMBRANE BOUND CORTICAL ALVEOLI ARE ARRANGED WITHIN THE CORTICAL OO PLASM ALWAYSSEPARATEDFROMTHEOOLEMMABYCYTO PLASM&IGURE 4HEYAREVARIABLEINSIZE ATTAINING DIAMETERSOFTOMINCHUMSALMON/NCORHYN CHUSKETA+OBAYASHI A TOMINMEDAKA /RYZIASLATIPES'ILKEYETAL ANDUPTOM IN&UNDULUSHETEROCLITUS3ELMAN 7ALLACE AND"ARR !N APPARENT FUSION DURING lXATION HAS ARTI FACTUALLY PRODUCED VESICLES GREATER THAN M IN SECTIONSOF&UNDULUSEGGS )NTHESETHREESPECIESTHE CORTICAL ALVEOLI FORM A SINGLE LAYER WITHIN THE CORTI CALOOPLASMBUT INTHEROSEBITTERLING2HODEUSOCEL LATUS THEYOCCURINSEVERALLAYERS/HTAETAL )N THE ZEBRA DANIO "RACHYDANIO RERIO A SINGLE LAYER SURROUNDINGTHESPERMENTRYSITECONTRASTSWITHMULTI

)NTRODUCTION

7ITHINSECONDSOFFERTILIZATIONINTELEOSTSTHEREISAN EXPLOSIVEBREAKDOWNOFTHECORTICALVESICLESOVERTHE ENTIRESURFACEOFTHEEGG 4HECHORIONISLIFTEDAWAY FROMTHEOOLEMMAANDTHE 0%2)6)4%,,).% 30!#%ISCRE ATED!LTHOUGH THIS hCORTICAL REACTIONv IS INDUCED BY THE PENETRATION OF THE OOLEMMA BY A SPERMATOZOON SOME FRESHWATER EGGS MAY BE ACTIVATED hPARTHENO GENETICALLYvBYTHEIRPASSAGEFROMTHEISOTONICBODY mUIDS INTO FRESH WATER DURING SPAWNING (ART 9U AND 'REENHUT (ART AND9U +OBAYASHI A /HTA ET AL (ART AND #OLLINS !CTIVATION OF UNFERTILIZED MARINE EGGS OF THE LONG ROUGH DAB (IPPOGLOSSOIDES PLATESSOIDES LIMANDOI DESCANBEINDUCEDBYTRANSFERRINGTHEMTOSEAWATER ,NNINGAND$AVENPORT

/OLEMMAANDTHE#ORTICAL/OPLASM

"EFOREFERTILIZATION THESURFACEOFANEGGFROMWHICH THECHORIONHASBEENREMOVEDISCOBBLEDWITHHEMI SPHERICAL BULGES REVEALING THE LOCATION OF CORTICAL ALVEOLI BELOW &IGURE "RUMMETT AND $UMONT +OBAYASHI A/HTAETAL (ARTAND #OLLINS 4HEOOLEMMAISDECORATEDBYNUMER OUSMICROVILLIANDMICROPLICAEWHICHARESPARSEROVER THE ELEVATIONS THAN IN THE REGIONS BETWEEN )N SEC TIONS THE MICROPLICAE APPEAR AS ELECTRON DENSE lN GER SHAPEDPROJECTIONS&IGURE" 4HEAPPOSITION OF THE CORTICAL VESICLES TO THE INSIDE OF THE OOLEMMA ISACCOMPANIEDBYANAPPARENTCLEARINGOFMEMBRANE PARTICLESFROMTHESITEOFCONTACTBETWEENTHEAPPOSED MEMBRANESADIMPLEINTHEPARTICLE FREEZONEAPPEARS TO MARK THE SITE OF CONTACT (ART AND #OLLINS &IGURES $ % 4HE OOLEMMA IS CLOSELY ASSOCI ATEDWITHTHECHORIONININTACTEGGSANDTHEFOLDSAND

(ART HASPRESENTEDANEXHAUSIVEREVIEWOFTHISLITERATURE ,ITTLEINFORMATIONISAVAILABLEONEGGSOFOTHERlSHES

#(!04%2

LAYEREDROWSTHROUGHOUTTHEREMAINDEROFTHEOOPLASM (ARTAND$ONOVAN .EARTHESPERMENTRYSITE OF"RACHYDANIO THEALVEOLIARETOMINDIAM ETER AND ARE DENSELY PACKED FROM THIS REGION TO THE VEGETAL POLE THEY PROGRESSIVELY INCREASE IN SIZE AND BECOMESPARSERSOTHATAGRADIENTISESTABLISHEDINTHE STRUCTURALORGANIZATIONOFTHEEGGCORTEXFROMTHESITE OFSPERMENTRYTOTHEVEGETALPOLE 4HEREISINDIRECTEVIDENCEFORTHEPRESENCEOFACTIN ANDACTIN CONTAININGlLAMENTSWITHINTHECORTICALOO PLASM(ARTAND7OLENSKI 7OLENSKIAND(ART B A -ICROlLAMENTSTONMINDIAMETER HAVEBEENDESCRIBEDINTHECORESOFMICROPLICAEANDIN THECORTICALLAYERNEARTHESPERMENTRYSITEOF"RACHY DANIO 7OLENSKI AND (ART A 4HE PRESENCE OF ACTIN WAS DEMONSTRATED JUST BENEATH THE OOLEMMA OF UNACTIVATED EGGS USING RHODAMINE PHALLOIDIN AND mUORESCENCEMICROSCOPY7OLENSKIAND(ART B )TISSUGGESTEDTHATBUNDLESOFACTINlLAMENTSDISPLACE MEMBRANOUS ORGANELLES FROM THE CORTEX AND MAY BE IMPORTANTINMAINTAININGTHEOVERALLSHAPEOFTHEEGG AND PLICAE )N EGGS OF THE CHUM SALMON THEY MAY ASSIST IN EXPULSION OF THE CORTICAL ALVEOLI DURING THE CORTICALREACTION+OBAYASHI A

#ORTICAL!LVEOLI

!N ELECTRON DENSE CORE SURROUNDED BY AN ELECTRON LUCENT HALO HAS BEEN DESCRIBED IN CORTICAL ALVEOLI OF SEVERAL SPECIES &IGURE " )WAMATSU AND /HTA +UDO (ART AND 9U (ART AND $ONOVAN +OBAYASHI A )N EGGS OF "RACHYDANIO THECORECONSISTSOFTIGHTLY PACKEDPAR TICLESTONMINDIAMETERTHESEARESURROUNDEDBY LESSCOMPACT CIRCULARlBRILLO GRANULARAGGREGATES TO NM IN DIAMETER &IGURES ! TO # (ART AND #OLLINS 3OMETIMES CORTICAL ALVEOLI ARE OB SERVEDLACKINGTHEHALOINTHEZEBRAlSHTHEPERIGRANU LARMEMBRANEENCLOSESAMASSOFSMALLPARTICLESOFA SIMILARSIZETOTHOSEOFTHECENTRALMASSOFTHECORED PARTICLES &IGURE $ #ORTICAL GRANULES OF 3ALMO GAIRDNERI SHOW AN ELECTRON LUCENT CORE SURROUNDED BYELECTRON DENSEMATERIAL&IGURE )NOUEETAL 4HEREARETWOTYPESOFCORTICALALVEOLIINEGGS OF THE ROSE BITTERLING /HTA ET AL ALVEOLI OF THEANIMALPOLECONTAINELECTRON LUCENTDROPLETSSUS PENDEDWITHINANELECTRON DENSEMATRIX&IGURE! WHEREAS AT THE VEGETAL POLE THE CONTENTS ARE HOMO GENEOUSANDELECTRONDENSE&IGURE" )NADDITION TOCORTICALALVEOLI MEMBRANE BOUNDGRANULES PACKED

WITH lNELY GRANULAR OR HOMOGENEOUS MATERIAL HAVE BEENDESCRIBEDINTHECORTICALOOPLASMOFUNFERTILIZED EGGSOFCARP#YPRINUSCARPIOANDGOLDlSH#ARASSIUS AURATUS&IGURE +UDO $ESIGNATEDAS#! '2!.5,%3 THEYAREMUCHSMALLERTHANCORTICALALVEOLI ANDSCATTEREDAROUNDTHEM4HEYAREMOREPLENTIFULIN THEANIMALTHANTHEVEGETALHEMISPHERE #ORTICAL ALVEOLI CONTAIN GLYCOPROTEINS 4HEY STAIN WITH PERIODIC ACID 3CHIFF REAGENT ALCIAN BLUE AT LOW P( COLLOIDALIRON ANDBROMPHENOLBLUE ANDAREOF TEN METACHROMATIC WITH TOLUIDINE BLUE SUGGESTING THATTHEYCONTAINANACIDICGLYCOCONJUGATECONSISTING OF A POLYSACCHARIDE AND PROTEIN THAT IS ACID MUCO POLYSACCHARIDE ANDOR MUCOPROTEIN REVIEWED BY (ART !UNIQUECLASSOFGLYCOPROTEINSSHARING CHARACTERISTICBIOCHEMICALANDBIOLOGICALFEATURESHAS BEEN DESIGNATED (9/3/0(/2). AND IS ASSOCIATED WITH CORTICAL ALVEOLI OF SEVERAL SPECIES +ITAJIMA )NOUE AND )NOUE )N FACT IT HAS BEEN SUGGESTED THAT THESE GLYCOPROTEINS NOT SULPHATED MUCOPOLYSACCHA RIDES ARETHEMAJORWATER SOLUBLECOMPONENTSOFCOR TICAL ALVEOLI )NOUE ET AL ( (9/3/0(/2). HAS BEENDElNEDASTHEMAJORGLYCOPROTEINOFTHECORTICAL ALVEOLI AND THEREFORE DERIVED FROM THE 'OLGI COM PLEX WITH A HIGH CARBOHYDRATE CONTENT TO WW WHOSE PROTEIN CORE COMPRISES TANDEM REPETI TIONS OF IDENTICAL PROTEIN SEQUENCES IT IS COMPLETELY CLEAVED INTO REPEATING UNITS , (9/3/0(/2). FOLLOW INGTHECORTICALREACTION+ITAJIMA )NOUE AND)NOUE !LTHOUGHTHElRSTHYOSOPHORINSDESCRIBEDWERE POLYSIALOGLYCOPROTEINS NOTALLBELONGTOTHISCATEGORY 4AGUCHIETAL $ESPITEDIFFERENCESINSEQUENCE HOWEVER HYOSOPHORINSFROMDIFFERENTSPECIESOFlSH ARECHARACTERIZEDBYTHEPRESENCEOFEITHERPOLYANIONIC ANDOR BULKY MULTIANTENNARY STRUCTURES &IGURE !POLYSIALOGLYCOPROTEINOFK$AWASISOLATEDFROM UNFERTILIZEDEGGSOFTHERAINBOWTROUT3ALMOGAIRDNERI )NOUEAND)NOUE +ITAJIMA )NOUE AND)NOUE )NOUE ET AL )T IS COMPOSED OF A SMALL PROTEINCOREOFK$ATOWHICHARECOVALENTLYBOUND MULTIPLY BRANCHED VARIABLY ELONGATED OLIGO AND POLYSIALYLGLYCANCHAINS4HECORECONSISTSOFACOM PLETETANDEMREPEATOFABOUTTRIDECAPEPTIDEUNITS 3IMILARPOLYSIALOGLYCOPROTEINSHAVEBEENREPORTEDIN EGGS OF OTHER SALMONIDS AND SHOW A HIGH DEGREE OF HOMOLOGY +ITAJIMA ET AL )N THE KOKANEE SALMON/NCORHYNCHUSNERKA HOWEVER THEHYOSOPHO RINOFTHEUNFERTILIZEDEGGISUNIQUEINTHATTWOPOLYSI ALYLGLYCAN CHAINS ARE CHARACTERIZED ONE CONTAINS AMINO ACIDS THE OTHER AND IN THE OPINION OF

%6%.43!33/#)!4%$7)4(&%24),):!4)/.

3ONG +ITAJIMA AND )NOUE THESE DIFFERENCES ARESUFlCIENTTOCASTDOUBTONTHEPLACEMENTOFTHEKO KANEEINTHE'ENUS/NCORHYNCHUS4HEHYOSOPHORIN OF THE mOUNDER 0ARALICHTHYS OLIVACEUS DIFFERS FROM THATOFOTHERlSHINPOSSESSINGANOVELPENTAANTENNARY CARBOHYDRATESTRUCTUREWITHAlVE TINEDCARBOHYDRATE FORKATTACHEDTOTHEREPEATINGDECAPEPTIDEOFTHEPRO TEINCORE&IGURE 3EKOETAL !TTEMPTS TO LOCATE HYOSOPHORIN WITHIN CORTICAL ALVEOLI BY MORPHOLOGICAL METHODS HAVE BEEN DISAP POINTING )NOUE ET AL )T IS DIFlCULT TO RAISE ANTIBODIES TO HYOSOPHORIN PERHAPS BECAUSE OF THE UNUSUAL CHEMICAL STRUCTURE OF BOTH THE CARBOHYDRATE PROSTHETIC GROUPS AND THE APOPROTEIN SO THAT IMMU NOCYTOCHEMICAL METHODS HAVE BEEN OF LITTLE HELP )NADDITION THELARGEAMOUNTSOFYOLKWITHINTHEMA TURE EGG HAVE HINDERED STUDIES OF THE CORTEX (YO SOPHORIN HAS BEEN IDENTIlED HOWEVER IN A FRACTION RICH IN CORTICAL ALVEOLI OBTAINED FROM HOMOGENIZED SALMONEGGSBYLOW SPEEDCENTRIFUGATION ,%#4).3 SPECIFIC CARBOHYDRATE BINDING PROTEINS COMMONLYFOUNDINPLANTS HAVEBEENDESCRIBEDINTHE EGGSOFVARIOUSlSH+RAJHANZL (OREJSI AND+OKOU REK A B !LLKNOWNLECTINSCONTAINTWOORMORE BINDING SITES FOR CARBOHYDRATE UNITS AND CAN AGGLU TINATE OR CROSS LINK CELLS ,ECTINS HAVE BEEN LOCAL IZED BY IMMUNOLOGICAL METHODS WITHIN THE CORTICAL ALVEOLI OF PREVITELLOGENIC OOCYTES +RAJHANZL ET AL A B .OSEK AND IN THE THIN LAYER OF COR TICAL ALVEOLI OF MATURE EGGS THAT HAVE NOT UNDERGONE ACTIVATION .OSEK +RAJHANZL AND +OCOUREK ,ECTINS ARE SYNTHESIZED DURING PREVITELLOGEN ESISINTHE'OLGICOMPLEX.OSEK ANDINCREASE INAMOUNTDURINGLATERSTAGESWHENCORTICALALVEOLIlLL THEENTIREOOPLASMBEFOREMOVINGTOTHEPERIPHERYAS THE OOCYTE ACCUMULATES YOLK .OSEK +RAJHANZL AND +OCOUREK 4HELECTINSAREDISCHARGEDINTOTHE PERIVITELLINESPACEFOLLOWINGTHECORTICALREACTIONAND ITISSUGGESTEDTHATTHEYCONTRIBUTETOTHEPHYSIOLOGICAL MECHANISMSPREVENTINGPOLYSPERMYBYAGGLUTINATING SUPERNUMERARY SPERMATOZOA .OSEK +RAJHANZL AND +OCOUREK +UDO AND )NOUE 4HEY MAY ALSOAGGLUTINATEPATHOGENICBACTERIATHATPENETRATETHE OUTER ENVELOPES OF THE EGG THEREBY PREVENTING THEM FROMATTACKINGTHEEGG

&ERTILIZATION

3PERMATOZOAOFMOSTTELEOSTEANlSHESHAVENOACRO SOMALAPPARATUSANDGAINACCESSTOTHESURFACEOFTHE EGGTHROUGHTHEMICROPYLETHATPERFORATESTHECHORION )WAMATSUAND/HTA B+UDO B "RUMMETTAND$UMONT 'ILKEY +OBAYAS HI AND9AMAMOTO /HTA AND )WAMATSU /HTA 7OLENSKI AND (ART A "ERN AND !VTALION /HTA /HTA AND .ASHIRO ZAWA 4HE lRST SPERMATOZOON ARRIVING AT THE MICROPYLENAVIGATESTHECANALTOREACHTHEOOLEMMAL MICROVILLI AT THE 30%2- %.429 3)4% &IGURES ! " ! " AND )TATTACHESTOTHESEMICRO VILLIAND INSOMESPECIES ISRAPIDLYENGULFEDBEFORE THE OOLEMMA ELEVATES TO FORM THE &%24),):!4)/. #/.% &IGURES TO )WAMATSU AND /HTA B /HTAAND)WAMATSU )WAMATSU )NOTHER SPECIES HOWEVER THE FERTILIZATION CONE MAY DEVELOP EITHERBEFOREORATTHESAMETIMEASTHESPERMATOZOON ISINCORPORATED+UDO B+UDOAND3ATO +OBAYASHIAND9AMAMOTO 7OLENSKIAND (ART A &OLLOWING PENETRATION OF THE SPERM IN THE ROSE BITTERLING 2HODEUS OCELLATUS OCELLATUS THE SPERMENTRYSITETRANSFORMSINTOA 37/,,%. -!33THAT PLUGSTHEMICROPYLEANDPREVENTSPENETRATIONOFEXCESS SPERMATOZOA &IGURE /HTA AND .ASHIROZAWA 4HESWOLLENMASSMAYBEATYPEOFFERTILIZATION CONEITAPPEARSIDENTICALINFORMANDFUNCTIONEXCEPT THATFERTILIZATIONCONESRECEDEQUICKLYAFTERFUSIONOF THEMEMBRANESOFTHEGAMETESBUTTHESWOLLENMASS PERSISTSANDAPPEARSTOFUNCTIONASAMICROPYLARPLUG 4HEEXPANDEDSURFACEAREAAFFORDEDBYTHECLUSTER OFMICROVILLIATTHESPERMENTRYSITEMAYEXPEDITETHE BINDING FUSION PROCESS 7OLENSKI AND (ART A 4HERE HAVE BEEN SUGGESTIONS THAT THE INTERACTION BE TWEEN THE SPERMATOZOON AND THE SPERM BINDING SITE RESULTS FROM SPECIlC RECEPTORS IN THE MEMBRANE OF THE MICROVILLI THAT RECOGNIZE ANDOR BIND WITH THE PLASMA MEMBRANE OF THE SPERMATOZOON /HTA AND )WAMATSU 7OLENSKI AND (ART A /HTA (OWEVER SINCE SPERMATOZOA CAN FERTILIZE A DECHORIONATEDEGGATANYPOINTONITSSURFACE3AKAI )WAMATSUAND/HTA RECEPTORSFORSPER MATOZOA IFTHEYEXIST MUSTBEPRESENTOVERTHEENTIRE OOLEMMA'ILKEY

