Table 1. — Comparison of some important differentiating 

 characters in Hemilepidotus zapus and H. papilio. 



'Data are from Peden (1978); mean is followed by range in 

 parentheses. 



larvae \sH. zajms, while the 13.7 mm SL larva lacks 

 urostyle pigment and is probably H. jordani 



Early larvae of H. zajms (6.5-17.0 mm SL) were 

 linked together by the presence of melanophores 

 above and below the urostyle (Figs. IC, 2); such 

 melanophores are lacking in all other known 

 Hemilepidotinae larvae. Larvae undergoing noto- 

 chord flexion can be distinguished from H. hemilepi- 

 dotus by the lack of external pigment along the 

 posterior body and from H. jordani by the presence 

 of ventral midline pigment which curves up toward 

 the urostyle (Fig. 1). 



After notochord flexion and through the juvenile 

 period, counts of meristic structures as well as a com- 

 bination of adult characters (Peden 1978) will allow 

 separation of the three species. Postflexion larvae of 

 H. zapus have scales on the caudal peduncle that will 

 distinguish them from other, similar-sized Hemilepi- 

 dotinae larvae. These larvae also have a characteris- 

 tic notch in the first dorsal fin, between the third and 

 fourth spine, that is present in adults of all Hemi- 

 lepidotus except H. papilio (Fig. 2F). A summary of 

 some diagnostic features of all known Hemilepidotus 

 larvae is presented in Table 2. Larvae and juveniles 

 of H. papilio remain unknown. 



General Trends of Development 

 Pigmentation (Fig. 2) 



In the smallest larvae (6-7 mm SL), pigment ap- 

 pears on the head dorsally over the midbrain and on 

 the anterior forebrain. In larger larvae 7-9 mm SL, 

 additional pigment appears at the base of the hind- 

 brain, posterior to the eye and in the opercular area. 

 In postflexion larvae, head pigment increases. 



Separate pigment patches appear posterior to the 

 eye (usually about 5 or 6 spots) and on the operculum 

 dorsoposterior to the preopercular bone. Larvae 6-7 

 mm SL have pigment on the nape and on the dorsal 

 surface of the gut. Gut pigment increases laterally 

 with development, and in larger postflexion larvae it 

 becomes more internal than external. By 14-15 mm 

 SL, nape pigment extends ventrally to the dorsal 

 surface of the gut. 



There are five general areas of pigmentation in the 

 postanal region: 1) an external row (appearing 

 more or less double) of melanophores along the dor- 

 sal midline extending from the nape to the last 

 myomere; 2) a dorsolateral row of internal pigment 

 along the notochord, extending from the nape to 

 about the last 4-7 myomeres; 3) an external row of 

 melanophores along the ventral body midline from 

 midbody (about 1 1 myomeres after anus) to the last 

 myomere; 4) a ventrolateral row of internal pigment 

 along the notochord, beginning at about 4-6 myo- 

 meres after the anus and extending to about 6 or 7 

 myomeres from the end of the tail; and 5) a few ex- 

 ternal melanophores along the notochord in the 

 caudal peduncle area, and external melanophores 

 dorsal and ventral to the notochord at the posterior 

 tail tip. Prior to notochord flexion, at about 9.0 mm 

 SL, the anterior ventral midline pigment gradually 

 becomes more internal. In postflexion larvae, this 

 ventral midline row is comprised of < 10 melano- 

 phores beginning about 17 myomeres posterior to 

 the anus. By 16.7 mm SL, all the postanal pigment is 

 internal except for the dorsal midline melanophores 

 and a few spots in the caudal peduncle area. After 

 about 17 mm SL, melanophores in the caudal pedun- 

 cle are no longer visible. 



Morphology (Table 3; Fig. 3) 



Relative growth trends are summarized in Figure 

 3. Preanal length, head length, depth at pectoral fin, 

 snout to anal fin length, and snout length increase 

 with development. Eye diameter as a proportion of 

 head length undergoes a gradual decrease with 

 development. Depth at the caudal peduncle and the 

 length from the snout to dorsal fin origin increase 

 sharply with development in larvae about 16.0-19.0 

 mm SL and then decrease in larger specimens. 



Meristic Structures (Tables 4, 5) 



Branchiostegal rays have begun to ossify in our 

 smallest specimens (7-8 mm SL), and the adult com- 

 plement of six rays is completely ossified in larvae 

 ^ 12-13 mm SL. 



449 



