WATSON: DEVELOPMENT OF EGGS AND LARVAE OF WHITE CROAKER 



Figure 2.— Development of the Genyonemus Uneatus egg: a) 

 blastula stage, 0.78 mm diameter; b) gastrula stage, 0.86 mm 

 diameter; c) early embryo just prior to blastopore closure, 0.90 

 mm diameter; d) tail bud stage, 0.84 mm diameter; e) late 

 stage, 0.84 mm diameter. All illustrations are of live eggs. Note 

 that oil droplets are somewhat smaller than average in this 

 group of eggs. 



melanophores appear shortly thereafter. About 

 5 h after eye capsule formation (at 20°C) small 

 melanophores surround the trunk and are scat- 

 tered dorsally on the head (Fig. 2d). A few me- 

 lanophores occur on the yolk adjacent to the tail 

 bud at this stage. As development continues the 

 dorsal head pigmentation increases and trunk 

 melanophores become situated primarily dor- 

 sally and dorsolaterally. Yolk melanophores in- 

 crease in number until they nearly surround the 

 yolk just before hatching (Fig. 2e). 



The oil droplet is located opposite or adjacent 

 to the embryo through gastrulation (Fig. 2a, b). 



During the latter part of the egg stage the tail of 

 the developing embryo grows past the oil drop- 

 let, which ultimately is situated adjacent to the 

 embryo just anterior to the anus (Fig. 2e). 



Optic capsules develop almost simultaneously 

 with blastopore closure and just prior to somite 

 development. Lens development begins at about 

 the four myotome stage. 



Somite differentiation begins just behind the 

 head and continues posteriorly. Kuppfer's vesicle 

 first becomes apparent near the tip of the tail 

 bud at about the 4 somite stage and persists to the 

 18 somite stage. Heart and finfold development 

 are initiated at about the 18 somite stage and the 

 tail first separates from the yolk shortly there- 

 after. By the end of the egg stage the embryo has 

 25-26 myomeres, otic capsules with at least the 

 sagittae developing, a simple tubular gut, wide 

 finfold, and functional heart. 



Preserved eggs collected from the plankton at 

 1900 PST on 29 January 1979 were largely in the 

 two, four, and eight cell stages. Live eggs from 

 the same sample began gastrulation after 20-22 

 h of incubation (ca. 20°C) and eye capsules devel- 

 oped at about 26-28 h. The 18 somite stage was 

 reached at about 38-40 h and the full somite com- 

 plement attained by 43-45 h. All larvae had 

 hatched by 52 h. 



YOLK-SAC LARVAE 



Pigmentation 



The pigmentation of newly hatched larvae 

 closely resembles that of late stage eggs, with 

 melanophores concentrated primarily dorsally 

 and dorsolaterally on the head and trunk (Fig. 

 3a). Additional pigment includes a characteris- 

 tic large dendritic melanophore extending up- 

 ward from the nape to the margin of the finfold, a 

 large midventral melanophore about halfway 

 between the anus and tip of the tail (one or two 

 small lateral melanophores may occur here as 

 well), and one to three small middorsal and mid- 

 ventral melanophores near the tip of the noto- 

 chord. One or two melanophores usually occur 

 ventrally on the gut, near the anus. Oil droplet 

 pigmentation is mainly proximal. A few melano- 

 phores are usually scattered on the yolk sac. The 

 nape, oil droplet and gut, and midtail pigment 

 appears as three distinct bands in live larvae. 

 Only the nape and midtail melanophores may be 

 expected to survive prolonged Formalin preser- 

 vation. 



405 