!N EXHAUSTIVE REVIEW OF THE RECENT LITERATURE ON FERTILIZATION IN TELEOSTSHASBEENPRESENTEDBY)WAMATSU

#(!04%2

3PERMATOZOA OF TILAPIA /REOCHROMIS NILOTICUS REACH THE MICROPYLE IN LESS THAN SECOND AND ATTAIN THESPERMBINDINGSITEONTHEOOLEMMAWITHINTO SECONDSAFTERINSEMINATION"ERNAND!VTALION %NGULFMENTOFTHEHEADINTHISSPECIESISALWAYSFOL LOWEDBYANINDENTATIONOFTHEOOLEMMATHE#,%&4/& 0%.%42!4)/.&IGURE 4HESPERMTAILISSTILLVIS IBLEPROTRUDINGFROMTHEOOLEMMATOMINUTESAF TERINSEMINATION4HEMICROVILLIOFTHESPERMBINDING SITE GRADUALLY DISAPPEAR FOLLOWING PENETRATION OF THE SPERMATOZOON PERHAPS DEPRIVING OTHER SPERMATOZOA OFRECEPTORS THEREBYPLAYINGAROLEINTHEPREVENTION OFPOLYSPERMY &ORMATION OF A TWO TIERED FERTILIZATION CONE HAS BEENDESCRIBEDINSOMESPECIES)NFERTILIZEDEGGSOF THEAYUlSH0LECOGLOSSUSALTIVELIS THElRSTFERTILIZATION CONEISACYLINDRICALSTRUCTURE ABOUTMLONGAND TOMINDIAMETER THATRISESFROMTHESPERMENTRY SITEWITHINTOSECONDSOFIMMERSIONINFRESHWA TER&IGURE +UDOB !TABOUTSECONDS A SECONDTIERFORMSAPEDESTALABOUTMHIGHELEVAT INGTHElRSTCONEFROMITSAPEX!FTERABOUTSECONDS THISSTRUCTURERECEDESTOFORMAMOUNDONTHESURFACE OFTHEEGGWITHTHESPERMTAILEXTENDINGFROMIT!LESS ELABORATE TWO TIERED FERTILIZATION CONE APPEARS IN THE CARP#YPRINUSCARPIO)TREACHESAHEIGHTOFMORETHAN MANDABREADTHOFTOMWITHINSECONDSOF IMMERSIONOFFERTILIZEDEGGSINFRESHWATER RESULTING INATRANSIENTPLUGGINGOFTHEMICROPYLE&IGURE +UDO AND 3ATO 7ITHIN TO MINUTES THE SECONDTIERAPPEARSATITSBASE4HEEARLIERCONESHORT ENS A VOLCANO LIKE STRUCTURE RISES IN THE MICROPYLAR REGIONAND EXTENDINGFROMTHECENTREOFITSCRATER IS THETWO TIEREDFERTILIZATIONCONEBRANDISHINGTHESPERM TAILFROMITSAPEX&IGURE 4HEELKHORNSCULPIN!LCICHTHYSALCICORNISPROVIDES A CONVENIENT MODEL FOR STUDYING THE EARLY STAGES OF FERTILIZATION -UNEHARA 4AKANO AND +OYA +OYA 4AKANO AND4AKAHASHI 4HISCOTTIDDEM ONSTRATEShINTERNALGAMETICASSOCIATIONvWHERESPERM INTRODUCEDINTOTHEOVARIANCAVITYBYCOPULATION ENTER THEMICROPYLARCANALSOFOVULATEDEGGSBUTTHEREISNO SPERMEGGFUSIONUNTILTHEEGGSARERELEASEDINTOSEA WATER &IGURE $URING EXPERIMENTAL MANIPULA TIONS SPERMREMAINATTACHEDTOTHEOOPLASMICSURFACES OF EGGS FRESHLY STRIPPED FROM COPULATED FEMALES AND FERTILIZATIONISINITIATEDWHENTHEEGGSAREIMMERSEDIN SEAWATER"YSECONDSAFTERIMMERSION AFERTILIZING SPERMATOZOONPENETRATESTHEOOPLASMFORABOUTHALFITS HEADLENGTHANDSEVERALVESICLESAPPEARINTHEAREAOF

PENETRATION&IGURE! !SVESICULATIONADVANCES THEPLASMAMEMBRANEOFTHESPERMDISAPPEARS THERE BYEXPOSINGTHENUCLEARMEMBRANEOFTHESPERMTOTHE OOPLASM ! FERTILIZATION CONE FORMS AROUND THE UN PENETRATEDPORTIONOFTHESPERMHEADANDANELECTRON DENSETRIANGULARREGION CONTAININGNOORGANELLESOTHER THAN RIBOSOMES APPEARS IN THE OOPLASM SURROUNDING THE PENETRATING SPERM HEAD &IGURES " # 4HEMICROTUBULESOFTHESPERMTAILDEGENERATEBY SECONDSANDTHEREISALOSSOFMOTILITY&IGURE$ 4HEMITOCHONDRIAOFTHESPERMREMAINOUTSIDETHEOO LEMMA "Y TO MINUTES THE SPERM HAS PENETRATED UP TO ITS MIDPIECE "Y MINUTES AFTER IMMERSION THE NUCLEAR MEMBRANE OF THE SPERM SEPARATES FROM THECHROMATIN BEGINNINGATTHEANTERIORREGIONOFTHE SPERMHEAD&IGURES% & "YMINUTES NOTRACE OF THE SPERM CAN BE DETECTED AND A SEPARATING POLAR BODYISNOTICABLEULTRASTRUCTURALLY&IGURE' !LTHOUGHINSEMINATIONTAKESPLACEINTWOSPECIESOF 3OUTH!MERICANCATlSHESOFTHEFAMILY!UCHENIPTERI DAE ITISNOTCLEARTHATFERTILIZATIONISINTERNAL-EISNER ETAL 4HEMALEHASA '/./0/$)5-ORINTROMIT TENT ORGAN FORMED FROM AN ELONGATED GENITAL PAPILLA ANDMODIlEDANALlN&IGURES! " 4HEPRESENCE OFSPERMWITHINTHETORTUOUSFOLDSANDNARROWDEPRES SIONS OF THE OVARIAN CAVITY SHOWS THAT INSEMINATION HASOCCURRED&IGURES# $ BUTNOFERTILIZEDEGGS OR EARLY EMBRYOS HAVE BEEN DEMONSTRATED IN EITHER SPECIES4HEREAPPEARTOBENODISTINCTSTORAGESTRUC TURESAND INMANYCASES THESPERMSEEMTOBEEMBED DEDWITHINTHEEPITHELIUMLININGTHECAVITY3INCETHE TIMEANDPLACEOFFERTILIZATIONARENOTKNOWN ITMAY BETHAT ASINTHECASEOFTHESCULPIN FERTILIZATIONDOES NOTOCCURUNTILTHEEGGSREACHSEAWATER 5NLIKETHESITUATIONINMOSTlSH SPERMATOZOAOFTHE WHITE STURGEON !CIPENSER TRANSMONTANUS POSSESS AN !#2/3/-%ATTHEANTERIOREND#HERRAND#LARK 4HIS CAPLIKE MEMBRANE BOUND SAC CONTAINS ENZYMESTHATARERELEASEDDURINGTHE!#2/3/-!,2%!# 4)/.ANDAREBELIEVEDTOFACILITATEENTRYOFTHESPERM INTOTHEOVUM&IGURE )TISAMYSTERYWHYAN ACROSOME IS NEEDED IN THE STURGEON WHEN THE SPERM ISABLETOGAINACCESSTOTHEOVUMBYWAYOFMULTIPLE MICROPYLES !NINSOLUBLEK$AGLYCOPROTEINFROM LAYER , LOCATED IMMEDIATELY INSIDE THE INSOLUBLE JELLYCOAT, OFTHEEGGENVELOPE UNDERGOESPROTE OLYSISTOPRODUCEASOLUBLEK$AGLYCOPROTEINWHICH INDUCESTHEACROSOMALREACTIONINHOMOLOGOUSSPERM BUTFAILSTODOSOINSPERMOFTHE'REAT,AKESSTURGEON !FULVESCENS

%6%.43!33/#)!4%$7)4(&%24),):!4)/.

4HERE IS NO MICROPYLE IN THE LAMPREYS ,AMPETRA mUVIATILISAND,PLANERIANDITISUNCLEARHOWFERTIL IZATIONISACCOMPLISHED+ILLE !FZELIUS .ICA NDER AND3JÚDÏN .ICANDER AND3JÚDÏN 4HESPERMATOZOONHASANACROSOMEANDISORIENTEDAT RIGHTANGLESTOTHEANIMALPOLEOFTHEEGGBYTHEAPICAL &)"2/5345&4&IGURE WHOSEFIBRILSAPPEARCONTIN UOUSWITHTHOSEINTHEPORECANALSOFTHEOUTERCHORION &IGURE )TISSUGGESTEDTHATPROTEOLYTICENZYMES FROM THE SPERMATOZOON DISSOLVE A PASSAGE THROUGH THECHORIONBYWAYOFTHEPORECANALS7ITHINMIN UTESOFSTRIKINGTHECHORION TAILMOVEMENTSCEASEAND THE SPERMATOZOON SLIPS PASSIVELY THROUGH THE INNER LAYEROFTHECHORIONANDCROSSESTHEPERIVITELLINESPACE 7HENTHESPERMATOZOONEMBEDSITSELFINTHECHORION A (%!$ &),!-%.4 IS THRUST FORWARD FROM ITS HEAD AND BECOMES ATTACHED TO THE EGG CORTEX &IGURE ACTIVATING THE EGG! hTHIN THREADv OF OOPLASM RISES TO MEET IT AND THE SPERMATOZOON PERHAPS DRAWN BY ELASTICITYOFTHECORTICALOOPLASMICSTRAND PENETRATES THE OOLEMMA .O SUPERNUMERARY SPERMATOZOA ARE SEENINTHEPERIVITELLINESPACE

#ORTICAL2EACTION

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4HE AVERAGE RESTING POTENTIAL OF UNFERTILIZED MEDAKA EGGS IN 2INGERS SOLUTION IS n M6 &OLLOWING FERTILIZATIONINDILUTE2INGERSSOLUTION THEMEMBRANE DEPOLARIZESOVERAPERIODOFSECBYAFEWMIL LIVOLTS PRESUMABLYBYTHEINmUXOF#AAND.AIONS ANDEFmUXOF+$EPOLARIZATIONISFOLLOWEDBYALONG HYPERPOLARIZING PHASE WITH AN AVERAGE AMPLITUDE OF M6 )T IS SUGGESTED THAT TWO CHANGES IN THE OOLEMMA BRING ABOUT AN INCREASE IN ITS PERMEABILITY TO+DURINGHYPERPOLARIZATIONAND+mOWSBACKINTO THEOOPLASM&IRST THERISEININTERNALFREE#AMAY CAUSEANOPENINGOF+CHANNELSAND SECONDLY NEW +CHANNELSMAYBEADDEDTOTHESURFACEBYTHEINCOR PORATIONOFNEWMEMBRANEASARESULTOFTHEEXOCYTOSIS OFTHECORTICALVESICLES2ECOVERYFROMHYPERPOLARIZA TIONHASAFASTPHASELASTINGSECFOLLOWEDBY ASLOWERRATEOFCHANGEWHICHREACHESASTEADYPOST FERTILIZATIONRESTINGPOTENTIALOFnM6BY MINAFTERFERTILIZATION $URINGTHECORTICALREACTION THEMEMBRANESOFTHE CORTICALVESICLESFUSEWITHTHEOOLEMMAANDTHEREOC CURSASUDDENMASSIVEEXOCYTOSIS&IGURES * + AND )WAMATSUAND/HTA (ART 9U AND 'REENHUT 3HACKLEY AND +ING )WAMATSUAND+EINO (ARTAND9U "RUM METTAND$UMONT +OBAYASHI A3CHALKOFF AND(ART (ARTAND#OLLINS /NEORMORE OPENINGSAPPEARINTHEOOLEMMAANDTHECONTENTSOF THE ALVEOLI ARE RELEASED INTO THE PERIVITELLINE SPACE &IGURE *USTBEFOREEXPULSION ACOATINGOFCOM PACT OOPLASM ENVELOPS THE CORTICAL ALVEOLI OF SOME SPECIESTHISCOATEVENTUALLYCOALESCESWITHTHEDENSE PERIPHERAL OOPLASM AS EXOCYTOSIS CONTINUES &IGURES AND )WAMATSUAND/HTA +OBAYASHI A !WIDE TRANSIENT #2!4%2OR #2904 LINEDWITH MEMBRANEOFLOWPARTICLEDENSITY REMAINSONTHESUR FACEATTHESITEOFTHEEXPULSION&IGURE! ANDTHE DIFFERENCESINPARTICLEDENSITYAREMAINTAINEDBETWEEN THEDOMAINSOFTHEFORMERCORTICALVESICLEANDTHEOO LEMMA EVENAFTERMOSTEVIDENCEOFEXOCYTOSISHASDIS APPEAREDFROMTHESURFACE SUGGESTINGTHATCONSTITUENTS OFTHETWOMEMBRANEDOMAINSREMAINDISTINCTANDDO NOTREADILYINTERACT&IGURE" (ARTAND#OLLINS ,ARGENUMBERSOFMICROVILLISPROUTWITHINTHE CRATERSOFSOMESPECIES BEGINNINGATTHEOPENINGAND SPREADINGTHROUGHOUTEVENTUALLYTHESEMICROVILLIDIS APPEARASTHECRATERSSHRINK&IGURE )WAMATSU AND /HTA )WAMATSU AND +EINO "RUM METTAND$UMONT +OBAYASHI A

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MAY ALSO CONTRIBUTE TO THE INmUX OF WATER ,NNING AND$AVENPORT 4RANSPARENT 30(%2)#!, "/$)%3 ARE VISIBLE WITHIN THE PERIVITELLINE SPACE SHORTLY AFTER THE CORTICAL REAC TIONBEGINS4HESEAREREMNANTSOFTHEELECTRON DENSE CORESOFTHECORTICALALVEOLITHATSWELLAND INTHELIVING EGG BECOMEMORETRANSPARENTINTHEMEDAKA/RYZIAS LATIPES THEYATTAINDIAMETERSOFTOM7ITHTHE SCANNING ELECTRON MICROSCOPE THEY APPEAR AS DENSE SPHERULESONTHEINSIDEOFTHECHORION&IGURE 3PHERICALBODIESREMAINVISIBLEFORSOMETIMEDURING DEVELOPMENT )T IS SUGGESTED THAT THE OOLEMMA AND CHORIONAREHELDAPART ATLEASTINPART BYTHEPHYSICAL PRESENCEOFTHESEBODIES)WAMATSUAND/HTA 7ITH THE RELEASE OF THE ALVEOLAR CONTENTS INTO THE PERIVITELLINE SPACE A SPECIAL PROTEASE APPEARS THAT CLEAVESTHELARGE( HYOSOPHORINMOLECULESINTOTHEIR LEASTREPEATINGUNITS , HYOSOPHORIN ANDTHESEBECOME A MAJOR CONSITUENT OF THE PERIVITELLINE mUID )NOUE AND)NOUE )NOUEETAL 4HEDEPOLYMER IZATION APPEARS TO BE COMPLETE WITHIN MINUTES OF FERTILIZATION4HEENZYMEISAUNIQUEPROTEINASE (9/ 3/0(/2).!3%+ITAJIMA )NOUE AND)NOUE THAT ISPROBABLYPRESENTINANINACTIVEFORM TOGETHERWITH ( HYOSOPHORIN WITHIN THE CORTICAL ALVEOLI +ITAJIMA AND )NOUE 0RESUMBLY ITS ACTIVITY IS INHIBITED IN THE DORMANT EGG BY THE HIGH IONIC STRENGTH WITH IN THE ALVEOLI AND FOLLOWING EXOCYTOSIS IT BECOMES ACTIVE IN THE LOW IONIC CONCENTRATIONS OF SALT WITHIN THEPERIVITELLINEmUID)THASBEENSUGGESTEDTHATONE OFTHEFUNCTIONSOF, HYOSOPHORINMAYBEASANOSMO REGULATOR IN THE PERIVITELLINE SPACE +ITAJIMA )NOUE AND)NOUE , HYOSOPHORINMOLECULESHAVEBEEN REPORTEDINTHEmUIDSSURROUNDINGSALMONIDEMBRYOS UNTILHATCHING

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&IGURE %LECTRON MICROGRAPHS OF THE UNACTIVATED EGG OF THE ZEBRAlSH "RACHYDANIO RERIO TO ILLUSTRATE THE CORTICAL ENDOPLASMICRETICULUM&ROM(ARTAND#OLLINS REPRODUCEDWITHPERMISSIONFROM3PRINGER 6ERLAG ! &REEZE FRACTUREREPLICASHOWINGTHECORTICALENDOPLASMICRETICULUMARROWHEADS BRANCHINGINTHECORTICALCYTOPLASM 8 !BBREVIATIONS' 'OLGICOMPLEX- MITOCHONDRION " # 2EPLICAS SHOWING THE CLOSE APPOSITION BETWEEN THE CORTICAL ENDOPLASMIC RETICULUM AND THE OOLEMMA 0 IN " AND THEMEMBRANEOFACORTICALGRANULE#'- IN#"8 #8 $ 4RANSMISSION ELECTRON MICROGRAPH TO ILLUSTRATE THE NARROW GAP SEPARATING THE CORTICAL ENDOPLASMIC RETICULUM AND OOLEMMA0 8

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&IGURE $IAGRAM OF AN UNFERTILIZED EGG OF THE MEDAKA /RYZIAS LATIPES MM IN DIAMETER &ROM 'ILKEY REPRODUCEDWITHKINDPERMISSIONFROMTHE3OCIETYFOR)NTEGRATIVEAND#OMPARATIVE"IOLOGY !SPERMWILLCROSSTHECHORION #H VIATHEMICROPYLE- ENTERTHECYTOPLASM#Y ANDINITIATEAWAVEOFCORTICALVESICLESECRETION6ESICLESAREINDICATED BY SMALL CIRCLES -OST OF THE EGG IS OCCUPIED BY THE MEMBRANE BOUND YOLK COMPARTMENT 9 4HE CYTOPLASMIC THICKNESS MM ISEXAGGERATEDANDOILDROPLETSAREOMITTEDFORCLARITY

&IGURE #ORTICAL GRANULES FROM UNACTIVATED EGGS OF THE ZEBRAlSH "RACHYDANIO RERIO &ROM (ART AND #OLLINS REPRODUCEDWITHPERMISSIONFROM3PRINGER 6ERLAG ! %LECTRONMICROGRAPHOFAREPLICAOFAFREEZE FRACTUREDCORTICALGRANULESHOWINGCENTRAL# ANDPERIPHERAL0 CONTENTS WITHINMEMBRANEARROWHEADS 8 " !HIGHERMAGNIlCATIONOFTHEREPLICASHOWINGCONTENTSOFTHECENTRALREGIONONTHELEFT PERIPHERALCONTENTSONTHERIGHT 8 # 4RANSMISSIONELECTRONMICROGRAPHOFASECTIONOFACORTICALGRANULESHOWINGTHElBRILLO GRANULARMESHWORKOFTHEPERIPH ERALCONTENTS8 $ 3OME CORTICAL GRANULES LACK THE PERIPHERAL HALO 4HIS ELECTRON MICROGRAPH OF A REPLICA OF A FREEZE FRACTURED CORTICAL GRANULESHOWSONLYSMALLPARTICLESWITHINTHELIMITINGMEMBRANEARROWHEADS 8

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&IGURE 4RANSMISSIONELECTRONMICROGRAPHOFASECTIONOFCORTICALGRANULESOFRAINBOWTROUT3ALMOGAIRDNERI4HEGRAN ULECONSISTSOFANELECTRON LUCENTSPHERICALCOREANDANELECTRON DENSEPERIPHERALREGION"ARM&ROM)NOUEATAL REPRODUCEDWITHPERMISSIONFROM%LSEVIER3CIENCE

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&IGURE 4HE , HYOSOPHORIN OF THE mOUNDER 0ARALICHTHYS OLIVACEUS DIFFERS FROM THAT OF OTHER lSH IN POSSESSING A PENTAANTENNARY CARBOHYDRATE STRUCTURE &ROM 3EKO ET AL REPRODUCED WITH PERMISSION FROM THE !MERICAN 3OCIETY FOR"IOCHEMISTRYAND-OLECULAR"IOLOGY

