APRIETO: EARLY DEVELOPMENT OF FIVE CARANGID FISHES 



by Hildebrand and Cable (1930) who also studied 

 the abundance and distribution of the young up to 

 50 mm taken from the coastal and offshore waters 

 of Beaufort, N.C. In addition, life history series 

 were described for two species of Decapterus from 

 the Indo-Pacific region: D. russelli by Vij- 

 ayaraghavan (1958) andD. maruadsi by Shojima 

 (1962). The latter series is quite similar to that of 

 D. punctatus. 



Distinguishing Features 



Larvae of D. punctatus are decidedly deep- 

 bodied although the adults are the most slender of 

 all carangids. The head has a supraoccipital and 

 an orbital crest and preopercular spines. During 

 metamorphosis, the ultimate rays of the dorsal 

 and anal fins become separated and modified into 

 finlets. The first interhemal spine is slightly swol- 

 len. Together with the hemal spine of the first 

 caudal vertebra to which it is closely apposed it 

 forms a strong brace at the posterior border of the 

 abdominal cavity. There are 25 vertebrae — 10 

 trunk plus 15 caudal. D. punctatus is one of the 

 few carangids with a vertebral count of 25, the 

 usual number being 24; this is a useful character 

 for separating the larvae from other species of 

 Decapterus. Berry (1968) used the scales, scutes, 

 and lateral line spots in the identification of the 

 older juveniles from 90 mm long. These characters 

 are not yet formed in the larvae. 



Morphology 



Body depth decreases relative to standard 

 length and is 30.6 to 35.4% during the entire lar- 

 val period (Table 6). In transforming larvae and 

 early juveniles, body depth decreased to 28%. The 

 head is long and deep; relative head length in- 

 creases throughout the larval and juvenile stages. 

 It is 27% in the smallest larvae (3.0 mm) and 

 attains a maximum of 35% in the larval period. In 

 transforming larvae and early juveniles, it is 

 never less than 31% of the standard length. The 

 head is deeper than long in the early larval stages 

 up to notochord flexion and ranges from 108.3 to 

 113%. Thereafter, head depth decreases gradually 

 with an average of 90% but is never less than 80% 

 of the head length in the early juveniles. A supra- 

 occipital crest is present during the larval period 

 but is resorbed at metamorphosis. The snout is 

 slightly concave in the youngest larvae (3.0 mm), 

 but becomes straight at initial notochord flexion. 



In older and transforming larvae, the snout de- 

 velops a convex profile. 



The eyes are large and round, and the orbit 

 diameter increases relative to head length. Eye 

 index ranges from 30 to 46.1% during the larval 

 and transition periods and is highest at notochord 

 flexion. A low orbital crest bearing a weak spine is 

 present above the eyes in larvae 3 to 7 mm long. In 

 older larvae, the crest is gradually resorbed and is 

 no longer visible at 10 mm. 



Marginal and lateral surface spines are present 

 on the preopercle. They increase in size and 

 number during the larval period but are gradually 

 resorbed at metamorphosis. At 17 mm, the lateral 

 surface spines are gone and the margin spines are 

 reduced to fine crenulations on the preopercular 

 margin. 



The slender gut is coiled in a single loop in the 

 early larvae. A second loop is formed at transfor- 

 mation and a third is added in the early juveniles. 

 Snout-to-anus distance increases relative to stan- 

 dard length; it is 52.3 to 59.5% of the standard 

 length during the entire larval and transition 

 periods and does not change noticeably during the 

 early juvenile stages. Hypaxial muscles begin to 

 develop around the gut in 5-mm larvae, and at 7 

 mm, the abdominal cavity is completely enclosed 

 except at the anal opening of the gut. 



The first scales to ossify are those at the post- 

 erior region of the lateral line in juveniles 17 mm 

 long. Ossification of the lateral line scales pro- 

 ceeds anteriad and the full complement of scales 

 and scutes is present at 20 mm when the body 

 scales are formed. 



Pigmentation 



Chromatophores are slow to develop in the lar- 

 vae and remain sparse until the early juvenile 

 stages. There are a few melanophores on the back 

 of the head, on the jaws, and infrequently on the 

 snout and cheeks. As in other carangid larvae, 

 there is a row of melanophores on each side of the 

 bases of the dorsal and anal fins, along the lateral 

 line at the caudal region, and on the dorsal wall of 

 the peritoneum. Compared to those of Seriola 

 zonata and Elagatis bipinnulata, the larvae of 

 Decapterus punctatus are pale. Melanophores are 

 not profusely developed until metamorphosis, and 

 they are mostly located above the midline. In the 

 early juveniles, iridiophores spread all over the 

 body but are most dense below the lateral line, 

 giving the fish a metallic sheen. 



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