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Fishery Bulletin 93(1). 1995 



pad. Drawings were made with a dissecting scope 

 and camera lucida attachment of live, anesthetized 

 larvae before they were preserved in 80% ethyl alco- 

 hol (ETOH). To determine laboratory shrinkage 

 rates, the larvae were remeasured after at least one 

 month in ETOH, and preserved lengths were com- 

 pared to those of the previous, live measurements. Since 

 larvae were drawn from living specimens, no staining 

 or special preparations were required for observation 

 of spines, rays, or other details of morphology. 



Results 



Pigmentation and overall development 



Daily measurements and developmental milestones 

 are presented in Table 1. The pelagic eggs were 

 spherical, averaged 0.96 mm diameter, had a single 

 oil globule, and hatched in 22-24 hours at 27°C. Eggs 

 were essentially transparent, the only pigment ob- 

 served was a series of small chromatophores on the 

 dorsal surface of the embryo (Fig. 1A). After hatch- 



Figure 1 



Early developmental stages of yellowtail snapper, Ocyurus 

 chrysurus, illustrated from live specimens. (A) late embryo egg, 

 0.96 mm diameter; (B) 2.23 mm SL newly hatched larva; (C) 

 3.36 mm, 3 days posthatch. Dark arrows indicate location of yel- 

 low chromatophore. 



ing and through the two day yolk-sac stage, larvae 

 possessed a single unpigmented oil globule in the 

 anterior end of the yolk-sac, an unpigmented finfold, 

 and 24 myomeres. Within 12 hours after hatching 

 (Fig. IB), the dorsal chromatophores of the embryo 

 had migrated to form a series along the ventral sur- 

 face of the body and tail; a single stellate chromato- 

 phore was present on the gut anterior to the anus, 

 and a light scattering of dark pigment was found on 

 the yolk-sac and lateral surfaces of the head. Exog- 

 enous feeding coincided with development of eye pig- 

 mentation, functional jaws, and gas bladder infla- 

 tion at 3.36 mm (age 3 days, Fig. 1C). Pigmentation 

 at this stage included a large dark chromatophore 

 on the ventral surface of the gut, four chromatophores 

 over the dorsal surface of the gut and gas bladder, 

 and a single, dark chromatophore on the ventral tip 

 of the notochord. In live specimens at this stage, we 

 first observed the development of a yellow chromato- 

 phore (indicated by arrow on Fig. 1C) located on the 

 lateral surface of the body at about midgut. Larvae 

 3.67-3.82 mm (Fig. 2A) showed dramatic develop- 

 mental changes. The development of numerous yel- 

 low chromatophores (indicated on illustrations by 

 solid arrows) scattered on the lateral surfaces 

 of the head, gut, and upper body near the base 

 of the pectoral fin, as well as dark stellate chro- 

 matophores on the hindbrain and on the ven- 

 tral edge of the cleithrum coincided with erup- 

 tion of the pelvic fin buds and the appearance 

 of preopercular spination. Larvae 4. 10^.53 mm 

 (Fig. 2, B-D) were characterized by daily in- 

 creases in the number of dorsal spines and by 

 elongation of the pelvic fins, as well as by an 

 increase in the density of yellow chromato- 

 phores on the lateral head region. Notochord 

 flexion occurred when larvae reached 4.40 mm 

 at 15-16 days posthatch (Fig. 3A) and was fol- 

 lowed by full fin formation. Changes in pigmen- 

 tation consisted primarily of increasingly dense 

 concentrations of yellow pigment on the lateral 

 upper body and head, dark web-like pigment 

 in the membranes of developing fins, and dif- 

 fuse internal pigment over the gut surface (Fig. 

 3B). The first indication of adult coloration was 

 visible on early juveniles approximately 14.00 mm 

 SL (Fig. 3C) where yellow chromatophores formed 

 a horizontal line through the eye onto the snout 

 and were also interspersed with the dark chro- 

 matophores lining the dorsal and ventral mar- 

 gins of the body at the fin bases. Yellow pigment 

 was also present along the lateral midline of the 

 tail. Near-adult pigmentation was present by 

 16.00 mm (age 62 days) at which time juveniles 

 were fully scaled (Fig. 3D). 