&IGURE 4RANSMISSION ELECTRON MICROGRAPH OF A SECTION THROUGH THE MICROPYLAR REGION OF AN UNFERTILIZED EGG OF THE BITTERLING 2HODEUS OCELLATUS &ROM /HTA ¶ REPRODUCED WITH PERMISSION OF *OHN7ILEY 3ONS )NC 4HERE ARE WELL DEVELOPEDMICROVILLIORMICROPLICAE ATTHESPERMENTRYSITE33 ONTHEEGGSURFACEBENEATHTHEMICROPYLE#( CHORION 8

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&IGURE -ICROGRAPHS OF SECTIONS OF EGGS OF THE ZEBRAlSH "RACHYDANIO RERIO IN THE REGION OF THE MICROPYLE TAKEN SECONDSAFTERINSEMINATION&ROM7OLENSKIAND(ART BREPRODUCEDWITHPERMISSIONFROM"LACKWELL0UBLISHING ! 0HOTOMICROGRAPHOFANEGGWHICHHASCOMPLETELYINCORPORATEDTHESPERMHEADARROW 4HEREISNOEVIDENCEOFAFERTILIZA TIONCONE4HECORTICALGRANULESARROWHEADS HAVENOTBROKENDOWNANDTHECHORION# HASNOTRAISEDFROMTHEOOLEMMA 8 " 4RANSMISSIONELECTRONMICROGRAPHOFTHESAMEEGGSHOWINGTHESPERMNUCLEUS3 BENEATHTHEOOLEMMA4HECYTOPLASM ATTHESPERMENTRYSITEISRAISEDSLIGHTLY8

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&IGURE $IAGRAMMATICREPRESENTATIONOFTHEEVENTSASSOCIATEDWITHSPERMPENETRATIONINEGGSOFTHEMEDAKA/RYZIAS LATIPESASSEENWITHTHESCANNINGELECTRONMICROSCOPEFOLLOWINGlXATIONANDREMOVALOFTHECHORION4IMESAFTERINSEMINATION AREINDICATEDINSECONDS2APIDENGULFMENTOFTHESPERMHEADISFOLLOWEDBYFORMATIONOFTHEFERTILIZATIONCONE4HEFORESTOF MICROVILLICOVERINGTHESURFACEOFTHEOOLEMMAISABSENTFROMTHEFERTILIZATIONCONE!FTERINCORPORATIONOFTHESPERM THECONE RETRACTSANDDISAPPEARS&ROM)WAMATSUAND/HTA B¶REPRODUCEDWITHPERMISSIONOF*OHN7ILEY3ONS )NC

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&IGURE 4RANSMISSION ELECTRON MICROGRAPHS OF THE SPERM ATTACHMENT SITE IN THE EGG OF THE MEDAKA /RYZIAS LATIPES SHORTLYAFTERINSEMINATION&ROM)WAMATSUAND/HTA ¶REPRODUCEDWITHPERMISSIONOF*OHN7ILEY3ONS )NC ! !SPERMATOZOONONTHEVITELLINESURFACE4HESPERMHEADHASBEENCAUGHTBYMICROVILLIOFTHEEGGSECONDSAFTERINSEMI NATION4HEREHASBEENNOFUSIONBETWEENTHEPLASMAMEMBRANESOFTHESPERMANDEGG8 " !SPERMATOZOONSURROUNDEDBYMICROVILLI-6 ANDTHEFERTILIZATIONCONE&#SEEINSET OFTHEEGGSECONDSAFTERINSEM INATION4HESPERMTAIL34 ISTRAPPEDBYMICROVILLI8 4HEREHASBEENNOFUSIONBETWEENTHEIRPLASMAMEMBRANES 8 # !HIGHERMAGNIlCATIONOFTHEPOINTOFCONTACTBETWEENSPERMANDEGGSHOWNIN"4HEREHASBEENNOFUSIONBETWEENTHEIR PLASMAMEMBRANES8 $ !SPERMATOZOONENCLOSEDBYCYTOPLASMICPROTRUSIONSOFTHEEGGMINUTEAFTERINSEMINATION4HEREHASBEENPARTIALFUSION ARROW OFTHEPLASMAMEMBRANESOFTHESPERMANDEGG8

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&IGURE 0HOTOMICROGRAPHS OF A LIVING EGG OF THE MEDAKA /RYZIAS LATIPES SHOWING THE EARLY RESPONSE OF THE ANIMAL POLEREGIONTOSPERMENTRY)NTHESElGURES ABOUTlVEMINUTESHASELAPSEDFOLLOWINGATTACHMENTOFTHESPERMATOZOONTOTHE OOLEMMA"ARM&ROM)WAMATSU REPRODUCEDWITHPERMISSIONFROM"LACKWELL0UBLISHING ! !NEGGWITHTWOSPERMATOZOAINTHEMICROPYLEHASRESPONDEDBYEXOCYTOSISOFCORTICALALVEOLICA AROUNDTHEINNEREND ARROW OFTHEMICROPYLARCANALO OILDROPLET " # 4HESECONDSPERMATOZOONWHITEARROWHEAD HASBEENPUSHEDTOWARDTHEMICROPYLARVESTIBULEBYTHEFERTILIZATIONCONE SURROUNDINGTHElRSTSPERMATOZOON $ & 3UPERNUMERARYSPERMATOZOAWHITEARROWHEADS HAVEBEENSQUEEZEDOUTOFTHEMICROPYLE ' (4HELOWERTHIRDBETWEENARROWS OFTHEMICROPYLARCANALHASCLOSED"LACKARROWHEADSINDICATETHELARGEBLISTER LIKE FERTILIZATIONCONE

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@±± &IGURE 3CANNING ELECTRON MICROGRAPH OF AN EGG FUSED WITH A SPERM HEAD SMALL ARROW AT THE SPERM ENTRY SITE ON THE EGG SURFACE IMMEDIATELY UNDER THE MICROPYLE IN EGGS OF 4RIBOLODON HAKONENSIS 4HE FERTILIZATION CONE LARGEARROW HASRISENFROMTHEREGIONOFTHESITEBENEATHTHE FUSEDSPERMHEAD4HEARROWHEADINDICATESTHESPERMTAIL 8 &ROM+UDO A¶REPRODUCEDWITHPERMISSION OF*OHN7ILEY3ONS )NC

@±± &IGURE 3CANNING ELECTRON MICROGRAPHS SHOWING THE PROCESS OF SPERM ENTRY THROUGH THE MICROPYLES OF INSEMINATED EGGS OF THE ROSE BIT TERLING 2HODEUS OCELLATUS OCELLATUS &ROM /HTA AND .ASHIROZAWA ¶REPRODUCEDWITHPERMISSIONOF*OHN 7ILEY3ONS )NC ! /NE MINUTE AFTER INSEMINATION ! FERTILIZING SPERMATOZOON AR ROW ISVISIBLEATTHESPERMENTRY SITE8 " 4HREEMINUTESAFTERINSEMINATION 4HEFERTILIZINGSPERMATOZOONISNO LONGERVISIBLEANDASWOLLENMASS 3- HAS FORMED AND PLUGS THE MICROPYLE8 # &IVE MINUTES AFTER INSEMINATION 8 $ 4WENTY MINUTES AFTER INSEMINA TION ! SWOLLEN MASS REMAINS PLUGGINGTHEMICROPYLE8

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&IGURE %NGULFMENT OF THE SPERM HEAD IN EGGS OF TILAPIA /REOCHROMIS NILOTICUS IS FOLLOWED BY AN INDENTATION OF THEOOLEMMA THECLEFTOFPENETRATION4HISISASCANNINGELECTRONMICROGRAPHOFTHECLEFTOFPENETRATIONINADECHORIONATEDEGG FOLLOWINGPENETRATIONOFTHESPERMHEADONEMINUTEAFTERINSEMINATION8 4HESPERMTAILREMAINSOUTSIDEINSET8 &ROM"ERNAND!VTALION REPRODUCEDWITHPERMISSIONFROM%LSEVIER3CIENCE

&IGURE 3CANNING ELECTRON MICROGRAPHS SHOWING THE TWO TIERED FERTILIZATION CONE THAT IS FORMED IN THE AYU lSH 0LECOGLOSSUSALTIVELIS4HECHORIONWASDISSECTEDAWAYAFTERlXATION&ROM+UDO BREPRODUCEDWITHPERMISSIONFROM "LACKWELL0UBLISHING ! 4HElRSTFERTILIZATIONCONE&& ISACYLINDRICALSTRUCTURETHATRISESFROMTHESPERMENTRYSITEWITHINSECONDSOFIMMERSION INFRESHWATER8 " !TABOUTSECONDS ASECONDTIERFORMSAPEDESTAL0 ELEVATINGTHElRSTCONE&& FROMITSAPEX4HESPERMTAILISINCLOSE CONTACTWITHTHElRSTFERTILIZATIONCONEARROWS 8

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&IGURE 4RANSMISSIONELECTRONMICROGRAPHSOFSECTIONSOFEGGSOFTHEELKHORNSCULPIN!LCICHTHYSALCICORNISAFTERIM MERSIONINSEAWATER&ROM+OYA 4AKANO AND4AKAHASHI REPRODUCEDWITHPERMISSIONFROMTHE:OOLOGICAL3OCIETYOF *APAN ! "YTENSECONDSAFTERIMMERSIONINSEAWATERAFERTILIZINGSPERMATOZOONHASPENETRATEDTHEOOPLASMANDFUSIONOFTHEMEM BRANESOFTHESPERMANDEGGHASBEGUN3EVERALVESICLESARESEENNEARTHESPERMHEADARROWS 8

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&IGURE #ONTINUED " "Y TWO MINUTES AFTER IMMERSION IN SEA WATER THE SPERM HEAD AND MITOCHONDRIA M HAVE PENETRATED THE OOPLASM 4HEOOPLASMAROUNDTHESPERMFORMSANELECTRON DENSEZONEEDL CONTAININGLYSOSOMES8 # !TTWOMINUTES THEVESICLESARROWS AREARRANGEDINAROWNEARTHESPERMNUCLEUSN 8 $ 4HEMICROTUBULESOFTHESPERMTAILHAVEDEGENERATEDBYSECONDSAFTERIMMERSIONINSEAWATER4HESPERMMITOCHONDRIA M REMAINOUTSIDETHEOOLEMMA8

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&IGURE ! SERIES OF PHOTOMICROGRAPHS OF AN EGG OF THE MEDAKA /RYZIAS LATIPES AT INTERVALS FOLLOWING INSEMINATION !WAVEOFINTRACELLULAR#A RELEASEDBYFERTILIZATION PASSESDOWNTHEEGGFROMTHEMICROPYLEATTHELEFTITISVISUALIZEDBY THE LUMINENSCENCE OF AEQUORIN MICROINJECTED INTO THE EGG "AR M &ROM9OSHIMOTO ET AL REPRODUCED WITH PERMISSIONFROM"LACKWELL0UBLISHING

&IGURE 4HERELEASEOFCALCIUMFROMINTRACELLULARSTORESPRECEDESTHECORTICALREACTIONINOOCYTESOFlSH4HISSCHEME SUGGESTSTHEINVOLVEMENTOFTHEPHOSPHOINOSITIDECASCADE ACOMMONPATHWAYINMANYCELLS"INDINGOFASPERMATOZOONTO ITS RECEPTOR 2S LEADS TO THE ACTIVATION OF PHOSPHOLIPASE # 0,# MEDIATED BY A GUANINE NUCLEOTIDE DEPENDENT REGULATORY PROTEIN'P 0,#CATALYSESBREAKDOWNOFPHOSPHATIDYLINOSITOL BIPHOSPHATE0)0 INTODIACYLGLYCEROL$' ANDINOSITOL TRIPHOSPHATE )0 )0 INTERACTS WITH A SPECIlC RECEPTOR 2I ON CYTOPLASMIC CALCIUM STORES WHICH RELEASES #A TO THE CYTOSOL 4HE CYTOSOLIC #A ACTIVATES 0,# IN TURN FORMING )0 AND $' &ROM )WAMATSU 9OSHIMOTO AND )WAMATSU BREPRODUCEDWITHPERMISSIONFROM%LSEVIER3CIENCE

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&IGURE %LECTRICALCHANGESACCOMPANYINGFERTILIZATIONANDCORTICALVESICLEBREAKDOWNINTHEEGGOFTHEMEDAKA/RY ZIASLATIPES4HEAVERAGERESTINGPOTENTIALACROSSTHEOOLEMMAOFUNFERTILIZEDEGGSIN2INGERSSOLUTIONISnM6 &OLLOWINGFERTILIZATIONARROW THEMEMBRANEDEPOLARIZESOVERAPERIODOFSECBYAFEWMILLIVOLTS4HISISFOLLOWED BYALONGERPHASEOFHYPERPOLARIZATION!STEADYRESTINGPOTENTIALOFnM6ISREACHEDBYMINAFTERFERTILIZATION &ROM.UCCITELLI BREPRODUCEDWITHPERMISSIONFROM%LSEVIER3CIENCE

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&IGURE 4RANSMISSION ELECTRON MICROGRAPHS OF SECTIONS OF THE CORTEX OF EGGS OF THE MEDAKA /RYZIAS LATIPES &ROM )WAMATSUAND+EINO REPRODUCEDWITHPERMISSIONFROM"LACKWELL0UBLISHING ! !CORTICALALVEOLUS#! ANDITSCONTENTS INCLUDINGASPHERICALBODY3" BEFOREBREAKDOWN-ICROVILLIARROWS DECORATE THEOOLEMMA8 " "Y SECONDS AFTER INSEMINATION ONLY EMPTY POCKETS #!0 OPENING INTO THE PERIVITELLINE SPACE 03 REMAIN FROM THECORTICALALVEOLI8

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&IGURE 3CANNINGELECTRONMICROGRAPHOFTHESURFACEOFANEGGOFTHEMEDAKA/RYZIASLATIPESSECONDSAFTERINSEMI NATION*USTBEFOREITSRELEASE ASPHERICALBODYPEEPSTHROUGHALARGEAPERTUREINACORTICALALVEOLUS8 &ROM)WAMATSU AND+EINO REPRODUCEDWITHPERMISSIONFROM"LACKWELL0UBLISHING

&IGURE 3CHEMATIC DRAWINGS SHOWING THE DISTRIBUTION OF COMPACT OOPLASM IN THE CORTICAL LAYER OF THE EGG OF THE CHUMSALMON/NCORHYNCHUSKETADURINGTHEBREAKDOWNOFCORTICALALVEOLI)NTHEINTACTEGGA ACORTICALALVEOLUS#6 AP PROACHESTHEOOLEMMA!SITAPPROACHESB ASMALLAREAOFITSMEMBRANEBECOMESDECORATEDWITHCOMPACTOOPLASM#/ !S THE ALVEOLUS OPENS TO THE PERIVITELLINE SPACE C THE ALVEOLAR MEMBRANE WITH THIS COMPACT OOPLASM INCREASES IN AREA 4HECOMPACTOOPLASMUNITESD WITHTHECORTICALLAYERARROWHEADS 4HEALVEOLARCONTENTS3" ARElNALLYDISCHARGEDE &ROM+OBAYASHI AREPRODUCEDWITHPERMISSIONOFTHE&ACULTYOF3CIENCE (OKKAIDO5NIVERSITY

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&IGURE 4RANSMISSIONELECTRONMICROGRAPHOFASECTIONTHROUGHTHECORTICALLAYEROFTHEANIMALPOLELAYEROFTHEEGGOF THECHUMSALMON/NCORHYNCHUSKETADURINGTHEBREAKDOWNOFACORTICALALVEOLUS!COATINGOFDENSEOOPLASM#/ ENVELOPS THECORTICALALVEOLUSJUSTBEFOREEXPULSIONOFITSCONTENTS#) INTOTHEPERIVITELLINESPACE03 "ARM&ROM+OBAYASHI AREPRODUCEDWITHPERMISSIONOFTHE&ACULTYOF3CIENCE (OKKAIDO5NIVERSITY

&IGURE %LECTRONMICROGRAPHSOFFREEZEFRACTUREREPLICASOFACTIVATEDEGGSOFTHEZEBRAlSH"RACHYDANIORERIOTOILLUSTRATE LATERSTAGESOFCORTICALGRANULAREXOCYTOSIS&ROM(ARTAND#OLLINS REPRODUCEDWITHPERMISSIONFROM3PRINGER 6ERLAG ! %N FACE VIEW OF A WIDE TRANSIENT CRATER LINED WITH A MEMBRANE OF LOW PARTICLE DENSITY REMAINS ON THE SURFACE OF THE SITEOFEXPULSION4HEDIFFERENCEINPARTICLEDENSITYISMAINTAINEDBETWEENTHEDOMAINSOFTHEFORMERCORTICALVESICLEAND THEOOLEMMA8 " 0 FACE REPLICA OF THE SURFACE OF AN EGG MINUTES AFTERACTIVATIONSHOWINGDISTINCT MEMBRANEDOMAINSOFHIGH ( AND LOW, PARTICLEDENSITY8

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&IGURE 4RANSMISSIONELECTRONMICROGRAPHSOFEGGSOFTHEMEDAKA/RYZIASLATIPESSHOWINGSHRINKAGEOFTHEPOCKETS LEFTFROMTHERELEASEOFTHECONTENTSOFCORTICALALVEOLI,ARGENUMBERSOFMICROVILLIMV SPROUTWITHINTHECRATER BEGINNING NEARTHEAPERTURE! " !NELECTRON DENSELAYEROFOOPLASMARROWS SURROUNDSTHECRATER!8 "8 #8 &ROM)WAMATSUAND/HTA REPRODUCEDWITHPERMISSIONFROM3PRINGER 6ERLAG

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&IGURE 3CANNINGELECTRONMICROGRAPHSOFTHESURFACEOFTHEEGGOFTHEZEBRAlSH"RACHYDANIORERIOFOLLOWINGCORTICAL ALVEOLARBREAKDOWN&ROM(ARTAND9U ¶REPRODUCEDWITHPERMISSIONOF*OHN7ILEY3ONS )NC ! !LTHOUGHMOSTEVIDENCEOFEXOCYTOSISHASDISAPPEAREDFROMTHESURFACE TWOMEMBRANEDOMAINSREMAINDISTINCTTHEhPEB BLEDvSURFACELEFTFROMTHEPERIGRANULARMEMBRANEISSURROUNDEDBYTHEhFOLDEDvMEMBRANEDERIVEDFROMTHEOOLEMMA 8 " -EMBRANOUSFOLDSOFTHEOOLEMMASURROUNDTHEPERIGRANULARMEMBRANEPATCH#- ASITISBEINGENVELOPED8 # 4HE PERIGRANULAR MEMBRANE PATCH IS ALMOST COMPLETELY ENVELOPED BY CONVERGING RADIATING FOLDS OF THE OOLEMMA 8

&IGURE 3CANNINGELECTRONMICROGRAPHOFTHESURFACEOFANEGGOF&UNDULUSHETEROCLITUSATSECONDSAFTERINSEMINA TION FOLLOWINGTHECORTICALREACTION4HREADSOFEXCESSMEMBRANEARROWS AREEXPELLEDFROMTHEEMPTYCRATEROFACORTICAL VESICLE8 &ROM"RUMMETTAND$UMONT ¶REPRODUCEDWITHPERMISSIONOF*OHN7ILEY3ONS )NC

