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Fishery Bulletin 92(2). 1994 



pigmentation and were difficult to count on dolphin- 

 fish larvae; however, a 5.5-mm pompano dolphin had 

 33 myomeres and a partially cleared 11-mm common 

 dolphin had 30 vertebrae. Only two pompano dol- 

 phin between 6.1 and 9.7 mm were collected (7.5 and 

 8.5 mm) and morphometries for these larvae were 

 considerably smaller than for the other specimens 

 (Table 1). 



Pigmentation 



Dolphinfish were heavily pigmented at all sizes, ex- 

 cept the caudal peduncle and its finfold in early 

 preflexion larvae of common dolphin which was 

 unpigmented (Fig. 1). In common dolphin <4 mm, 

 the length of the unpigmented portion of the cau- 

 dal peduncle was 15-20% SL. By 4.5-5.0 mm, how- 

 ever, pigment was present along the caudal peduncle 

 and on the caudal finfold (Fig. 1). Early preflexion 

 pompano dolphin <4 mm had a row of melanophores 

 along the caudal peduncle (both dorsally and ven- 

 trally) and pigment was scattered throughout the 

 caudal finfold (Fig. 2). On the head, pigment was 

 scattered externally over the premaxilla, snout, and 

 fore-, mid-, and hind-brain of early larvae of each 

 species. Pigment also was present along the dentary, 

 lower jaw, isthmus, branchiostegal rays, and on the 

 roof of the mouth. On the visceral mass, melano- 

 phores were scattered over the foregut and anus of 

 early preflexion larvae of both species but the hind- 

 gut was sparsely pigmented laterally (Figs. 1 and 

 2). Gut pigmentation increased with length. Verti- 

 cal bands of pigment first formed along the dorsal 

 and anal fins of common dolphin at about 8 mm. 

 These bands of pigment subsequently extended 

 across the body; 12 to 13 poorly formed bands were 

 visible by 10 mm. Vertical bands became more dis- 

 tinct as larvae grew (Fig. 1). Bands of pigment do 

 not form in pompano dolphin, but this species does 

 have a row of enlarged melanophores along the body 

 dorso- and ventro-laterally (adjacent to the dorsal 

 and anal fin bases) by 7.5 mm, which was not 

 present in common dolphin (Figs. 1 and 2). 



Pectoral buds were present on early larvae of each 

 species. Pigment was scattered over the pectoral 

 axilla and was heavier on pompano dolphin than on 

 common dolphin of similar length. The proximal 

 portion of the upper pectoral rays of common dol- 

 phin was pigmented by 14-15 mm; no pigment was 

 present on the pectoral rays of pompano dolphin. 

 Dorsal- and anal-fin bases were thickening by 5 mm 

 in pompano dolphin and by 6 mm in common dol- 

 phin; the anal-fin base developed slightly before that 

 of the dorsal base. Both fin bases and their ray an- 

 lagen developed in a posterior to anterior direction. 

 Pelvic-fin buds of common dolphin were present by 



6.5 mm and pigmented by 7.5 mm. No pompano dol- 

 phin between 6.1 and 7.5 mm were examined, but 

 the pelvic buds were present by 7.5 mm. The pelvic 

 rays of pompano dolphin remained unpigmented at 

 all sizes. Pigment occurred on the developing cau- 

 dal rays of each species by early flexion. By 10 mm, 

 all but the distal tips of the caudal rays were pig- 

 mented in common dolphin; only about the proximal 

 third of each caudal ray was pigmented in pompano 

 dolphin. Differences in caudal-fin pigmentation were 

 more pronounced as larvae grew (Figs. 1 and 2). 



Head and body spination 



Dolphinfish larvae developed two series of pre- 

 opercle spines, one series along the posterior mar- 

 gin of the inner shelf and the other along the outer 

 shelf. Number and location of spines along the outer 

 shelf of the preopercle separate larval common dol- 

 phin from pompano dolphin. Two spines were 

 present along the margin of both the inner and outer 

 preopercular shelves of 4-mm common dolphin, the 

 largest spines occurring on either side of the angle 

 of the preopercle (Figs. 1 and 2). A third spine was 

 added along both the inner and outer shelf by 7 mm; 

 a fourth spine was added along the outer preopercle 

 by 10.0-10.5 mm. A total of three spines occurred 

 along the inner and four spines along the outer shelf 

 of the preopercle of larval common dolphin (Fig. 1). 

 Arrangement of preopercle spines in larval pompano 

 dolphin <4 mm was similar to that in common dol- 

 phin except three rather than two spines were vis- 

 ible along the outer preopercular shelf. A third spine 

 was added along the inner shelf by 7 mm and a 

 fourth and fifth spine along the outer shelf by 9 mm. 

 A total of three spines occurred along the inner and 

 five spines along the outer preopercular shelf of lar- 

 val pompano dolphin (Fig. 2). Number and place- 

 ment of preopercle spines were consistent through 

 at least 15 mm in both species. All preopercle spines 

 were simple (Figs. 1 and 2). 



Dolphinfish have several spines and ridges on the 

 head. The pterotic area was swollen in both species 

 by 5 mm and a laterally directed spine was present 

 along the supraorbital ridge of each frontal bone of 

 6-mm pompano dolphin and 7-mm common dolphin 

 (Figs. 1 and 2). The supraorbital ridge of each spe- 

 cies usually had a single spine, but some pompano 

 dolphin had two or three spines along the ridge. The 

 swollen pterotics and supraorbital spine were best 

 observed when specimens were viewed dorsally; 

 both features were well developed by 7.5-8.0 mm. 

 The frontal bone was notably thicker above the eye 

 of pompano dolphin, but the supraorbital ridge was 

 less well developed in pompano dolphin than in com- 

 mon dolphin by 9.5 mm. The supraorbital spine(s) 



