7006

• UCREFRP Catalog Number: 7006
• Author: Gustafson, E.
• Title: Early Development, Adult Sexual Dimorphism, and Fecundity of the Razorback Sucker,
• USFW Year: 1975
• Copyright Material: NO

salvas on either side O~ ~n8 dill0ryoaic ~~ls beneath the ac~oderm SLId
aQove Lhe endoderm.
.l:'e l' 1 olast, raL.dwulsl.- eel: s 8..r'1.d geri~ ring cells hO: iLl.-liol ved in
involu'c ion i1ave epi bolateu. 0\1 er ~ the yoi~ spc.ere.

Stage 1): Mid~le Gas~r~la:

J 5 ilr.

(F'ig. 2e).

Invagination has lellgcheiled the embryonic shield.. The blasto-
pore marks the p0s~crior axis 0; the embryo.
The blastoderm still covers only ~ of the yolk sphere.
Stage 14: Late Gastrula: J6 hr. (Fig. 2e).
On the d.orsal r.e:r:idiaH, the embryol.l ~ shield neal."ly reaches the
aLlimal pole oii,;!!e egg: s~.li81d is app:cOX. 1. J IlliIl lo~l.g. .8. coacentra-
tiOLl of i.Gvagi.aa.;eli mate.cial il~c.;..Y cle6l.r::"j oe seen at the anterior end
of t.i"le shield. rtCJ.-ild.-,'o'ulst cells dI.l.d germ riLlg cells, accOffipanled by
pr8su~ptlve ~c~o~ermal cells, are epibolating to cover the yolk mass

out~aru.lJ ~s epiblas~.

The ma.rgi.Llb.l l'idge bas sllifted.. well below the equa.tor of tild
egg; a.nd, an ul.l.coveredFortion of yuLe: p:cotruc.es as a yolk plug..
6i..~ge 1 j: .ca.rl.y .NeUl'ULi: 45 lu'; 1. G ;;:..1'U d.ia.

- .

'j:r.e blastopore is now cloSdd. '1':.8 'yol~ plug no longer pro~rud.-
es. the embr.;.;olli~ si1ielu. is approx. 2..0 mIi.1 lO!le;" a.(.LJ. clrcu3scrloes
aiJout ! of the egg overl:,U:i.f'; the yolk sac. A thickening of ectodarm,
the neural plate, has fO:Cili,:~d but its ldi:.eral and anterior margins are
HO:'; ,.:;le:arly delLnillat.ed.. the LlOt00ho:.:.\i is in the form of a ridge
which presses i~to the yolk; but, laterally the notochord rudiment is
1l0~ clearly sepaI'3.ted fr'o~a Lh8 slleats o:t mesoderm.
6tage 16: LSlte l\lt::ur"ula: .....7 hr. (fib' 2f).
'i'he neuI'dl t;....:.-.:;:I. is st ill about. 2. C mID long and circumscribes
~ oi' the egg. tb8 !leuru.l plat e has COii-t.rac t.ed and is more accurate-
ly deliwinated alon~ its td6~~. 1il~ cephalic region appears arrow-
Sl1[iped v/(lell viev;(;u [ruiG. above: e.ye .cud.L.aer.l.l..s are forming. 'I'he Lleur-
ai ~i~ges have formed as ioluG ~n ei~her side of the neural plate.

'lhe Ho~ochorJ. i8 !.I.U,'" ciepaLd,l,.;';J.

~ . .
11'lO~:: '"'.-.~ ~n.e.sO~_UI.m.

;j "CJ.6~ l?: ~y 8 hl....: L:"C;Ll t.. s: da.j J;

, -
-r;l .11';

2.:' lliLl (embryo length).

-'-~4--::" _"""""!"'""'" "i,"':o:;":"'-r~<-.--,-".' ;"'_';-""

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