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&IGURE )MAGESOFTHEEGGCORTEXOFTHEZEBRAlSH"RACHYDANIORERIO&ROM(ARTAND#OLLINS REPRODUCEDWITH PERMISSIONFROM3PRINGER 6ERLAG ! 0ROlLE VIEW OF A FREEZE FRACTURED VACATED CRYPT OF A CORTICAL ALVEOLUS SHOWING ATTACHED COATED VESICLES ARROWHEADS 8 " 4RANSMISSIONELECTRONMICROGRAPHOFAGRAZINGSECTIONTHROUGHAVACATEDCRYPTOFACORTICALALVEOLUSSHOWINGSEVERALFORM INGCOATEDVESICLES8

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&IGURE #ONTINUED & !FERTILIZEDEGGSIXTOSEVENMINUTESAFTERACTIVATION4HEDISCHARGEDMATERIALFROMTHECORTICALGRANULESTOGETHERWITH THEPERIVITELLINEGLOBULES0' FORMSACOLLOID LIKEHYALINELAYERAROUNDTHEEGG

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&IGURE 4RANSMISSIONELECTRONMICROGRAPHSOFSECTIONSTHROUGHTHECHORIONOFTHECARP#YPRINUSCARPIO&ROM+UDO REPRODUCEDWITHPERMISSIONFROM"LACKWELL0UBLISHING ! !TTHETIMEOFFERTILIZATION THECHORIONISPERFORATEDBYPORECANALSANDCONSISTSOFFOURLAYERS AND4HEPERIVITEL LINESPACEISSEENATTHEBOTTOMOFTHEMICROGRAPH8 " !TTHISTIME THElRSTLAYEROFTHECHORIONCONSISTSOFANINNERELECTRON DENSEREGIONANDANOUTERELECTRON LUCENTPORTION THATISFORMEDFROMMATERIALOOZINGTHROUGHTHEPORECANALS!COLUMNARBARRIER#/ CONSTRICTSTHEPORECANAL PROVIDING ANANCHORPOINTFORTHEOUTERLAYER8 #!FTERMINUTES THElLAMENTOUSOUTERLAYEROFTHECHORIONHASINCREASEDINTHICKNESSBYlVEFOLD8

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&IGURE 3CANNING ELECTRON MICROGRAPHS OF THE SURFACE OF THE CHORION OF EGGS OF THE AYU lSH 0LECOGLOSSUS ALTIVELIS &ROM+UDOAND)NOUE ¶REPRODUCEDWITHPERMISSIONOF*OHN7ILEY3ONS )NC ! !TTHETIMEOFFERTILIZATION THESURFACEISCOVEREDWITHAFAIRLYUNIFORMMESHWORKOFlLAMENTOUSMATERIALEXTENDINGINALL DIRECTIONS8 " 3OMETIMELATER THElLAMENTSHAVEAGGREGATEDINTOREGULARLYSPACEDROUNDMASSES8

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&IGURE 3CANNINGELECTRONMICROGRAPHOFTHEINNEROPENINGOFTHEMICROPYLEINTHEEGGOF&UNDULUSHETEROCLITUS&ROM "RUMMETTAND$UMONT ¶REPRODUCEDWITHPERMISSIONOF*OHN7ILEY3ONS )NC 4HEDIAMETEROFTHECANALPRECLUDES THEADMISSIONOFMORETHANTHESINGLESPERMWHICHCANBESEENABOUTTOEMERGE8

&IGURE 0HOTOMICROGRAPHS BY PHASE CONTRAST OF A LIVING EGG OF THE MEDAKA /RYZIAS LATIPES SHOWING CHANGES IN THE MICROPYLEFOLLOWINGINSEMINATIONAT #!RROWSINDICATESPERMATOZOA8&ROM)WAMATSU )SHIJIMA AND.AKASHIMA ¶REPRODUCEDWITHPERMISSIONOF*OHN7ILEY3ONS )NC ! "EFOREINSEMINATION " SECONDSAFTERATTACHMENTOFSPERMTOTHEOOLEMMA#ONTRACTIONARROWHEADS OFTHEINNERLAYEROFTHECHORIONFOLLOWING DISCHARGEOFTHEALVEOLARCONTENTSRESULTSINTHECLOSUREOFTHEINNERTHIRDOFTHEMICROPYLARCANAL # SECONDS $ SECONDS

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&IGURE 0HOTOMICROGRAPHS OF THE MICROPYLE IN A LIVING EGG OF THE CHUM SALMON /NCORHYNCHUS KETA "AR M &ROM+OBAYASHIAND9AMAMOTO ¶REPRODUCEDWITHPERMISSIONOF*OHN7ILEY3ONS )NC ! 4HEUNFERTILIZEDEGG4HEMICROPYLEISINDICATEDBYANARROW " )MMEDIATELYAFTERINSEMINATION # 3EVENMINUTESAFTERINSEMINATIONSHOWINGTHEDISCHARGEOFSUPERNUMERARYSPERMATOZOA33 FROMTHEMICROPYLARCANAL

&IGURE 3CANNINGELECTRONMICROGRAPHSOFTHEMICROPYLARAPERTUREINEGGSOFTHEMEDAKA/RYZIASLATIPESBEFOREAND AFTERINSEMINATION&ROM)WAMATSUETAL REPRODUCEDWITHPERMISSIONFROM"LACKWELL0UBLISHING ! 4HEARROWINDICATESTHEMICROPYLEOFANUNFERTILIZEDEGG"ARM " 4HISMICROPYLEISSHOWNATAHIGHERMAGNIlCATION"ARM # $6ITELLINEmUIDHASEXUDEDFROMTHEMICROPYLEBYSECONDSAFTERSPERMATTACHTOTHEEGG"ARM

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&IGURE 4RANSMISSIONELECTRONMICROGRAPHSOFSECTIONSTHROUGHTHEMICROPYLESOFINSEMINATEDEGGSOFTHECOMMONCARP #YPRINUSCARPIO&ROM+UDO REPRODUCEDWITHPERMISSIONFROM"LACKWELL0UBLISHING ! 4HE FERTILIZATION CONE HAS GROWN AS FAR AS THE MICROPYLAR VESTIBULE AND PLUGS THE MICROPYLAR CANAL! SPERM HEAD IS EMBEDDEDATTHEBASEOFTHEFERTILIZATIONCONEITSTAILLIESALONGSIDETHECONE8 " 4HREESECTIONSOFASINGLEFERTILIZATIONCONECONTAININGTHElRSTSPERMNUCLEUS3. 3EVERALSPERMATOZOA DENIEDACCESSBY THEFERTILIZATIONCONE ARECLUSTEREDINTHEMICROPYLARCANAL8

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&IGURE 3CANNING ELECTRON MICROGRAPHS OF THE SURFACE OF INSEMINATED EGGS OF THE PADDLElSH 0OLYODON SPATHULA ONE MINUTEAFTERFERTILIZATION4HEPADDLElSHPRODUCESANEGGWITHMULTIPLEMICROPYLES&ROM,INHARTAND+UDO REPRODUCED WITHPERMISSIONFROM%LSEVIER3CIENCE ! 4HEBALL SHAPEDENDOFAFULLYDEVELOPEDFERTILIZATIONCONEEXTENDSFROMTHEEXTERNALAPERTUREOFAMICROPYLE8 " /NEOFTHEMICROPYLARCANALSINTHEMICROPYLARAREAOFTHECHORIONISSEALEDWITHAFULLYGROWNCONELARGEARROW THEOTHERS ARROWHEADS APPEARTOBEBLOCKEDTOVARIOUSDEGREESWITHOTHERMATERIALS PROBABLYEXUDATESFROMTHECORTICALALVEOLI !SPERMTAILEXTENDSFROMAPOREOFONEOFTHEMICROPYLARCANALSSMALLARROW 8

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&IGURE 4RANSMISSION ELECTRON MICROGRAPHS OF SECTIONS THROUGH THE EPITHELIUM OF OVARIAN DUCTS OF THE PLATYlSH 8IPHOPHORUSMACULATUS&ROM0OTTERAND+RAMER ¶REPRODUCEDWITHPERMISSIONOF*OHN7ILEY3ONS )NC ! #OMPLEXINFOLDINGSARROWHEADS PENETRATEDEEPBETWEENTHESEEPITHELIALCELLSOFTHEOVARIANDUCT!PICALTIGHTJUNCTIONS ARROWS ANDDESMOSOMESCURVEDARROWS AREAPPARENT!SPERMNUCLEUS3. ISINCORPORATEDWITHINASPERM ASSOCIATED CELL8 " 4HESESPERM ASSOCIATEDCELLSEXHIBITDEEPSURFACEPITSANDPOCKETS)NTACTSPERMNUCLEI3. WITHMIDPIECEMITOCHONDRIA - ANDmAGELLAARROWHEADS ARESEENWITHINTHEPOCKETS/$, LUMENOFTHEOVARIANDUCT8

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&IGURE 4RANSMISSION ELECTRON MICROGRAPHS OF SECTIONS OF THE WALL OF THE EGG CAPSULE OF THE DOGlSH 3CYLIORHINUS CANICULA 4HE WALL IS A COMPOSITE MATERIAL CONSTRUCTED LARGELY OF COLLAGEN lBRES WITH A HIGHLY ORDERED KINKED MOLECULAR ARRAGEMENTSETINAMATRIXCONTAININGHYDROPHOBICSPHERICALlLLERPARTICLESMINDIAMETER8 &ROM+NIGHTAND &ENG AREPRODUCEDWITHPERMISSIONFROM%LSEVIER3CIENCE ! 4HEOUTERMOSTLAYER, OFTHEEGGCAPSULESHOWINGHYDROPHOBICGRANULES$ 3OMEREPEATSOFTHEAXIALPERIODOF THElNElBRILLARPHASEOFTHECOLLAGENCANBESEENBETWEENTHETWOGRANULES " !SIN!!HYDROPHOBICGRANULEAPPEARSTOLIEBETWEENTWOSEGMENTSOFTHElNALlBRILLARPHASE4HEBROADLUCENTBAND OFTHEBANDINGPATTERNAPPEARSTORUNALLTHEWAYAROUNDTHEGRANULE SUGGESTINGTHATITISCOATEDWITHACOMPLETELAYEROF COLLAGENMOLECULES

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&IGURE -ICROGRAPHS OF THE OVIDUCTAL GLAND OF THE DOGlSH 3CYLIORHINUS CANICULA &ROM +NIGHT AND &ENG REPRODUCEDWITHPERMISSIONFROM+LUWER!CADEMIC0LENUM0UBLISHER ! 3CANNING ELECTRON MICROGRAPH LOOKING DOWN INTO TWO % ZONE TRANSVERSE GROOVES WHICH RUN VERTICALLY UP THIS lGURE 4HESPINNERETSINTHEBOTTOMOFTHEGROOVECONSISTOFAREGULARARRANGEMENTOFBAFmEPLATES4HESMALLARROWINDICATES THEOBLIQUESPACEBETWEENTWOBAFmEPLATESTHELARGEARROWPOINTSTOTHESPACEBETWEENTHEPOSTERIORSURFACEOFTHEBAFmE PLATEANDTHEWALLOFTHETRANSVERSEGROOVE3CALEBARM " 0HOTOMICROGRAPH OF A SECTION OF THE OVIDUCTAL GLAND SHOWING THE $ ZONE GROOVES BROAD ARROW BAFmE PLATES NARROW ARROW SECRETORYDUCTS ANDGLANDTUBULESWHITEARROW 3CALEBARM

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HAS THE MOTHER LAID DOWN YOLK DURING VITELLOGENESIS BUTSHESUPPLIESADDITIONALNUTRIENTSDURINGEMBRYONIC DEVELOPMENT7ITHTHEESTABLISHMENTOFMATROTROPHY VARIOUSELABORATESTRUCTURESHAVEEVOLVED ALWAYSFROM PREEXISTING STRUCTURES THAT FACILITATE NUTRIENT TRANSFER DURINGGESTATION'ROVEAND7OURMS 4HIS TRANSFER OF NUTRIENTS IS ACHIEVED IN SEVERAL WAYS 7OURMS 'ROVE AND ,OMBARDI )N THE SIMPLEST TERMED EITHER //0(!'9 OR !$%,0(/0(!'9 SOMEEMBRYOSOFTHEBROODPREYONTHEIRSIBLINGS EI THER AS EGGS OR AS EMBRYOS -ORE ADVANCED TRANSFER ISBYWAYOF 42/0(/$%2-9 WHERERICHLYVASCULARIZED ELABORATIONSOFMATERNALANDEMBRYONICEPITHELIA AL THOUGHNOTININTIMATEASSOCIATION FACILITATEEXCHANGE ACROSS INTERTISSUE SPACES )N A THIRD TYPE OF MATROP ROPHICADAPTATION 0,!#%.4/42/0(9 MATERNALNUTRIENTS ARE TRANSFERRED TO THE EMBRYO BY WAY OF A 0,!#%.4! WHICH MAY BE DElNED AS THE INTIMATE APPOSITION OR FUSIONOFMATERNALANDFOETALORGANSFORPHYSIOLOGICAL EXCHANGE /NE TYPE OF PLACENTOTROPHY IS FOUND ONLY INSHARKSTHE 9/,+ 3!# 0,!#%.4! WHICHCONSISTSOFA MODIlEDYOLKSACCLOSELYAPPOSEDTOTHEUTERINEEPI THELIUM4HISSTRUCTUREFUNCTIONSINTHEABSORPTIONOF YOLKDURINGEARLYGESTATIONLATERITBECOMESMODIlED ASTHEFOETALPORTIONOFTHEPLACENTA/THERPLACENTAL RELATIONSHIPS HAVE BEEN CITED INCLUDING THE &/,,)#5 ,!2 0,!#%.4! AN INTIMATE ASSOCIATION BETWEEN THE FOLLICULAR WALL AND EMBRYONIC SURFACES "5##!, !.$ "2!.#()!,0,!#%.4!3WHERERICHLYVASCULAREXTENSIONS OFMATERNALTISSUEGROWINTOTHEFOREGUTOFTHEFOETUS ANDTHE 42/0(/4!%.)!, 0,!#%.4!WHEREELABORATEOUT GROWTHS OF THE HINDGUT OF THE FOETUS THE 42/0(/4!% .)!% ABSORBNUTRIENTSPROVIDEDBYTHEOVARIANLUMINAL EPITHELIUM )TISOFTENDIFlCULTNOTTOOVERSTEPTHELINESEPARAT INGTHEREALMSOFHISTOLOGYANDEMBRYOLOGYTHISDIS TINCTIONBECOMESESPECIALLYTENUOUSINADISCUSSIONOF VIVIPARITY&ORTHEMOSTPART DEVELOPMENTALCONSIDER ATIONSHAVEBEENOMITTEDFROMTHEPRESENTWORKEXCEPT WHERE THEY MAY CAST LIGHT ON THE NATURE OF A MATURE

)NTRODUCTION

6IVIPARITYISAPROCESSINWHICHEGGSAREFERTILIZEDIN TERNALLYANDUNDERGODEVELOPMENTWITHINTHEMATERNAL REPRODUCTIVE SYSTEM 7OURMS 'ROVE AND ,OMBAR DI !LTHOUGH MOST lSHES ARE OVIPAROUS FAMILIESOFLIVINGlSHESHAVESPECIESTHATBEARLIVING YOUNGTHESEINCLUDEFAMILIESOFCHONDRICHTHYANS THE SINGLE COELACANTH ,ATIMERIA CHALUMNAE AND FAMILIESOFTELEOSTS7HILEASMANYASOFTO SPECIES OF CHONDRICHTHYANS PRACTICE VIVIPARITY ONLY OF AN ESTIMATED SPECIES OF TELEOSTS DOSO/NEEXPLANATIONFORTHISDISPARITYMAYBETHAT TELEOSTSLACK-àLLERIANDUCTSWHICHAREUSEDASBROOD CHAMBERSINOTHERVIVIPAROUSVERTEBRATES7AKE 3CHINDLERAND(AMLETT 4HETELEOSTS HOWEVER HAVESHOWNGREATRESOURCEFULNESSINMAKINGOTHERAR RANGEMENTS FOR THE INTERNAL CARE OF THEIR YOUNG AND GESTATIONOCCURSWITHINTHEOVARYITSELF )NTHEEVOLUTIONOFVIVIPARITY THEREHASBEENATEN DENCYAWAYFROMADEPENDENCYOFTHEEMBRYOONITS OWN YOLK RESERVES TO A GREATER RELIANCE ON NUTRIENTS SUPPLIEDBYTHEMOTHER THEREBYESTABLISHINGTHEDIS TINCTIONBETWEEN ,%#)4(/42/0(9AND -!42/42/0(9)N LECITHOTROPHY LITTLEORNONUTRIENTMATERIALCROSSESTO THEEMBRYOFROMTHEMATERNALCIRCULATIONANDALL OR NEARLY ALL OF THE SUBSTRATES FOR GROWTH AND METABO LISMAREOBTAINEDFROMYOLKRESERVESSTOREDINTHEEGG PRIORTOFERTILIZATION'ROVEAND7OURMS (OLLENBERG AND 7OURMS $URING GESTATION LECITHOTROPHICEMBRYOSUNDERGOALOSSINWEIGHTOFOR GANICMATERIALSIMILARTOTHATWHICHTAKESPLACEDURING THEDEVELOPMENTOFOVIPAROUSlSHES)NMATROTROPHY HOWEVER YOLKRESERVESARESUPPLEMENTEDDURINGGES TATIONBYMATERIALSPROVIDEDBYTHEMOTHERNOTONLY

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A'OLGICOMPLEXWITHASSOCIATEDPOPULATIONSOFCOAT EDANDUNCOATEDVESICLES ANDCONSPICUOUSLIPID LIKE INCLUSIONS&IGURES" # 4HEREISNOEVIDENCEOF PINOCYTOTIC ACTIVITY4HIS EPITHELIUM RESTS ON A BASAL LAMINABELOWWHICHISACOLLAGENOUSSTROMACONTAIN INGDENSESPHERICALINCLUSIONS&IGURE$ 4HEINNERREGIONSOFTHEYOLKSACCOMPRISETHESO MATICMESODERM ANINTERVENINGNARROWEXTRAEMBRY ONIC COELOM AND THE SPLANCHNIC MESODERM VITELLINE CAPILLARY REGION &IGURE 7OURMS 'ROVE AND ,OMBARDI 4HE STRUCTURE OF THE SOMATIC AND SPLANCHNICMESODERMISSIMILARTOTHATOFCLASSICME SOTHELIUM CONSISTING OF A SINGLE LAYER OF SQUAMOUS CELLSLYINGONVASCULAR AREOLARCONNECTIVETISSUE-E SOTHELIAL CELLS HAVE mATTENED NUCLEI LONGITUDINAL CY TOPLASMIClBRILS SMOOTH WALLEDANDCOATEDVESICLES AND DENSE MEMBRANE BOUND GRANULES 3URFACES OF ADJACENTCELLSINTERDIGITATEBUTSHOWFEWDESMOSOMES 9OLK SAC CAPILLARIES LINED BY CONTINUOUS ENDOTHE LIUM AREADJACENTTOTHEINNERSURFACEOFTHESPLANCH NICMESODERMALLAYER!BUNDANTENDOCYTOTICACTIVITY INMESOTHELIALANDENDOTHELIALEPITHELIAINDICATESTHE OCCURRENCEOFVESICULARTRANSPORT PRESUMABLYOFMA TERIALS DERIVED FROM YOLK BREAKDOWN 4HE ENDODERM ISINCLOSECONTACTWITHTHEBASALLAMINAOFTHECAPIL LARYENDOTHELIUM)TSCELLSCONTAINMANYMITOCHONDRIA AND POLYRIBOSOMES HETEROGENEOUS SMOOTH WALLED VESICLES ANDMANYYOLKDEGRADATIONVESICLES&IGURE ! 4HEINNERMOSTLAYER THEYOLKSYNCYTIALLAYER CONTAINSMANYHETEROGENEOUSYOLKGRANULESINVARIOUS STAGESOFDEGENERATION&IGURES" # !SYOLKRESERVESAREDEPLETED THEUTERINEEPITHELIUM SECRETES HISTOTROPH THAT BATHES THE EMBRYO (AMLETT )N MOST SHARKS THE EMBRYO IS STILL CONTAINED WITHIN ITS EGG CAPSULE &IGURE 4HE CAPSULE IS MTHICKINTHESHARK-USTELUSCANISANDCONSISTS OFFOURORMOREORTHOGONALLY ARRANGEDLAMINAEOFl BROUS MATERIAL &IGURE ,OMBARDI AND &ILES 4HE OUTER LAMINA IS TIGHTLY CONSTRUCTED WITH NO VISIBLE PORES GREATER THAN NM IN DIAMETER 4HE CAPSULE IS PERMEABLE TO MATERIALS BELOW A MO LECULARWEIGHTOFK$ASOTHATUREAANDGLUCOSECROSS READILY)TISSUGGESTEDTHATTHEEGGCAPSULEASSISTSIN THE ESTABLISHMENT AND MAINTENANCE OF THE PLACENTAL ATTACHMENT BY ACTING AS A SEMIPERMEABLE MEMBRANE BETWEEN THE INTRACAPSULAR AND EXTRACAPSULAR COM PARTMENTS )N THIS SCHEME THE FOETUS RELEASES SOL UTES OF HIGH MOLECULAR WEIGHT DRAWING WATER FROM THEEXTRACAPSULARmUIDS ACROSSTHEEGGCAPSULE INTO THECAPSULARCOMPARTMENT&IGURE 4HERESULTING

