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Vol. 4S, No. d
<br />ay I, !hour, I.$
<br />Sparc!ftt and yoik
<br />antmal pole aai
<br />Water-htir+denod
<br />~vity than water.
<br />ve, ova adl>Cr;~
<br />hours (Ftg, ZA):
<br />stumeres traas-
<br />rrn tot;il diaute-
<br />: diallr-gtriahxble
<br />:ithal, cleavage
<br />adhc~ive. A?~,1
<br />~:Us to whiten
<br />~ecaraes yc~Ilow
<br />neut.
<br />boars; second
<br />mately 1.0 mm
<br />hours; third
<br />1.2- by fl.S-nun
<br />h<~tus~ FourtL
<br />i hours; fifth
<br />~ hours; sixth
<br />routs: savie-tth
<br />(rnorula); no
<br />25 j~crce:nl of
<br />(rtrarula), 14
<br />halite; hlasto-
<br />td yolk ttta~
<br />dace. 87asto-
<br />r towarc] Im-
<br />ACI.
<br />g- 1G), Indi-
<br />:ace;pt with
<br />. 6IaSOrxlGtzn
<br />surfaet; Rat;
<br />spherr; tm
<br />~laslocIerm),
<br />r (Fig, 1D).
<br />sphere and
<br />~CSt'rtt. Peri-
<br />pcrlphe~ry
<br />tri of inner
<br />Yoh sac to
<br />-um hlasto-
<br />grog b•osn
<br />pherc.
<br />
<br />1}eccoiher 1y82 Mtxctrrxv, Gt?aTAr+SOx; RnzURnAC$ SUCKhA DEVt:LOPMSS~rer 555
<br />StaJ,,ls 12: early gastrula, 34 hours (1~'ig. IE),
<br />Urtdetrittt of blaetodiac thickmtod bo form
<br />"rrrndrottlst" or mart,~;paI ridge with tiaaec
<br />layer t6ctned the germ ring. Ring l6ickeat
<br />ptrstarioriy, recognized as embryonic shield.
<br />Prt,~sun-ptive tatttoclcrresl cells at postexior
<br />alga of shield begitttling to i>tvolgte through
<br />blastvliare altd spread 6eue•atlt bkstoderm,
<br />Cells of precJtordel plate and notochord mi-
<br />g~rnting inward over dorsal lJp of blastoporc
<br />(eaablishment of embryonic axis). P~np-
<br />tit+e mesocIQrmsl cello also ~~ inward,
<br />p~tioned eitbcr mde of embryonic asas ba
<br />aea3t ectoderm and above ~dcderm. Pcri-
<br />6fast, +as<dwutst cx11s, and germ ring cells tmt
<br />mvolt-cxl in involution sprerd over 50 ptxoent
<br />of yolk sphere.
<br />SCige 13: midrDe l,+astrula, 35 hours. Iir
<br />vagination lcngtheAing embryonic ahicld;
<br />bL•rsEoprrre marks posterior aids of embryo.
<br />shlgr: 14: late gastrulas 38 boom (Fig. ~
<br />Err-bryonic shield nearly reaching animal
<br />pvk of egg on tbrsal rrteridiaa; shield ap-
<br />proximately 1.3 tmn ~; cxntcet-tratios- of
<br />invaginated cells clearly visJ"ble at anterior
<br />end of SIticlcl; ~andtvuTxt ce1Ls and germ ring
<br />cdh, acx:onr~nlcsi3 by presurnpliva ectnckr-
<br />mal culls, forming outwardly ay epiblast:
<br />marginal ridge sltil~~~d below equator of egg:
<br />tawovered pariton of }rolk protrrxlea as yolk
<br />Plo6•
<br />Stage 15: Orly ncurula, d5 hvuis, 1.B mm
<br />diameter. 131astopara closed; yolk plt~ ~
<br />logger protruding. lrrnbryonie Shit:W stpprox-
<br />imttely £.0 mtn laug, circumscribing 75 per-
<br />cxwt of egg, overlying }rolls sac. Neura! pkte
<br />forinexl, rotator and anterior margins nbt
<br />etsarly tlelimitecl, Idotaehord in form of ridge
<br />iuessing into yolk, ]aloral acrtctcttord rtrdl-
<br />rocrtt nut clearly segarale[1 Er-om sheets aE
<br />meytadem~.
<br />5tagtt 18: late Itcluula, 47 l~attts (Fig. 1G).
<br />Neural ka:l remains 2d nuir long, cir+cupM1_
<br />-.~I'ibirtg T5 per<~nt of egg. Neural plate aon-
<br />traotcd, more deFined aloi~ tdges• Cephalic
<br />region arrow shaped ;a dorsal view: eye rudi-
<br />ments forming; ~tual ri[~es as folds on ed-
<br />~+' side of actual plate. Notochord ,epa-
<br />rated frtuu mr~sodl:rm.
<br />Stage 17; eye nldiroents„ dtry 3, 49 hoaua,
<br />embryo length 2.0 mrq. 13rain cavities nerd
<br />spinal cord formal by eo~Mractiotr of aeural
<br />plate, ~'e rudltnents as latarrl protrusions at
<br />[C ~Cl
<br />91~
<br />/ E .f~-
<br />
<br />- _~
<br />• '~ •
<br />-
<br />f.
<br />•
<br />y,
<br />~
<br />..
<br />J f• s~
<br />~M ;
<br />~ •
<br />f~ ;
<br />
<br />r
<br />•
<br />f
<br />at
<br />i ~ ~' 3
<br />Y .
<br />F r LiSC.-S'*d~lC one,
<br /> 6r i ti •
<br />
<br /> y •` i
<br /> ~ .~
<br />.,
<br />oorse~
<br />'l •• n0
<br />tat Mal
<br />.:
<br />rr ~
<br />A,[Mle (ill ru Fa Yt'- 'f poet.
<br />G .r
<br />. •r "
<br />f
<br />.~
<br />~.
<br />''~•~ ~:
<br />',
<br />~, 75
<br />Dersaf _
<br />Fig. I- 13arly ambeyolog'met alages rE rtaurbsck R~k•
<br />er, XgraaeJsrrn sesattt~ elfauson remoeed is ell 1tu1 A.
<br />I.e~nmd: AIP = ontarinr Mtertiasl poWai, Ant, ~ u~6e•
<br />trot, AA a anditorY plaeacle, Bl ~ hlavlocit.Tm. Hk
<br />blastocael, libn = bb~r~rtere, DP ~ blartopore, Ch =
<br />ehuriorr. LS ~ enrbryraolo shield. [;R ~ gnrm ring, FIF
<br />= head fold, LFM ~ ~t~al prate mL•sodarm, Moe =
<br />masenCepF>el~, iNR rnargirktl ridge, NF = nnnrrl
<br />faki, NK ~ neural kcet, NP =neural plate. t?F a optic
<br />placade, Pb = per#thst, PM ~ perivi6clls+e rr-eYaGraae.
<br />~ ~ r~-e s~paice, Rb ~ rhmnlnsneeplmloo. tom
<br />som~lea, Y a Yoh p~&• ~ YS =Yolk ~rx
<br />anteritsr end of hraia. Proscncephalon (fore.
<br />brain), mesCltCCphalon imidbrain) and rllomb-
<br />e»eephalon (lrirrdbrain) distinguishable, Audi-
<br />MAY-14-97 WED 1227 FISHERY ~ W11.DI iFF Rl(l i:Ax N[1. 47na41Rn4t F_ n.~
<br />
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