MILLER and SUMIDA: DEVELOPMENT OF CARANX MATE 



fin fold, but was lost in older larvae (ca. 7.5 

 mm SL). 



Following flexion of the notochord (ca. 6.0 mm 

 SL), melanophores were still evident along the 

 posterior margin of the hypural bones and along 

 the dorsal and ventral margins of the fin mem- 

 brane in the caudal peduncle region, with addi- 

 tional caudal fin pigment developing distally 

 between the rays. The density of melanophores 

 increased in the older larvae, generally forming 

 in one or two rows between the rays. 



PECTORAL.— Larvae of ca. 6.0 mm SL had 

 minute melanophores scattered along the distal 

 margin of the pectoral fin, but pigmentation 

 remained sparse compared to that of the caudal, 

 dorsal, and anal fins. By 8.5 mm, the pigmentation 

 had increased to rows of three to five melano- 

 phores interspersed between the more dorsal rays, 

 with this pigmentation spreading ventrad as the 

 larvae grew. 



DORSAL AND ANAL.— Pigmentation of the 

 dorsal fin fold was described earlier. In the early 

 larvae up to ca. 3.0 mm, there were dendritic 

 melanophores lining the edge of the preanal 

 fin fold which were lost in larvae by 4.5 mm. 



The pattern of pigment development was 

 similar for both fins, although that on the anal 

 was formed earlier. This was consistent with the 

 apparent earlier formation of the anal fin. By 

 6.0 mm, larvae displayed the beginning of a row 

 of melanophores along the distal margin of the 

 anal pterygiophores (Figure 3A). Initially each of 

 these melanophores was situated between ad- 

 jacent pterygiophores in the anterior portion of 

 the fin; more developed posteriad in older larvae. 

 The entire length of the proximal margin of the 

 anal fin had this pigment by 8.0 mm, but the 

 dorsal fin margin showed no evidence of it until 

 ca. 7.0 mm. Approximately three-fourths of the 

 anterior portion of the dorsal fin margin was 

 pigmented at 10.0 mm. 



Rows of two to four melanophores were evident 

 along the distal region of the fin membrane 

 between the anteriormost anal fin rays at ca. 

 6.0 mm. The fin pigmentation process proceeded 

 posteriad, with the melanophore number increas- 

 ing to as many as 14 in double rows between 

 rays in larvae of ca. 10.5 mm. 



Larvae of ca. 8.5 mm showed melanophores 

 forming distally on the fin membrane surrounding 



the dorsal spines and between the first few dorsal 

 rays. Subsequently, the fin pigment developed 

 posteriad as in the anal fin; and the density of 

 melanophores on the dorsal fin membrane was 

 similar to that of the anal fin by 11.3 mm. 



PELVIC (VENTRAL).— Like the pectoral fin, 

 each pelvic fin was sparsely pigmented. Two or 

 three melanophores were observed on the small, 

 rayless fin on larvae of ca. 6.0 mm. By ca. 7.6 

 mm, two or three rows of a few small, incon- 

 spicuous melanophores had formed between the 

 rudimentary fin rays (Figure 3A). 



Fin Development 



The omaka larvae hatched with no developed 

 fins but a broad, flat fin fold. The subsequent 

 formation of fins (first development of lepido- 

 trichia) followed a sequential pattern much like 

 that described for Trachurus symmetricus (Ahl- 

 strom and Ball, 1954), viz. caudal, pectoral, anal 

 and soft dorsal, spiny dorsal, and pelvic (ventral) 

 in that order. 



The stage of omaka fin development par- 

 ticularly, appeared to us to be more dependent 

 on size attained than age. Smaller, older larvae 

 were found to have not yet completed certain 

 stages, while some precocious (larger) larvae had. 

 Owing to rapid development of larvae, larger 

 samples at more frequent time intervals would be 

 required to test a hypothesis of size versus age 

 dependence of developmental events. 



Caudal 



Caudal actinotrichia could be observed in 

 larvae as small as 2.2 mm in the form of faint 

 lines projecting distally from the area around the 

 tip of the notochord. True rays (lepidotrichia) 

 were first evident in larvae ca. 3.4 mm (day 7) 

 and became more prominent in 4.0 mm larvae as 

 ventrally projecting incipient rays from the 

 presumptive hypural plate below the tip of the 

 notochord. These rays were well-defined in larvae 

 of ca. 4.5 mm (day 12), when notochord flexion 

 was initiated. At this time as many as 15 rays 

 of the total 17 principal caudal rays could be 

 observed still projecting obliquely from the 

 developing unossified hypural bones lying ventral 

 to the notochordal tip. Notochord flexion and the 

 formation of the 17 principal caudal rays (nine 



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