DISTENTIONOFTHEEGGCAPSULEEVENTUALLYOBLITERATESTHE EXTRACAPSULARSPACE APPOSINGTHEYOLKSACEGGCAPSULE COMPLEXAGAINSTTHEUTERINELINING THEREBYPERMITTING THESUBSEQUENTINTERDIGITATIONOFMATERNALANDEMBRY ONICTISSUESINTHEFORMATIONOFTHEYOLKSACPLACENTA &IGURE !ROUNDTHETIMEOFIMPLANTATION WHENTHEYOLKIS CONSUMED THEYOLKSAC ESPECIALLYTHEPROXIMALPOR TION BECOMES A HOLLOW SPHERICAL BAG SUPPORTED BY RICHLYVASCULARCONNECTIVETISSUELINKEDTOTHEVITELLINE ARTERYANDVEIN7OURMS 'ROVE AND,OMBARDI #ASTROAND7OURMS )NCREASEDRAMIlCATIONOF THESE VESSELS IN THE DISTAL RUGOSE PLACENTA COMBINED WITH SURFACE FOLDING AND CONNECTIVE TISSUE HYPERPLA SIA GIVE THIS REGION ITS SPONGY TEXTURE )NITIALLY THE MATERNAL PORTION OF THE PLACENTA CONTAINS ALL OF THE CELL LAYERS THAT ARE PRESENT AT NONATTACHMENT SITES !LTHOUGHVARYINGDEGREESOFINTERDIGITATIONANDFUSION OF MATERNAL AND FOETAL TISSUES ENHANCE THE EXCHANGE OF MATERIALS THE SELACHIAN PLACENTA IS CONSIDERED TO BE ./. ).6!3)6% AND ./. $%#)$5!4% SO THAT MATERNAL ANDFOETALTISSUESCANBESEPARATEDWITHOUTDETACHING UTERINETISSUE(AMLETT 7OURMS AND(UDSON C (AMLETT 4HEREISNOBLEEDINGNORSHEDDINGOF MATERNALTISSUEATPARTURITION !S THE FOETUS IMPLANTS THE YOLK STALK ELONGATES 'ILBERTAND3CHLERNITZAUER (AMLETT 7OURMS AND(UDSON A7OURMS 'ROVE AND,OMBARDI (AMLETT (AMLETT -IGLINO AND $IDIO 7HEN THE YOLK SAC mATTENS ITSELF AGAINST THE UTERINEWALLTOFORMTHEFOETALPORTIONOFTHEPLACEN TA THE YOLK STALK IS DESIGNATED THE 5-"),)#!, 34!,+ IT CONTAINS THE MUSCULAR UMBILICAL ARTERY UMBILICAL VEIN THEDUCTUSVITELLO INTESTINALIS AND INMOSTSPE CIES AREMNANTOFTHEEXTRAEMBRYONICCOELOM&IGURE 4HEYOLKSACBECOMESREGIONALLYMODIlEDINTO TWODISTINCTREGIONSTHEDIAPHANOUS02/8)-!,3-//4( 3%'-%.4 IS CONFLUENT WITH THE UMBILICAL STALK AND DRAPESOVERTHERICHLYVASCULAR $)34!, 25'/3% 0/24)/. THAT ABUTS THE UTERINE ATTACHMENT SITE &IGURES AND )NCREASED VASCULARIZATION OF THE YOLK SAC IS REmECTED AT THE POINT OF CONTACT BY ENHANCED VAS CULARIZATION OF THE UTERINE WALL!DJACENT REGIONS OF THE UTERUS DIFFERENTIATE INTO 0!2!0,!#%.4!, 3)4%3 THAT PRODUCEMUCUS&IGURE 4HEJUNCTIONOFTHEVAS CULARIZEDYOLKSACANDUTERINEWALLISTHESITEATWHICH THE EMBRYO WILL IMPLANT AND THE 0,!#%.4! WILL BE FORMED4HEPLACENTACONSISTSOFTHE !44!#(-%.4 3)4% ONTHEUTERINEWALL THEEGGCAPSULEINMOSTSPECIES ANDTHEmATTENED VASCULARPADOFTHEFOETALYOLKSAC

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4HEFOETALPORTIONOFTHEPLACENTAINCLUDESTHEUMBILI CALCORD THESMOOTHPROXIMALPORTION THERICHLYVASCU LARRUGOSEDISTALPORTION ANDTHEEGGCAPSULE&IGURES AND 4HERE ARE NO NOTICEABLE DIFFERENCES INTHESTRUCTUREFROMREGIONTOREGIONOFTHEYOLKSAC PLACENTAPRIORTOIMPLANTATION(AMLETTAND7OURMS (AMLETT (AMLETTETAL A )N THE (!%-!42/0()# NUTRITION OF PLACENTAL SHARKS MATERIALS ARE TRANSFERRED FROM THE BLOOD IN MATERNAL CAPILLARIESOFTHEUTERINEWALLTOFOETALCAPILLARIESINTHE RUGOSE DISTAL PORTION OF THE PLACENTA 3CHLERNITZAUER AND'ILBERT 4ESHIMA (AMLETT 7OURMS AND (UDSON A C 7OURMS 'ROVE AND ,OM BARDI (AMLETTETAL A &OETALCAPILLARIES ARE BETTER DEVELOPED THAN MATERNAL ONES IN -USTELUS GRISEUS THEREBY FACILITATING THE EXCHANGE OF MATERI ALS4ESHIMA )NADDITION FOETALHAEMOGLOBIN OF 3QUALUS SUCKLEYI HAS A GREATER AFlNITY FOR OXYGEN THANADULTHAEMOGLOBIN THEREBYOPTIMIZINGTHETRANS FER OF OXYGEN FROM MATERNAL TO FOETAL CIRCULATION -ANWELL 4HEBARRIERSTOTHEEXCHANGEOFMATERIALSAREMA TERNALENDOTHELIUM MATERNALEPITHELIUM EGGCAPSULE FOETAL EPITHELIUM AND FOETAL ENDOTHELIUM &IGURE )NDIFFERENTCLASSESOFPLACENTAS THEREMAYBEA REDUCTIONINTHESEBARRIERSANDANINCREASEINTHEAREA OF TISSUE CONTACT BY MEANS OF INTERDIGITATION &IGURE )N SOME SHARKS THE NUMBER AND THICKNESS OF LAYERSOFCELLSANDEXTRACELLULARMATRIXMAYBEDIMIN ISHED4HEMATERNALANDFOETALEPITHELIAMAYDEGENER ATE PERMITTINGEACHOFTHECAPILLARYNETWORKSTOABUT ITSOWNSIDEOFTHEEGGCAPSULEATTHEMATERNAL FOETAL PLACENTALJUNCTION4HEEMBRYONICCOELOMWITHINTHE PLACENTAMAYBEOBLITERATEDBYFUSION4HEROLEOFTHE EGGCAPSULEASAPOSSIBLEBARRIERTOPLACENTALTRANSPORT IS ENIGMATIC SINCE LITTLE IS KNOWN OF ITS PERMEABIL ITY7OURMS 'ROVE AND,OMBARDI ,OMBARDI AND&ILES )TISPRESUMEDTHATITSPERMEABILITY IN VIVIPAROUS SPECIES IS ENHANCED BY A REDUCTION IN THICKNESS AND THE POSSIBLE LOSS OR MACROMOLECULAR REARRANGEMENTOFCOLLAGEN!LTHOUGHITISAPOTENTIAL PERMEABILITYBARRIER THEEGGCAPSULEAPPEARSTOPERMIT THEREADYPASSAGEOFSMALLMOLECULESBUTMAYHINDER PASSAGE OF MACROMOLECULES )N SOME SPECIES THERE MAYBENOEGGCAPSULE $URING EARLY GESTATION IN THE !TLANTIC SHARPNOSE SHARK 2HIZOPRIONODON TERRAENOVAE THE UTERINE WALL CONSISTS OF A SIMPLE CUBOIDAL EPITHELIUM RESTING ON A LAYER OF VASCULAR LOOSE AREOLAR TISSUE CONTAINING STRANDS OF LONGITUDINAL SMOOTH MUSCLE &IGURE

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TUREOFTHEUTERINEEPITHELIUMINDICATESGREATACTIVITY IN THE TRANSPORT OF MATERIALS BETWEEN THE RICH BLOOD SUPPLYANDLUMINALSURFACE INCLUDINGFEATURESSUCHAS THETIGHTJUNCTIONSSEALINGTHELUMINALBORDERS ELABO RATEFOLDINGANDINTERDIGITATIONOFLATERALCELLBOUND ARIES BRANCHEDMICROVILLI ANDSACCULARINVAGINATIONS OF THE APICAL SURFACE THE PRESENCE OF APICAL COATED PITSANDNUMEROUSCOATEDVESICLESPROBABLYINDICATES THETRANSFEROFSERUMPROTEINSTOTHEEMBRYO&IGURES # $ 4HE UTERINE EPITHELIAL CELLS ALSO CONTAIN LIPID LIKE INCLUSIONS A PROMINENT GRANULAR ENDOPLAS MICRETICULUM ANDMANYFREERIBOSOMES4HEENDOTHE LIUMOFTHEUTERINECAPILLARIESISPINOCYTOTICALLYACTIVE AND THERE IS LITTLE DISTANCE TO IMPEDE mOW BETWEEN THEEPITHELIALCELLSANDTHECAPILLARIESNORISASIGNIl CANTBARRIERPRESENTEDBYTHEIRTHINBASALLAMINASAND SPARSEINTERVENINGCONNECTIVETISSUE)NADDITIONTOTHE TRANSPORT OF MATERNAL SERUM PROTEINS GASES WASTES AND POSSIBLY IMMUNOGLOBULINS THE ATTACHMENT SITES PROBABLYREGULATEWATER ELECTROLYTES ANDOSMOREGULA TORYFACTORS 4HE 25'/3% $)34!, 0/24)/. OF THE PLACENTA OF # PLUMBEUS CONSISTS OF A SIMPLE COLUMNAR 352&!#% %0)4(%,)5-OFPEG LIKECELLSDERIVEDFROMTHEECTODERM &IGURES ! " A COLLAGENOUS 342/-! CONTAINING VITELLINECAPILLARIES ANDANINNERMOST "/5.$!29 #%,, ,!9%2&IGURE+ (AMLETT 7OURMS AND(UDSON A 4HEEGGCAPSULElTSCLOSELYAROUNDTHESURFACE EPITHELIUM &IGURE # 4HE ULTRASTRUCTURE OF THIS REGIONBEARSWITNESSTOITSHAEMOTROPHICFUNCTIONTHE SURFACEEPITHELIALCELLSARECLOSELYAPPOSEDTOTHEABUN DANTCAPILLARIESOFTHEVITELLINECIRCULATIONANDGIVETHE APPEARANCE OF ACTIVE ABSORPTION WITH THEIR EXTENSIVE APICAL SYSTEM OF SMOOTH WALLED MEMBRANOUS ANAS TOMOSING CANALICULI AND TUBULES &IGURES $ % !CTIVE ENDOCYTOTIC UPTAKE OF THE TRACER HORSERADISH PEROXIDASE HAS BEEN DEMONSTRATED IN THE EPITHELIAL CELLSOFTHEDISTALPLACENTABUTNOTBYTHEEPITHELIUMOF THESMOOTHPORTIONNORBYTHEUMBILICALCORD7HORL LIKE INCLUSIONS IN THE BASAL CYTOPLASM OF THE SURFACE EPITHELIALCELLSLIEADJACENTTOTHEPINOCYTOTICALLYAC TIVE ENDOTHELIUM OF THE CAPILLARIES AND ARE ASSUMED TOBEYOLKPROTEINSBEINGTRANSFERREDFROMTHEMOTHER TOTHEEMBRYOTHROUGHOUTGESTATION&IGURES&TO ) PRESUMABLYTHESAMEYOLKPROTEINPRECURSORSTHAT AREINVOLVEDINOOCYTEGROWTHCONTINUETOBEPRODUCED BYTHEMATERNALLIVERANDAREUSEDASNUTRIENTSFORTHE DEVELOPINGEMBRYOAFTERITHASEXHAUSTEDITSORIGINAL SUPPLYOFYOLK!LLABSORPTIVEACTIVITYOFTHEYOLKSAC APPEARSTOHAVEBEENASSUMEDBYTHEEPITHELIALCELLS

OF THE ECTODERMAL SURFACE WHILE THE FORMERLY ACTIVE ENDODERMAL CELLS FORM A SUPPORTIVE "/5.$!29 ,!9%2 WITHSCANTMICROVILLIANDSPARSEORGANELLESEXCEPTFOR AFEWMITOCHONDRIA&IGURE* !WELLDEVELOPED COLLAGENOUSSTROMASEPARATESTHETWOEPITHELIA 4HE3-//4(02/8)-!,3%'-%.4OFTHESHARKPLACENTA DOESNOTCOMEINTOCONTACTWITHTHEUTERINELININGBUT ISOLATESTHEATTACHMENTSITEBYDRAPINGOVERTHEDISTAL PORTION OF THE PLACENTA SO THAT LITTLE OF IT IS EXPOSED TO THE PERIFOETAL COMPARTMENT CONTAINED WITHIN THE EGGCAPSULE(AMLETT 7OURMSAND(UDSON B 4HE PROXIMAL SEGMENT OF # PLUMBEUS CONSISTS OF OUTER %#4/$%2-!, %0)4(%,)5- AN INTERVENING COL LAGENOUS 342/-! AND THE INNER -%3/4(%,)5- &IGURE * 0RESUMABLY WITH THE DISAPPEARANCE OF THE YOLK THEENDODERMALEPITHELIUMHASWITHDRAWNFROM THE YOLK SAC #APILLARIES ARE SPARSE IN THE STROMA 4HE SURFACE EPITHELIUM BEARS A PROMINENT GLYCOCA LYX )T MAY BE ONE TO THREE CELLS THICK AND CONTAINS TWO CELL TYPES &IGURES ! " # $ & 'OLGI COM PLEXESANDELEMENTSOFENDOPLASMICRETICULUMARERARE IN BOTH EPITHELIAL CELL TYPES AND THERE ARE FEW OF THE ORGANELLES CHARACTERISTIC OF CELLS ENGAGED IN SYNTHET IC ACTIVITY #UBOIDAL CELLS PREDOMINATE THESE HAVE A DOME LIKEAPICALSURFACECOVEREDWITHMICROVILLIAND AN OVOID NUCLEUS4HE SECOND TYPE HAS A CONVOLUTED NUCLEUSANDAmATTENEDAPEXWITHMICROVILLANDCILIA &IGURES # $ ' -ICROPLICAE OCCUR ON THE SUR FACES OF A FEW CELLS "OTH TYPES CONTAIN LIPID INCLU SIONS MANYCYTOPLASMIClLAMENTS ANDAREJOINEDBY DESMOSOMES &IGURE % %PITHELIAL CELLS OF THE MIDDLELAYERAREJOINEDBYDESMOSOMESANDARESIMI LARTOTHOSEOFTHESURFACEEXCEPTTHATTHEYLACKMICRO VILLIANDCILIA4HEINNERMOSTEPITHELIALCELLSPOSSESS ANUNDULATINGBASALCONTOURANDRESTONACONSPICUOUS BASAL LAMINA -ESOTHELIAL CELLS ARE SQUAMOUS WITH A FUSIFORM NUCLEUS MANY SMOOTH WALLED PINOCYTOTIC PITS TRANSPORTVESICLES MITOCHONDRIA FREERIBOSOMES AND A LARGE NUMBER OF CYTOPLASMIC lLAMENTS &IG URES( ) 4HEENDOPLASMICRETICULUM EXCEPTFOR A FEW PATCHES OF THE GRANULAR TYPE AND 'OLGI COM PLEXES ARE POORLY DEVELOPED 4HE MESOTHELIAL CELLS REST ON A PROMINENT BASAL LAMINA THAT SEPARATES THEM FROMTHECONNECTIVETISSUESTROMA4HEFUNCTIONOFTHE PROXIMAL PORTION OF THE PLACENTA IS ENIGMATIC BUT THE PRESENCEOFWELLDEVELOPEDCOLLAGENOUSTISSUE ASWELL AS ABUNDANT DESMOSOMES AND CYTOPLASMIC lLAMENTS WITHINTHEEPITHELIALANDMESOTHELIALCELLS SUGGESTSTHAT IT MAY RESIST MECHANICAL STRESS 4HE NUMEROUS PINO CYTOTICPITSANDVESICLESINTHEMESOTHELIALCELLSMAY

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INDICATEmUIDEXCHANGEBETWEENTHECAVITYOFTHEPLA CENTAANDTHEPERIFOETALCOMPARTMENTWITHINTHEEGG CAPSULE3TRUCTURESCHARACTERISTICOFSTEROIDSECRETION HAVEBEENDESCRIBEDINTHESIMPLECUBOIDALEPITHELIUM OF THE SMOOTH PROXIMAL SEGMENT OF THE YOLK SAC OF 2HIZOPRIONODON TERRAENOVAE MITOCHONDRIA WITH TU BULAR CRISTAE AGRANULAR ENDOPLASMIC RETICULUM AND EXTENSIVE LAMELLAR BODIES &IGURE (AMLETT )TISSUGGESTEDTHATTHESECELLSMAYBEASOURCE OFOESTRADIOLANDTESTOSTERONE 5MBILICAL STALKS OF MOST SPECIES OF #ARCHARHINUS ARE SMOOTH AND THEIR SQUAMOUS EPITHELIUM APPEARS NOT TO BE PERMEABLE TO THE mUIDS WITHIN THE UTERUS )N MANY SELACHIANS HOWEVER THE STALK IS FESTOONED WITHARBORESCENT RICHLYVASCULAR ABSORPTIVEPROCESSES CALLED !00%.$)#5,!% &IGURES TO (AMLETT 7OURMS 'ROVE AND ,OM BARDI #ASTROAND7OURMS (AMLETTETAL A 4HESEOUTGROWTHSMAYBEOFVARIOUSSHAPES mATTENED OR CYLINDRICAL lNGER LIKE OR CLUB SHAPED SOMETIMES BRANCHING !FTER PLACENTATION HAS OC CURRED ITHASBEENSUGGESTEDTHATTHEPLACENTALUTERINE WALL CONTINUES TO SECRETE HISTOTROPH UNTIL PARTURITION ALTHOUGH PERHAPS ONLYINSPECIESTHATPOSSESSAPPEN DICULAE(AMLETT !PPENDICULAE OF 2 TERRAENOVAE FORM VASCULAR LOBED PROTRUSIONS FROM THE UMBILICAL CORD (AMLETT (AMLETT ET AL A B &IGURE ! 4HEY ARECOVEREDWITHCONTINUATIONSOFTHESURFACEEPITHE LIUMOFTHESTALKANDENCLOSEACOREOFRICHLYVASCULAR AREOLAR CONNECTIVE TISSUE4HE EPITHELIUM CONSISTS OF -)#2/6),,!2 AND '2!.5,!2 #%,,3 SUBTENDED BY FLAT TENED "!3!, #%,,3 &IGURES # $ ' -ICROVILLAR CELLS BRISTLING WITH LONG MICROVILLI FORM PYRIFORM PROCESSES THAT ARE INSINUATED BETWEEN ADJACENT CELLS THEIR CYTOPLASM CONTAINS LIPID AND MICROPINOCYTOTIC VESICLES AT THE APEX $ILATED INTERCELLULAR SPACES OF TEN OCCUR BETWEEN ADJACENT CELLS AND MAY REPRESENT FUNCTIONALTRANSPORTCHANNELS-ICROVILLARCELLSABSORB NUTRIENTSPRODUCEDBYTHEUTERUSASWELLASEXOGENOUS MATERIALOFTHESIZEOFPROTEINS'RANULATEDCELLSUN DERGO CYCLES OF SYNTHESIS SO THAT DIFFERENT SECRETORY PHASESMAYBEOBSERVEDWITHINASINGLETISSUESECTION &IGURES$TO& #ELLSSEEMINGLYDEVOIDOFMOST ORGANELLES HAVE JUST UNDERGONE EXOCYTOSIS GRANULAR ENDOPLASMICRETICULUMISACTIVEINOTHERCELLSANDTHE SUPRANUCLEAR'OLGICOMPLEXISPROMINENT!SSYNTHE SISPROCEEDS THEAPICALCYTOPLASMBECOMESENGORGED WITH SECRETORY DROPLETS DISPLACING THE MITOCHONDRIA TOTHEBASEOFTHECELLFOLLOWINGEXOCYTOSIS THESYN

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&IGURE 4RANSMISSIONELECTRONMICROGRAPHOFASECTIONOFANINTERNALOVARIANEPITHELIALCELLOFTHEGOODEID8ENOTOCA EISENIAFTERINTRAOVARIANEXPOSURETOCATIONIZEDFERRITINFORSIXHOURS,ABELLINGOFTHEAPICALSURFACEOCCURSONLYATINTERVALS )NTRACELLULARLOCALIZATIONOFTHETRACERISMOSTDENSEINLARGE SOMEWHATMULTIVESICULATEDVACUOLESOFTHELYSOSOMALAPPARA TUS3OMETRACERISSEQUESTEREDINRELATIVELYELECTRON LUCENTVESICLESARROWHEADS #LUSTERSOFFERRITINMOLECULESAREPASSING THEBASALLAMINAARROWS 8 &ROM3CHINDLER REPRODUCEDWITHPERMISSION

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&IGURE 4RANSMISSION ELECTRON MICROGRAPHS OF POSSIBLE APOCRINE SECRETION IN INTERNAL OVARIAN EPITHELIAL CELLS OF TWO SPECIESOFGRAVIDGOODEIDS&ROM(OLLENBERGAND7OURMS ¶REPRODUCEDWITHPERMISSIONOF*OHN7ILEY3ONS )NC ! 4HEAPICALPORTIONOFANEPITHELIALCELLFROM'OODEAATRIPINNISCONTAINSLIPIDDROPLETSANDANUCLEUS.U !LARGEBLEB APPEARSTOBEABOUTTOPINCHOFFFROMTHERESTOFTHECELLARROWHEADS TOBERELEASEDINTOTHEOVARIANLUMENOL 8 " !LONG NARROWCYTOPLASMICEXTENSIONFROMANEPITHELIALCELLOF:OOGONETICUSQUITZEOENSISPROJECTSINTOTHEOVARIANLUMEN 4HECELLJUNCTIONSONTHELEFTANDRIGHTLATERALMEMBRANESAREUNUSUALLYCLOSETOONEANOTHERSUGGESTINGTHATTHEEXTENDED CYTOPLASMMAYSOONBESLOUGHED8

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&IGURE $RAWINGS FROM THE DISSECTED GRAVID OVARY OF THE JENYNSIID *ENYNSIA LINEATA WHERE EMBRYOS SUCKLE ON hNIPPLESv FORMED FROM THE LUMINAL WALL ,ONG RICHLY VASCULAR BRANCH ING FOLDS OF THE LUMINAL WALL FORM VILLI OVARIALES THAT GROW INTO ONE OPERCULAR CLEFT OF THE EMBRYO ESTABLISHING CONTACT BETWEEN MATERNALNUTRITIVETISSUEANDTHEEMBRYONICDIGESTIVETRACT&ROM 4URNER D ¶ REPRODUCED WITH PERMISSION OF *OHN 7ILEY 3ONS )NC ! !N EMBRYO IN LATE GESTATION ATTACHED TO A VILLUS OVARIALIS 4HE OVARIAN TISSUE EXTENDS THROUGH THE OPERCULAR OPENING INTOTHEPHARYNGEALCAVITYANDASMALLPORTIONPROTRUDESFROM THEMOUTH " !N EMBRYO IN LATE GESTATION TO ILLUSTRATE AN OPEN OPERCULAR CLEFT !BBREVIATIONS /0/ OPERCULAROPENING/64 OVARIANTISSUE

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&IGURE 4RANSMISSION ELECTRON MICROGRAPHS OF EPITHELIAL CELLS ON VILLI OVARIALES FROM THE JENYNSIID *ENYNSIA LINEATA &ROM3CHINDLERANDDE6RIES B¶REPRODUCEDWITHPERMISSIONOF*OHN7ILEY3ONS )NC ! %NDOCYTOTIC ACTIVITY IS INDICATED BY NUMEROUS ELEMENTS OF A VACUOLAR COMPLEX INCLUDING COATED VESICLES ARROWHEADS CUP SHAPEDVACUOLESARROWS ANDA'OLGICOMPLEX8 " 4HE GAP BETWEEN INTRAOVARIAN EPITHELIAL CELLS ALLOWS TRANSEPITHELIAL PASSAGE OF COARSE MATERIAL %NDOCYTOTIC ACTIVITY ARROWHEAD ISEVIDENTATTHESURFACEOFTHEOVARIANLUMEN/, 8 # -OSTADJACENTCELLSOFTHEINTRAOVARIANEPITHELIUMINTERDIGITATE8

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&IGURE 0HOTOMICROGRAPHSOFSEMITHINSECTIONSOFTROPHOTAENIAEOFTHEGOODEID8ENOOPHORUSCAPTIVUS&ROM3CHINDLER ANDDE6RIES BREPRODUCEDWITHPERMISSIONOFTHEAUTHORS ! +IDNEY SHAPEDCROSSSECTIONOFATROPHOTAENIA)TSCORECONSISTSOFLOOSEMESENCHYMALCONNECTIVETISSUECONTAININGTHIN WALLED BLOOD VESSELS ARROWS AND A CAPILLARY PLEXUS ARROWHEADS BENEATH THE EPITHELIUM4HE CIRCLE INDICATES A SMALL SEGMENTOFSTRATIlEDEPITHELIUM8 " 4ROPHOTAENIALEPITHELIUMSHOWINGCLOSELYAPPOSEDABSORPTIVECELLS) ANDTHOSEISOLATEDBYLARGEINTERCELLULARSPACES)) $ENSELYSTAINEDBASALCELLSARROWS UNDERLIEMOSTOFTHEABSORPTIVEEPITHELIUM8 # 3EGMENT OF BILAYERED SQUAMOUS EPITHELIUM BETWEEN ARROWHEADS )TS LEVEL IS SLIGHTLY RECESSED BELOW THE SURFACE OF THEBORDERINGABSORPTIVECELLS8

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&IGURE 4RANSMISSION ELECTRON MICROGRAPH OF SECTIONS THROUGH TROPHOTAENIAL EPITHELIAL CELLS FROM THE GOODEID !MECASPLENDENS&ROM,OMBARDIAND7OURMS B¶REPRODUCEDWITHPERMISSIONOF*OHN7ILEY3ONS )NC ! !NABSORPTIVECELLUNDERLAINBYASQUAMOUSBASALCELL&OURAREASOFCYTOPLASMICZONATIONCANBERECOGNIZEDINTHEAB SORPTIVECELL :ONE APICAL SURFACE ZONE :ONE APICAL CORTICAL ZONE ENDOCYTOTIC COMPLEX :ONE SUPRANUCLEAR ZONECONTAININGLARGEMEMBRANOUSINCLUSIONSANDMITOCHONDRIAAND:ONE THENUCLEAR SUBNUCLEARZONE!GRANULARAND GRANULAR ENDOPLASMIC RETICULUM OCCUPIES THE PARANUCLEAR REGION4HE 'OLGI COMPLEX LIES IN A LATERAL OR BASAL POSITION 4HESQUAMOUSBASALCELLSPOSSESSELECTRON LUCENTCYTOPLASMARROW 4HEEPITHELIALCELLSARESEPARATEDFROMACAPILLARYCA BYADELICATEBASALLAMINA8 " !PICALREGIONOFANABSORPTIVECELL-ICROVILLIMV EXTENDFROMHECONVOLUTEDCELLSURFACE4HEOUTERLEAmETOFTHEPLASMA LEMMAISCOATEDWITHAlNElBRILLARMATERIAL4HEAPICALCANALICULARSYSTEMAC CONTAINSTUBULARPROlLESARROW ASSOCIATED WITHCOLLECTINGVESICLES-ITOCHONDRIAMI OFTHESUPRANUCLEARZONEARENUMEROUSANDSITUATEDADJACENTTOTHENUCLEUSNU AV APICALVESICLE8 # 4HE LATERAL CYTOPLASM OF ADJACENT ABSORPTIVE CELLS CONTAINS THE TUBULAR CISTERNAL COMPLEX ARROWS AND ELEMENTS OF THEGRANULARENDOPLASMICRETICULUMGER LP LATERALPLASMALEMMANU NUCLEUS8 $ 4HESUBNUCLEARREGIONOFANABSORPTIVECELLCONTAINSNUMEROUSDENSEINCLUSIONSANDAWELLDEVELOPED'OLGICOMPLEXGO )NVAGINATIONSOFTHELATERALCELLSURFACESFORMELEMENTSOFTHETUBULARCISTERNALCOMPLEXARROW 4HECELLSRESTONABASAL LAMINABL DI DENSEINCLUSION8

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&IGURE 4RANSMISSION ELECTRON MICROGRAPHS OF SECTIONS THROUGH THE APICAL REGIONS OF TROPHOTAENIAL ABSORPTIVE CELLS OFTHEGOODEID!MECASPLENDENSlXEDAFTERAPERIODOFCONTINUOUSEXPOSURETOHORSERADISHPEROXIDASE&ROM,OMBARDIAND 7OURMS C¶REPRODUCEDWITHPERMISSIONOF*OHN7ILEY3ONS )NC ! !FTERMINUTESEXPOSURE REACTIONPRODUCTISPRESENTWITHINAFEWAPICALVESICLESANDELEMENTSOFTHEAPICALCANALICULAR SYSTEMARROWS 8 " !FTERMINUTESEXPOSURE UPTAKEOCCURSBYWAYOFENDOCYTOSISOFTHEAPICALPLASMAMEMBRANEARROWS 2EACTIONPROD UCTISPRESENTWITHINAPICALCANALICULIANDCOLLECTINGVESICLES,ARGESUPRANUCLEARLYSOSOMESSITUATEDABOVETHENUCLEUS SHOWNOPEROXIDASEACTIVITY8 # !FTERMINUTESEXPOSURE THEREACTIONPRODUCTISPRESENTWITHINAPICALCANALICULI COLLECTINGVESICLES ANDLARGESUPRA NUCLEARVESICLES8

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&IGURE #ONTINUED $ !FTERMINUTES THEREACTIONPRODUCTISPRESENTWITHINTHEAPICALCANALICULARSYSTEM COLLECTINGVESICLES ANDENLARGED SUPRANUCLEARLYSOSOMES8 % !N ENTIRE ABSORPTIVE CELL IS SHOWN AFTER ONE HOURS EXPOSURE 4HE REACTION PRODUCT IS PRESENT WITHIN APICAL CANALICULI COLLECTING VESICLES AND GREATLY ENLARGED SUPRANUCLEAR LYSOSOMES #OLLECTING VESICLES FUSE WITH SUPRANUCLEAR VESICLES ARROW 2ESIDUALBODIESCONTAININGmOCCULENTMATERIALAREPRESENT0EROXIDASEACTIVITYISALMOSTEXCLUSIVELYLOCALIZEDIN THESUPRANUCLEARREGIONOFTHECELL%XOGENOUSPEROXIDASEACTIVITYISNOTDETECTEDWITHINTHETROPHOTAENIALCONNECTIVETISSUE ORVASCULARELEMENTS8 !BBREVIATIONS AC APICALCANALICULIBL BASALLAMINACA CAPILLARYCV COLLECTINGVESICLESIS INTERCELLULARSPACEMV MICRO VILLINU NUCLEUSRB RESIDUALBODYSV SUPRANUCLEARVESICLES

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&IGURE $IAGRAMMATIC SUMMARY OF THE PROPOSED PATHWAY BY WHICH PROTEINS ARE TRANSFERRED ACROSS THE TRO PHOTAENIAL PLACENTA IN THE GOODEID !MECA SPLENDENS ! THESYNTHESISANDRELEASEOFPROTEIN CONTAININGSECRETIONS BYCELLSOFTHEINTERNALOVARIANEPITHELIUM" UPTAKEOFOVAR IANSECRETIONSBYTHETROPHOTAENIALEPITHELIUMBYENDOCYTO SIS# TRANSFERANDPASSAGEOFPROTEINCOMPONENTSTHROUGH THEAPICALCANALICULARSYSTEMANDITSPROGRESSIVEACCUMULA TION IN COLLECTING VESICLES $ FUSION OF COLLECTING VESICLES WITHSTANDINGSUPRANUCLEARSECONDARYLYSOSOMES% GROWTH OF STANDING LYSOSOMES BY ACCRETION OF COLLECTING VESICLES ANDOROTHERLYSOSOMES& ENZYMATICHYDROLYSISOFPROTEINS WITHINSTANDINGLYSOSOMES' DISCHARGEOFTHEPRODUCTSOF PROTEIN HYDROLYSIS AMINO ACIDS AND PEPTIDES VIA LATERAL AND BASAL CELL SURFACES ( PASSAGE OF COMPONENTS OF LOW MOLECULAR WEIGHT ACROSS THE BASAL MATRIX AND CONNEC TIVE TISSUE CORE AND THEIR ENTRY INTO THE EMBRYONIC VASCU LAR SYSTEM BY TRANSPORT ACROSS THE CAPILLARY ENDOTHELIUM &ROM ,OMBARDI AND 7OURMS C ¶ REPRODUCED WITH PERMISSIONOF*OHN7ILEY3ONS )NC

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&IGURE 4RANSMISSION ELECTRON MICROGRAPH OF A SECTION THROUGH THE STRATIlED TROPHOTAENIAL EPITHELIUM OF THE GOODEID 8ENOOPHORUS CAPTIVUS 4HE OVARIAN LU MEN /, IS SHOWN AT THE TOP (UGE INTERCELLULAR SPACES )#3 HAVEAPPEAREDBETWEENTHESTRATIlEDPAVEMENTCELLS !DJOINING CELLS ARE CONNECTED BY CYTOPLASMIC PROCESSES 4HEARROWINDICATESINTERDIGITATIONSBETWEENADJACENTCELLS 4HE EPITHELIUM IS SEPARATED FROM LOOSE SUBEPITHELIAL CON NECTIVE TISSUE BY A DELICATE BASAL LAMINA ", 8 &ROM 3CHINDLER AND DE 6RIES B REPRODUCED WITH PERMISSIONOFTHEAUTHORS

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&IGURE )NTERCELLULARSPACESINTHETROPHOTAENIALEPITHELIUMMAYHAVEANEXCRETORYROLEINSTORINGWASTESORPLAYAPAS SIVEROLEINTHEACQUISITIONOFIMMUNITY4HESEARETRANSMISSIONELECTRONMICROGRAPHOFSECTIONSTHROUGHOFNEAR TERMEMBRYOS OFTHEGOODEID'IRARDINICHTHYSVIVIPARUS&ROM3CHINDLERANDDE6RIES A¶REPRODUCEDWITHPERMISSIONOF*OHN7ILEY 3ONS )NC ! 4HELATERALPLASMALEMMASOFABSORPTIVECELLSARELINEDWITHLAMELLARSTRUCTURESANDMEMBRANOUSBLEBSAREEXTRUDEDINTO THEINTERCELLULARSPACE2%2 GRANULARENDOPLASMICRETICULUM8 " !SINGLELAYEROFmATTENEDCELLS RESTINGONTHEBASALLAMINA"- UNDERLIESTHEABSORPTIVEEPITHELIUM4HESEBASALCELLS ARECONNECTEDBYHIGHLYCONVOLUTEDINTERDIGITATIONSARROW !LEUCOCYTE, CANBESEENINTHEINTERCELLULARSPACES)#3 BETWEENTHETWOTYPESOFEPITHELIALCELLSANOTHERISPRESENTINTHETROPHOTAENIALSTROMA8 # ,EUCOCYTES LARGELYHETEROPHILICGRANULOCYTES OCCUPYTHECONNECTIVETISSUECOREOFATROPHOTAENIA8

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&IGURE 4RANSMISSION ELECTRON MICROGRAPHS OF SECTIONS OF THE SUR FACE EPITHELIUM OF AN EMBRYO OF THE MATROTROPHIC POECILIID (ETERANDRIA FORMOSA&ROM'ROVEAND7OURMS ¶REPRODUCEDWITHPERMISSIONOF *OHN7ILEY3ONS )NC ! "ASAL CELL OF THE SURFACE EPITHELIUM OF A MID STAGE EMBRYO SHOWING A CILIUM AND ITS BASAL BODY 4HE DENSE EXTRACELLULAR GRANULES ARROW HEADS MAYREPRESENTYOLK8 " !BASALCELLFROMTHESURFACEEPITHELIUMOFAMID STAGEEMBRYOSHOWING ACOATEDPITARROWHEAD ATITSAPICALSURFACE8 # 3URFACEEPITHELIUMOFALATESTAGEEMBRYOFROMAREGIONSIMILARTOTHAT SHOWNIN&IGURE! 4HEEPITHELIUMCONSISTSOFSUPERlCIALANDBAS ALCELLS4HESUPERlCIALCELLSLACKMICROVILLIANDARETHINNERTHANABSORP TIVESUPERlCIALCELLSWITHMICROVILLI )NSET CYTOPLASMIC lLAMENTS ARROWHEAD IN THE APICAL CYTOPLASM OF A SUPERlCIALCELL8 $ 3URFACEEPITHELIUMOFALATESTAGEEMBRYOFROMAREGIONSIMILARTOTHAT SHOWNIN&IGURE!ILLUSTRATINGTHEJUNCTIONBETWEENANABSORPTIVE CELLBEARINGMICROVILLIANDANON MICROVILLOUSCELL!LTHOUGHTHEMOR PHOLOGYOFTHETWOTYPESOFSUPERlCIALCELLSDIFFERSSTRIKINGLY THEREIS NOAPPARENTDIFFERENCEINTHEMORPHOLOGYOFTHEBASALCELLS4HEBASAL LAMINAISINDICATEDBYARROWHEADS8

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CHORION TELEOST CHORION VARIATIONS CHORION VIVIPAROUSlSH CHORIONS ANALYSISOFHOMOGENATES CHROMATININATRESIA CHROMATIN NUCLEOLUSPHASE CHROMOSOMES TETRAD CIRCUMNUCLEARRING CLEAVAGE FOLLICULAR TELEOST CLEFTOFPENETRATION CLOACA CYCLOSTOME CLUBZONE OVIDUCTALGLAND ELASMOBRANCH COATEDPITSINOOLEMMA COATEDVESICLESINOOLEMMA COELOMICmUID COELOMICSACINLUMINALGESTATION COELOMICSAC ABSORPTIONINVIVIPARITY COLLAGENINPOSTOVULATORYFOLLICLES COLLOIDOSMOTICPRESSURE COMPARTMENTSINLUMINALGESTATION CONTRACTIONS THECA COPULATION COPULATION ELASMOBRANCH CORPORAATRETICA CORPORAATRETICA ELASMOBRANCH CORPORALUTEA DEGENERATION CORPORALUTEA ELASMOBRANCH CORPUSLUTEUM CORPUSLUTEUMOFATRESIA CORPUSLUTEUM DISAPPEARANCE CORPUSLUTEUM FORMATION CORTEX GONADAL CORTEX OVARY CORTICALALVEOLINEARLYVITELLOGENESIS CORTICALALVEOLI CORTICALALVEOLIINATRESIA CORTICALALVEOLIOFANIMALPOLE CORTICALALVEOLIOFVEGETALPOLE CORTICALALVEOLI COMPOSITION CORTICALALVEOLI EXPULSION CORTICALALVEOLI EXTRUSION CORTICALALVEOLI GRADIENT CORTICALALVEOLI LIMITINGMEMBRANE CORTICALALVEOLI REMNANTS CORTICALALVEOLI STRUCTURE CORTICALALVEOLUSSTAGE CORTICALENDOPLASMICRETICULUM CORTICALOOPLASM CORTICALREACTION CORTICALREACTION TRIGGER

CORTICALVESICLES EXOCYTOSIS CRYSTALSINYOLKGRANULES CYSTOVARIANOVARY TELEOST CYTOCHALASIN" CYTOPLASMICBRIDGES CYTOPLASMICCONTINUITY CYTOSKELETON CYTOSKELETONINOVULATION $ DAYLENGTHANDOVULATION DElNITIVEFOLLICLE DEGENERATINGFOLLICLES ELASMOBRANCH DELLEINTELEOSTFOLLICLE DENSE COREDGRANULES DEPOLARIZATIONOFOOLEMMA DESMOSOMES DESMOSOMES PERITONEALCELLS DESMOSOMES RUDIMENTARY DEVELOPINGFOLLICLES ELASMOBRANCH DEVELOPINGFOLLICLES SEQUENTIALARRAY DEVELOPMENT FOLLICULAR TELEOST DIFFERENTIATION GONADAL DIPLOTENEOOCYTES $.!REPLICATION DUCT OVIDUCTALGLAND ELASMOBRANCH DUCTUSVITELLO INTESTINALIS % EGGACTIVATION EGGCAPSULEINSHARKPLACENTA EGGCAPSULEINVIVIPARITY ELASMOBRANCH EGGCAPSULEWALL ELASMOBRANCH COMPOSITION EGGCAPSULE ABSENCEINBLUESHARK EGGCAPSULE ELASMOBRANCH EGGCAPSULE ELASMOBRANCH LAYERS EGGCAPSULE TANNING ELASMOBRANCH EGGCAPSULE VIVIPAROUSSHARK EGGCASE EGGENVELOPEINFOLLICULARGESTATION EGGMEMBRANEINFOLLICULARGESTATION EGG TRANSPORT ELECTRON LUCENTLAYER: EMBRYOTROPH EMBRYOTROPHINLUMINALGESTATION EMBRYOTROPH OSMOLARITY EMBRYOTROPH TELEOST EMBRYOTROPH UPTAKE ENDOCYTOSIS ENDOCYTOSISINLUMINALGESTATION

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ENDOCYTOSISINTROPHOTAENIALCELLS ENDOCYTOSISOFVITELLOGENIN ENDOCYTOTICVESICLES ENDODERMALEPITHELIUM SHARK ENDOPLASMICRETICULUM AGRANULAR ENDOTHELIALCELLSOFFOLLICULARCAPILLARIES ENDOTHELIALCELLSOFLYMPHSPACES ENDOTHELIALCELLS CICHLIDFOLLICLE ENDOVARIANCAVITY ENLARGEMENTOFOOCYTES ENTEROENDOCRINECELLS ENVELOPEINVIVIPAROUSPOECILIIDS ENVELOPEPROTEINSINPLASMA ENVELOPE LAMPREY ENVELOPE STURGEON ENVELOPESECONDARY ENVELOPES ENVELOPES FOLLICULAR EPIGONALORGANS ELASMOBRANCH EPITHELIUM OVARIANLUMINAL EXOCYTOSIS EXOCYTOSISOFCORTICALVESICLES EXOCYTOSIS CORTICALREACTION EXOCYTOSIS DEPOSITIONOFSECONDARYENVELOPE EXOCYTOSIS DEPOSITIONOFZONAPELLUCIDA EXOGENOUSNUTRIENTS UPTAKE EXOGENOUSLYDERIVEDYOLKPROTEINPRECURSORS EXPULSIONOFEGG EXTERNALGILLlLAMENTSINSHARKEMBRYOS EXTRAEMBRYONICCOELOM EXTRAVASCULARSPACES FOLLICLE & FEMALE SPECIlCSERUMPROTEIN FERTILIZATION FERTILIZATIONCONE FERTILIZATION EARLYSTAGES FERTILIZATION INTERNAL FERTILIZATION INTERNAL ELASMOBRANCH FERTILIZATION INTERNAL TELEOST FERTILIZATION INTRAFOLLICULAR FERTILIZATION LAMPREY FERTILIZATION TELEOST lBROUSTUFT LAMPREY lLAMENTS MEDAKAEGG lRSTPOLARBODY mUIDOFOVULATION LAMPREY mUIDYOLK FOETALYOLKSAC BLUESHARK FOLLICLE FORMATION

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FOLLICLE OVARIAN FOLLICULARCELLMICROVILLI WITHDRAWAL FOLLICULARCELLS FOLLICULARCELLSANDMICROPYLARCANAL FOLLICULARCELLSINATRESIA FOLLICULARCELLSINAXISFORMATION FOLLICULARCELLSINENVELOPEFORMATION FOLLICULARCELLSINGESTATION FOLLICULARCELLSINMACROMOLECULARUPTAKE FOLLICULARCELLSINMATROTROPHICTELEOST FOLLICULARCELLSINOVULATION FOLLICULARCELLSINOVULATION LAMPREY FOLLICULARCELLSINPOSTOVULATORYFOLLICLES FOLLICULARCELLSINPOSTOVULATORYFOLLICLES HAGlSH FOLLICULARCELLSINYOLKUPTAKE LAMPREY FOLLICULARCELLS CONTRACTIONS FOLLICULARCELLS ELASMOBRANCH FOLLICULARCELLS ENVELOPEFORMATION FOLLICULARCELLS FUNCTIONS FOLLICULARCELLS 'OLGICOMPLEX FOLLICULARCELLS HORMONES FOLLICULARCELLS HYPERTROPHY FOLLICULARCELLS INTERCELLULARSPACES FOLLICULARCELLS INVASIVE FOLLICULARCELLS LAMPREY FOLLICULARCELLS LYSOSOMES FOLLICULARCELLS MECHANICALFUNCTION FOLLICULARCELLS MICROPYLE HAGlSH FOLLICULARCELLS ORGANELLES FOLLICULARCELLS ORIGIN FOLLICULARCELLS PASSAGEOFMATERIALS FOLLICULARCELLS PHAGOCYTOSISINATRESIA FOLLICULARCELLS POLARITY FOLLICULARCELLS REGRESSION FOLLICULARCELLS SEABASS FOLLICULARCELLS SECONDARYENVELOPE FOLLICULARCELLS STEROIDOGENESIS FOLLICULARDEVELOPMENT TELEOST FOLLICULARENVELOPES FOLLICULAREPITHELIUM FOLLICULAREPITHELIUMINCHORIONFORMATION FOLLICULAREPITHELIUMINFOLLICULARGESTATION FOLLICULAREPITHELIUMINMATROTROPHICNUTRITION FOLLICULAREPITHELIUMINNUTRIENTTRANSFER FOLLICULAREPITHELIUMINOVULATION FOLLICULAR EPITHELIUM IN POSTOVULATORY FOLLICLES FOLLICULAREPITHELIUM BARRIER FOLLICULAREPITHELIUM BASEMENTMEMBRANE FOLLICULAREPITHELIUM CICHLID

FOLLICULAREPITHELIUM DOGlSH FOLLICULAREPITHELIUM ELASMOBRANCH FOLLICULAREPITHELIUM GUPPYPLACENTA FOLLICULAREPITHELIUM HAGlSH FOLLICULAREPITHELIUM HYPERTROPHY FOLLICULAREPITHELIUM LAMPREY FOLLICULAREPITHELIUM LIPIDCELLS FOLLICULAREPITHELIUM ORIGIN FOLLICULAREPITHELIUM PASSAGEOFMATERIALS FOLLICULAREPITHELIUM PREOVULATORYCHANGES LAMPREY FOLLICULAREPITHELIUM RAY INTERCELLULARJUNCTIONS FOLLICULAREPITHELIUM SEABASS INTERCELLULARJUNCTIONS FOLLICULAREPITHELIUM STRATIlED RAY FOLLICULAREPITHELIUM TELEOST FOLLICULARGESTATION FOLLICULARLAMINA SYNGNATHIDOVARY FOLLICULARLIGAMENT HAGlSH FOLLICULARPLACENTA FOLLICULARPLACENTA POECILIID FOLLICULARRUPTURE LAMPREY FOLLICULARSTEROIDOGENESIS FOLLICULARSTEROIDOGENESIS ELASMOBRANCH FOLLICULARTHECA FOLLICULOGENESIS FOLLICULOGENESIS ELASMOBRANCH FUSIONOFYOLKDROPLETS ' GAPJUNCTIONS GAPJUNCTIONSINFOLLICULARCAPILLARIES GAPJUNCTIONS MESOTHELIALCELLS GELATINOUSMASS 3CORPAENIFORMES GENITALPORE CYCLOSTOME GENITALPORE TELEOST GENITALRIDGE GENITALSYSTEMS ORIGIN GENTIALPORE !GNATHA GERMCELLNESTS LAMPREY GERMINALDENSEBODIES GERMINALEPITHELIUM GERMINALRIDGE GERMINALRIDGE HAGlSH GERMINALRIDGE SYNGNATHIDOVARY GERMINALVESICLE GERMINALVESICLEBREAKDOWN GERMINALVESICLEINVITELLOGENESIS GERMINALVESICLE BREAKDOWN GERMINALVESICLE MIGRATION

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GESTATIONINMATROTROPHICTELEOST GESTATION !NABLEPS GESTATION ELASMOBRANCH GESTATION FOLLICULAR GESTATION LUMINAL GESTATION SHARK GESTATION TELEOST GILLS ABSORPTIONINVIVIPARITY GONADALANLAGE GONADALDIFFERENTIATION GONADALEPITHELIUM GONADALEPITHELIUM ELASMOBRANCH GONADALPRIMORDIA GONADALRIDGE GONADOSOMATICINDEX GONADOTROPIN GONADOTROPINRECEPTORS GONODUCT TELEOST GONOPODIUM GRADIENTOFCORTICALALVEOLI GRANULOSACELLS GROUP SYNCHRONOUSOVARIES GROWTHOFOOCYTES '6"$ GYMNOVARIANOVARY TELEOST

HYDROLYSISOFYOLKPROTEINS HYOSOPHORIN HYOSOPHORINASE HYPERTROPHY OF FOLLICULAR CELLS IN POSTOVULATORY FOL LICLES

( HAEMATROPHICEXCHANGE PLACENTAL HAEMATROPHICNUTRITION PLACENTALSHARKS HAEMATROPHICPLACENTA ELASMOBRANCH HAEMATROPHICTRANSFER SHARKPLACENTA HAEMOPOIETICTISSUE ELASMOBRANCH HARDENING CHORION HATCHING HATCHINGENZYME HEADlLAMENT LAMPREYSPERM HEPATOSOMATICINDEX HERMAPHRODITISM HETEROSYNTHETICORIGINOFYOLKPROTEINS ( HYOSOPHORIN HISTOTROPH HONEYCOMBCELL HAGlSH HORMONEPRODUCTIONINPOSTOVULATORYFOLLICLES HORMONESYNTHESISTWO CELLMODEL HORMONE PITUITARY HORMONES HORMONESOFOVARIANFOLLICLES HUMANCHORIONICGONADOTROPIN HYDRATIONOFOOCYTE HYDROCORTISONE

* JELLYCOAT JUNCTIONALCOMPLEXES JUNCTIONALTYPESINFOLLICULAREPITHELIUM JUXTANUCLEARCOMPLEX JUXTANUCLEARCOMPLEX FUNCTION

) IMMUNOLOGICALBARRIER FOLLICULARGESTATION IMMUNOLOGICALBARRIER OVIDUCT TELEOST IMPLANTATION SHARK INDUCEDOVULATION INSEMINATION INTERCELLULARBRIDGES INTERCELLULARBRIDGES FOLLICULAREPITHELIUM RAY INTERCELLULARPASSAGE FOLLICULAREPITHELIUM INTERCELLULARSPACES TROPHOTAENIALEPITHELIUM INTERNALGAMETICASSOCIATION INTERSEXUALITY INTERSTITIALCELLSOFTHEOVARY INTERSTITIALGLANDCELLS INTERSTITIALTISSUE INTROMITTENTORGAN IONTRANSPORT IONICREGULATION ISTHMUS OVIDUCT ELASMOBRANCH

, LAMELLAEOFEGGCAPSULE DOGlSH LAMELLAE ZONAPELLUCIDA LAMPBRUSHCHROMOSOMES LECITHOTROPHY LECITHOTROPHY COELACANTH LECITHOTROPHY VIVIPAROUSELASMOBRANCH LECTINS LECTINSINCORTICALREACTION LEPTOTENEOOCYTES LEUCOCYTESINATRESIA , HYOSOPHORIN LIPID LIKECELLSINFOLLICULAREPITHELIUM LIPIDDROPLETSINVITELLOGENESIS LIPIDDROPLETS FORMATION LIPIDINCORTICALALVEOLUSSTAGE LIPIDINEARLYVITELLOGENESIS

LIPIDMASS LIPIDYOLKDROPLETS LIPOFUSCIN LIPOVITELLIN LUMINALEPITHELIUM OVARY LUMINALEPITHELIUM OVARY SECRETION LUMINALGESTATION TELEOST LUTEALBODIES LYMPHATICCOMPARTMENT OVARY LYMPHATICSPACES LYSOSOMALCOMPARTMENT LYSOSOME LIKEBODIES LYSOSOMES LYSOSOMESINFOLLICULARCELLS LYTICENZYMESINOVULATION MACROPHAGES MARGINALCLEFTSINOVARIANLUMINALEPITHELIUM MATROTROPHY MATROTROPHY EXTREME MATURATION MATURATIONDIVISION MATURATIONINDUCINGSTEROID MATURATION INDUCINGHORMONE MATUREEDGE SYNGNATHIDOVARY MEDULLA GONADAL MEIOSIS MEIOSIS RESUMPTION MEIOTICPROPHASE) MEIOTICSPINDLE FORMATION MEMBRANERESERVOIR UTERUS ELASMOBRANCH MESODERM YOLKSAC SHARK MESONEPHRICDUCT ELASMOBRANCH MESOTHELIUM MESOVARIUM METAPHASE) METAPHASE)) MICROAPOCRINESECRETION MICROlLAMENTBUNDLESINVITELLOGENESIS MICROlLAMENTS MICROlLAMENTS CONTRACTILITYINTHECALCELLS MICROPINOCYTICPITSINPERITONEALCELLS MICROPINOCYTOSISINFOLLICULARCAPILLARIES MICROPINOCYTOSIS OOLEMMA MICROPLICAEOFOOLEMMA MICROPYLARAPPARATUS HAGlSHEGG MICROPYLARCANAL MICROPYLARCANAL NARROWING MICROPYLARCELL

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MICROPYLARCELLINAXISDETERMINATION MICROPYLARCELL DEGENERATION MICROPYLARCELL STRUCTURE MICROPYLARCELL ULTRASTRUCTURE MICROPYLARFUNNEL HAGlSH MICROPYLARPLUG MICROPYLARPROCESS MICROPYLE MICROPYLECLOSURE MICROPYLERESISTSPOLYSPERMY MICROPYLE ABSENCEINVIVIPAROUSELASMOBRANCH MICROPYLE ABSENCE LAMPREYEGG MICROPYLE BLENNYEGG MICROPYLE FORMATION MICROPYLE HAGlSH MICROPYLE POSITIONING MICROPYLE SURFACEPATTERNS MICROPYLES CLADISTICANALYSES MICROPYLES CLASSIlCATION MICROPYLES MULTIPLE IN!CIPENSERIFORMES MICRORIDGESINTRANSPORT MICROTUBULARCYTOSKELETON MICROTUBULEMIMICS MICROTUBULE LIKEELEMENTS MICROTUBULES MICROTUBULESINCHORIONIClLAMENTS MICROVESICLESINFOLLICULARCAPILLARIES MICROVILLIINPORECANALS MICROVILLI OF FOLLICULAR CELLS MICROVILLIOFOOCYTE MICROVILLIOFSPERMBINDINGSITE MICROVILLIOFSPERMENTRYSITE MICROVILLI DETACHMENTINOVULATION MICROVILLI GAPJUNCTIONS MICROVILLI WITHDRAWALFROMPORECANALS MICROVILLOUSCELLS MIGRATIONOFGERMINALVESICLE MIGRATIONOFPRIMORDIALGERMCELLS -)( -)3 MITOCHONDRIAWITHTUBULARCRISTAE MITOCHONDRIAL ASSOCIATEDGRANULARMATERIAL MITOTICREST MODELOFHORMONALSYNTHESIS MONONUCLEAR PHAGOCYTES IN POSTOVULATORY FOLLICLES MUCOPOLYSACCHARIDES LAMPREYFOLLICULARCELLS MUCOSOMES

-àLLERIANDUCT -àLLERIANDUCT ELASMOBRANCH MULTIPLEMICROPYLESIN!CIPENSERIFORMES MULTIVESICULARBODIES . NASCENTCORTICALALVEOLI NERVEBUNDLES OVARIAN NESTSOFEARLYGERMCELLS NIDAMENTALGLAND OVIDUCT ELASMOBRANCH NIPPLES SUCKLINGINLUMINALGESTATON NITROGENOUSWASTEINEMBRYOS NONATTACHINGlLAMENTS MEDAKAEGG NUAGE NUCLEARMEMBRANEINATRESIA NUCLEARPORES NUCLEARCYTOPLASMICRATIO NUCLEOLI NUCLEOLI MULTIPLE NURSECELLS ELASMOBRANCH NURSECELLS LAMPREY NUTRIENTTRANSFER NUTRIENTTRANSFERINMATROTROPHICTELEOST NUTRITIVEEPITHELIUMINLUMINALGESTATION / OCCLUDINGJUNCTIONS OESTRADIOL OESTRADIOL ` OESTRADIOL ÌNELASMOBRANCHS OESTRADIOL ` SYNTHESIS OESTROGEN OOCYTEENLARGEMENT OOCYTEENVELOPES OOCYTE)) OOCYTEMICROVILLI WITHDRAWAL OOCYTENUCLEUSINATRESIA OOCYTEVOLUME OOCYTE EXPULSION OOCYTE GROWTH OOCYTE HAGlSH OOCYTE HYDRATION OOCYTE UPTAKEOFMATERIALS OOGENESIS OOGONIA OOGONIAENTERINGMEIOTICPROPHASE OOGONIA HAGlSH OOGONIA MEIOSIS OOGONIA PIPElSH OOLEMMA

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OOLEMMAINATRESIA OOLEMMA DEPOLARIZATION OOLEMMA EXOCYTOSIS OOLEMMA INDENTATION OOLEMMA MOSAIC OOLEMMA UPTAKEBYMICROPINOCYTOSIS OOPHAGY OOPHAGY COELACANTH OOPHAGY VIVIPAROUSELASMOBRANCH OOPLASMINATRESIA OPERCULARRING HAGlSH ORIENTATIONOFSPERMATOZOA ORIGINOFTHEGENITALSYSTEMS ORNAMENTATION SECONDARYENVELOPE OSMOLARITYOFEMBRYOTROPH OSMOLARITYOFPERIVITELLINEmUID OSMOREGULATIONINABSORPTIVEEPITHELIA OSMOREGULATIONINAPLACENTALYOLKSACVIVIPARITY OSMOREGULATIONINMATROTROPHICGESTATION OSMOREGULATIONINPERIVITELLINESPACE OSMOREGULATION SHARKUTERUS OSMOREGULATION UTERUS BLUESHARK OSMOTICENVIRONMENT UTERUS ELASMOBRANCH OSMOTICPOTENTIAL OSMOTICUPTAKEOFWATER OSMOTICUPTAKEOFWATER LAMPREYFOLLICLE OSTIUMTUBAEINVIVIPARITY ELASMOBRANCH OSTIUM ELASMOBRANCH OSTIUM ELASMOBRANCHOVIDUCT OVARIANARTERY OVARIANCAVITY OVARIANEPITHELIUMINLUMINALGESTATION OVARIANmUID OVARIANFOLLICLES OVARIANFOLLICLES DIAMETER OVARIANFOLLICLES HORMONES OVARIANHORMONES OVARIANLUMEN OVARIANLUMINALEPITHELIUM OVARIANLUMINALWALL TELEOST OVARIANMATURITY OVARIANSTROMA OVARY OVARYINFOLLICULARGESTATION OVARY CYSTOVARIAN OVARY ELASMOBRANCH OVARY GYMNOVARIAN OVARY HAGlSH OVARY LAMPREY OVARY SYNGNATHID

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OVARY TELEOST OVERRIPEEGGS OVIDUCT OVIDUCTINOVIPARITY OVIDUCTINVIVIPARITY ELASMOBRANCH OVIDUCT ELASMOBRANCH OVIDUCT ELASMOBRANCH BASICPLAN OVIDUCT EPITHELIUM OVIDUCT 3CORPAENIFORMES OVIDUCT TELEOST OVIDUCTALGLANDINVIVIPARITY ELASMOBRANCH OVIDUCTALGLAND ELASMOBRANCH OVIDUCTAL GLAND ELASMOBRANCH CAPSULE PRODUCTION OVIDUCTALGLAND ELASMOBRANCH INNERVATION OVIDUCTALGLAND ELASMOBRANCH SPERMSTORAGE OVIDUCTALGLANDS ZONATION ELASMOBRANCH OVIGEROUSEPITHELIUM 3CORPAENIFORMES OVIGEROUSFOLDS OVIGEROUSFOLDSINLUMINALGESTATION OVIGEROUSFOLDS TELEOST OVIGEROUSSTROMA 3CORPAENIFORMES OVISAC OVISAC TELEOST OVULATION OVULATIONINOVIPAROUSTELEOSTS OVULATION LAMPREY OVULATION LYTICENZYMES OVULATION INDUCINGENZYMES OVUM OVUM DISINTEGRATIONINATRESIA 0 PACHYTENESTAGEOFPROPHASE) PALLIALSUBSTANCE PAPILLARYZONE OVIDUCTALGLAND ELASMOBRANCH PARACRINEFUNCTION PARACRINESYSTEM PARAPLACENTALSITES SHARKUTERUS PAROVARIANCAVITY PARTURITION TELEOST PATHWAY BLOOD EMBRYOTROPH LUMINALGESTATION PAVEMENTCELLS TROPHOTAENIAL PAVEMENTEPITHELIUM TROPHOTAENIAL PEDUNCLE FOLLICLEBEARING PENETRATIONBYSPERMATOZOA PENETRATIONOFOOLEMMA PERICARDIALSACINLUMINALGESTATION PERICARDIALSAC ABSORPTIONINVIVIPARITY

PERICYTES PERIFOLLICULARCAPILLARIES PERINUCLEARDENSEBODIES PERINUCLEARNUAGES PERINUCLEARRING PERINUCLEARRINGOFMITOCHONDRIA PERINUCLEOLUSPHASE PERITONEALCELLS PERITONEALFOLDS PERIVITELLINEmUID OSMOLARITY PERIVITELLINESPACE PERIVITELLINESPACE CREATION PERIVITELLINESPACE LAMPREY PERIVITELLINESPACE SPHERICALBODIES PERIVITELLINESPACE WATERUPTAKE PHAGOCYTESINPOSTOVULATORYFOLLICLES PHAGOCYTESINPOSTOVULATORYFOLLICLES HAGlSH PHAGOCYTOSISINATRESIA PHEROMONES PHOSPHOINOSITIDECASCADE PHOSVITIN PINOCYTOSISINSMOOTHMUSCLE PINOCYTOSIS FOLLICULARCAPILLARIES PINOCYTOTICVESICLES PITUITARYCONTROL PITUITARYGONADOTROPIN PLACENTA PLACENTA !NABLEPS PLACENTA BRANCHIAL PLACENTA BUCCAL PLACENTA ELASMOBRANCH PLACENTA FOLLICULAR PLACENTA GUPPY PLACENTA HAEMATROPHIC ELASMOBRANCH PLACENTA MATROTROPHIC PLACENTA NON DECIDUATE SELACHIAN PLACENTA NON INVASIVE SELACHIAN PLACENTA POECILIID PLACENTA SHARK PLACENTA TROPHOTAENIAL PLACENTA YOLKSAC PLACENTALBARRIER GUPPY PLACENTALBARRIER SHARK PLACENTALEFlCIENCY PLACENTALVIVIPARITY ELASMOBRANCH PLACENTOTROPHY PLASMAGONADOTROPIN)) POLARBODY POLARITY POLYRIBOSOMESANDANNULATELAMELLAE

POLYSIALOGLYCOPROTEINS POLYSPERMY POLYSPERMYPREVENTION HAGlSH POLYSPERMY BLOCK POLYSPERMY PREVENTION PORECANALS PORECANALSINCHORION PORECANALS DISAPPEARANCE PORECANALS ELASMOBRANCH PORECANALS EXCHANGEOFMETABOLITES PORECANALS FORMATION PORECANALS LAMPREY PORECANALS MICROVILLI PORECANALS WITHDRAWALOFMICROVILLI POST '6"$ POSTOVULATORYCORPUSLUTEUM POSTOVULATORYCORPUSLUTEUM FORMATION POSTOVULATORYFOLLICLES POSTOVULATORYFOLLICLES DEGENERATION POSTOVULATORYFOLLICLES ELASMOBRANCH POSTOVULATORYFOLLICLES HAGlSH POSTOVULATORYFOLLICLES TELEOST POSTVITELLOGENICOOCYTES AXISFORMATION POTASSIUMSODIUMPUMP PREFOLLICULARCELLS PRE '6"$ PREVITELLOGENICFOLLICLES ELASMOBRANCH PRIMARYENVELOPE PRIMARYENVELOPE HAGlSH PRIMARYENVELOPE LAMPREY PRIMARYENVELOPE REMNANTS PRIMARYFOLLICLE HAGlSH PRIMARYGROWTH PRIMARYOOCYTE PRIMORDIALFOLLICLE PRIMORDIALGERMCELLS PRIMORDIALGERMCELLS MIGRATION PROGESTERONE PROGESTERONEINELASMOBRANCHS PROGRAMMEDCELLDEATH PROPHASE)OOCYTES PROSTAGLANDIN&_ PROSTAGLANDINSINOVULATION PROTANDROUSHERMAPHRODITES PROTEASOMES PROTECTIONFOREGGS 3CORPAENIFORMES PROTEININCORPORATION PROTEINPHOSPHATE PROTEINSYNTHESIS ZONAPELLUCIDA PROTEINYOLK

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PROTEOLYSIS PROTEOLYTICCOMPLEXES PROTOGYNOUSHERMAPHRODITES 2 RECEPTORSFORSPERMATOZOA RECOVERYAFTERSPAWNING REGULATIONOFSTEROIDOGENESIS REPRODUCTION RHYTHM RIBOSOMES RUPTUREOFFOLLICLE RUPTUREOFFOLLICLE LAMPREY 3 SEALS EGGCAPSULE ELASMOBRANCH SECONDARYENVELOPE SECONDARYENVELOPE COATING SECONDARYENVELOPE FORMATION SECONDARYENVELOPE LAMPREYEGG SECONDARYENVELOPE ORNAMENTATION SECONDARYLYSOSOMES SECONDARYOOCYTE SECRETORYTUBULE OVIDUCTALGLAND ELASMOBRANCH SEMINALRECEPTACLE TELEOST SEXREVERSAL SHELLGLANDINVIVIPARITY ELASMOBRANCH SHELLGLAND OVIDUCT ELASMOBRANCH SHELLHARDENING SHELL HAGlSHOOCYTE SITEOFOVULATION SKIN ABSORPTIONINVIVIPARITY SMOOTHMUSCLEINPOSTOVULATORYFOLLICLES SMOOTHMUSCLE THECAL SOMATICMESODERM SOMATICPREFOLLICULARCELLS SPECIALTHECALCELLS SPECIAL THECAL CELLS IN POSTOVULATORY FOLLICLES MICROPYLE SPERMATTACHMENT SPERMBINDINGSITE SPERMDEPOSITION TELEOST SPERMENGULFMENT SPERMENTRYSITE SPERMENTRY LAMPREY SPERMGUIDANCE SPERMORIENTATION LAMPREY SPERMPENETRATION SPERMPOCKETS TELEOST

SPERMRECEPTOR SPERMREJECTION SPERMRETENTION TELEOST SPERMSTORAGE SPERMSTORAGE OVIDUCTALGLAND ELASMOBRANCH SPERM ASSOCIATEDCELLS TELEOST SPERMATOGONIA SPERMATOPHORE ELASMOBRANCH SPERMATOZOA SPERMATOZOA AGGLUTINATON SPERMATOZOA STURGEON SPERMATOZOA SUPERNUMERARY SPERMATOZOA TELEOST SPERMATOZOON PENETRATION SPINNERETS OVIDUCTALGLAND ELASMOBRANCH SPLANCHNICMESODERM STAGESOFOOCYTEDEVELOPMENT STAGESOFOVARIANMATURITY STAGESOFPOSTOVULATORYFOLLICLE STEROIDPRODUCINGCELLS INNERVATION STEROIDOGENESIS STEROIDOGENESISDURINGATRESIA STEROIDOGENESISINFOLLICULARCELLS STEROIDOGENESISININTERSTITIALTISSUE STEROIDOGENESISINOVARIANFOLLICLES STEROIDOGENESISINPOSTOVULATORYFOLLICLES STEROIDOGENESISINTHECALCELLS STEROIDOGENESIS CICHLID STEROIDOGENESIS CYCLOSTOMES STEROIDOGENESIS ELASMOBRANCH STEROIDOGENESIS FOLLICULAR STEROIDOGENESIS GUPPYFOLLICLE STEROIDOGENESIS TELEOST STEROIDOGENESIS THECA STEROIDOGENICPATHWAY STEROID PRODUCINGCELLS STIGMA STROMA LAMPREYOVARY STROMA OVARIAN SUBFOLLICULARSPACE SUPERFOETATION SUPERNUMERARYSPERM SURFACEPITS SWELLINGOFEGGS SYNAPTICMEMBRANESPECIALIZATIONS SYNAPTONEMALCOMPLEXES SYNCHRONOUSOVARIES SYNGNATHIDOVARIES

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4 TANNING EGGCAPSULE ELASMOBRANCH TAXONOMICKEYBASEDONMICROPYLES TELOLECITHALEGGS TENDRILS EGGCAPSULE ELASMOBRANCH TERMINALZONE OVIDUCTALGLAND ELASMOBRANCH TERTIARYENVELOPE TESTOSTERONE TESTOSTERONEINFEMALEELASMOBRANCHS TETRADCHROMOSOMES THECA THECAEXTERNA THECAFOLLICULI THECAINATRESIA THECAINTERNA THECAINTERNAINATRESIA THECAOFCORPUSLUTEUM THECA CICHLID THECA CONTRACTIONS THECA ELASMOBRANCH THECA HAGlSH THECA HAGlSHFOLLICLE THECA HORMONES THECA LAMPREY THECA POSTOVULATORYFOLLICLES THECA POSTOVULATORYFOLLICLES HAGlSH THECA SEROIDOGENESIS THECA TELEOST THECALCELLSINATRESIA THECALCELLSINPOSTOVULATORYFOLLICLES THECALDEGENERATION LAMPREY THECALSTEROIDOGENESIS LAMPREY TIGHTJUNCTIONSINFOLLICULAREPITHELIUM TIGHTJUNCTIONS FOLLICULARCAPILLARIES TIGHTJUNCTIONSPERITONEALCELLS TISSUEBARRIERSINAPLACENTALYOLKSACVIVIPARITY TRANSCRIPTION TRANSCYTOSIS TRANSCYTOSISINFOLLICULARGESTATION TRANSCYTOSISINLUMINALGESTATION TRANSFEROFNUTRIENTS TRANSIENTYOLKSPHERES TRANSOSOMES TRANSPORTINFOLLICULARGESTATION TRANSPORTOFEGGS TRANSPORTOFIONS TRANSPORTINGEPITHELIUMINTROPHOTAENIAE TROPHICPATTERNSINVIVIPARITY TROPHODERMY TROPHONEMATA ELASMOBRANCH

TROPHONEMATOUSCUPS SHARK TROPHOTAENIAE TROPHOTAENIALABSORPTIVECELLS TROPHOTAENIALAPICALCANALICULARSYSTEM TROPHOTAENIALEPITHELIALCELLS TROPHOTAENIALPAVEMENTCELLS TROPHOTAENIALPAVEMENTEPITHELIUM TROPHOTAENIALPLACENTA TUBULARAGRANULARENDOPLASMICRETICULUM TUBULARGLANDS OVIDUCTALGLAND ELASMOBRANCH TUBULARMITOCHONDRIALCRISTAE TUNICAALBUGINEA TUNICAALBUGINEA TELEOSTOVARY 5 UMBILICALARTERY UMBILICALCORD UMBILICALSTALK UMBILICALVEIN UREAINEMBRYOTROPH URINARYDUCT CYCLOSTOME URINARYSINUS CYCLOSTOME URINOGENITALPAPILLA URINOGENITALPAPILLA CYCLOSTOME UROGENITALSINUS ELASMOBRANCH UTERINECOMPARTMENTS ELASMOBRANCH UTERINEMILK ELASMOBRANCH UTERUSINVIVIPARITY ELASMOBRANCH UTERUS ELASMOBRANCH UTERUS ELASMOBRANCH OSMOTICENVIRONMENT UTERUS GRAVID OVIPAROUSSKATE 6 VASCULARBULBSINFOLLICULARPLACENTA VASCULARBULBSINMATROTROPHICPLACENTA VASCULARIZATION FOLLICULAR VEGETALPOLE VESICULARTRANSPORTINLUMINALGESTATION VESTIBULE VILLIOVARIALESINLUMINALGESTATION VISCERALMESOTHELIUM OVARY VISCERALPERITONEUM OVARY VITELLINEARTERY VEIN VITELLINEBODY VITELLINEENVELOPE VITELLINEENVELOPEINATRESIA VITELLINEENVELOPEINOVULATION VITELLINEMEMBRANE VITELLOGENESIS VITELLOGENESISINMATROTROPHICTELEOST

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VITELLOGENESIS EARLY VITELLOGENESIS ELASMOBRANCH VITELLOGENESIS STINGRAY VITELLOGENIN VITELLOGENIN ELASMOBRANCH VIVIPARITY VIVIPARITY COELACANTH VIVIPARITY ELASMOBRANCH VIVIPARITY ELASMOBRANCH APLACENTAL OOPHAGOUS VIVI PARITY VIVIPARITY ELASMOBRANCH APLACENTALVIVIPARITY VIVIPARITY ELASMOBRANCH APLACENTALYOLKSACVIVIPAR ITY VIVIPARITY ELASMOBRANCH PLACENTALVIVIPARITY VIVIPARITY ELASMOBRANCH TYPES VIVIPARITY TELEOST VIVIPARITY TROPHICPATTERNS 7 WITHDRAWALOFMICROVILLIATOVULATION 9 YOLKDROPLETS FUSION YOLKGRANULES YOLKMASSINATRESIA YOLKNUCLEUS YOLKPLATELETS YOLKPOLYPEPTIDES YOLKPRODUCTION YOLKPROTEINPRECURSORS EXOGENOUS YOLKPROTEINS HYDROLYSIS YOLKSACINLUMINALGESTATION YOLKSACPLACENTA YOLKSACPLACENTA COELACANTH YOLKSACPLACENTA ELASMOBRANCH YOLKSACPLACENTA SHARK YOLKSAC ABSORPTIONINVIVIPARITY YOLKSAC BLUESHARK YOLKSAC SHARK YOLKSPHERES YOLKSTALK SHARK YOLKSYNCYTIUM SHARK YOLKVESICLES YOLK FORMATION YOLK SPECIlCMARKER YOLKYINCLUSIONS TYPES : ZONAPELLUCIDA ZONAPELLUCIDAINFOLLICULARGESTATION

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ZONAPELLUCIDAINFOLLICULARPLACENTA ZONAPELLUCIDAINVITELLOGENESIS ZONAPELLUCIDAINVIVIPAROUSELASMOBRANCH ZONAPELLUCIDAINVIVIPAROUSPOECILIIDS ZONAPELLUCIDA COMPACTION ZONAPELLUCIDA COMPOSITION ZONAPELLUCIDA CONVERSIONTOCHORION ZONAPELLUCIDA ELECTRON DENSELAYER ZONAPELLUCIDA FORMATION ZONAPELLUCIDA FORMATION ELASMOBRANCH ZONAPELLUCIDA HAGlSH ZONAPELLUCIDA INITIALAPPEARANCE ZONAPELLUCIDA LAMPREY ZONAPELLUCIDA LAYERING ZONAPELLUCIDA STURGEON ZONAPELLUCIDA SURFACERIDGES ZONARADIATA ZONATIONOFOVIDUCTALGLANDS ELASMOBRANCH ZYGOTENESTAGEOFPROPHASE)

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