402 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



without rays. The oil globule is still visible, but 

 the yolk mass has been largely absorbed. Pig- 

 mentation is basically unchanged. Thickening 

 of the head and of the body anterior of the anus 

 is very noticeable. I believe the yolk-sac stage 

 ends at about this period of development. 



DEVELOPMENT FROM LARVAL TO 

 JUVENILE STAGES 



Development from about 3.5 to 110 mm. is 

 included as larval, early juvenile, and juvenile. 

 A developmental series is illustrated in figures 8 

 to 16. Each set of characters will be discussed 

 separately and development briefly outlined. 



DEVELOPMENT OF FINS 



Caudal. — A fully developed caudal fin has 14 

 principal raj's (of which 12 are branched) and 14 



Figure 8. — Larva, 3.7 mm 



Figure 9. — Larva, 4.0 mm. 



Figure 10. — Larva, 4.7 mm. 



Figure 11. — Larva, 5.3 mm. 



to 17 secondary rays. For details of caudal skele- 

 ton of M. curema, see Hollister 1937. 



At about 3.7 mm. total length (fig. 8) there is 

 no indication of development of the caudal fin 

 other than a deeper constriction of the finfold in 

 the caudal region. A thickening is evident on the 

 ventral side of the urostyle at about 4.0 mm. total 

 length, but no true rays have formed (fig. 9). At 

 about 4.7 mm. total length (fig. 10), 14 rays have 

 developed ventrally which will be the principal 

 caudal rayo, the urostyle has tipped upward, and 

 the fin shape has changed. The caudal has de- 

 veloped a well-rounded form at about 5.3 mm. 

 total length (fig. 11), the urostyle has reached its 

 maximum flexing, and about 23 rays are visible. 

 The fin is much broadened at about 7.0 mm. 

 standard length (fig. 12), and 25 or 26 rays are 

 present. A full complement of rays (14 principal 

 and 15 secondary) is visible at about 14.5 mm. 

 (fig. 13), although none of the principal rays are 

 branched ; and tlie fin has begun to fork. Branch- 

 ing of the 12 principal rays (2 principal rays do not 

 branch) has occured by 25 mm. standard length, 

 and forking seems complete by 110 mm. (figs. 14, 

 15, and 16). 



Dorsals. — When fully developed the first dorsal 

 has 4 spines, and the second dorsal has 1 spine and 

 8 branched rays. 



The dorsal bases are first evident and developing 

 raj's visible in both fins when the larvae are about 

 4.7 mm. total length (fig. 10). The 4 spines of 

 the first dorsal and the 1 spine and 8 soft rays of 

 the second dorsal are quite evident at about 5.3 

 mm. toial length (fig. 11). The last ray of the 

 second dorsal is branched by 14.5 mm. standard 

 length, 7 of the 8 soft rays are branched by 25 

 mm., and all are branched by 50 mm. Final fin 

 shape is reached when the juveniles are between 

 50 and 110 mm. long (figs. 13, 14, 15, and 16). 



Anal. — The fully developed anal fin has 3 

 spines and 9 branched soft rays. 



Developing rays and the anal base are first 

 evident in larvae about 4.7 mm. total length 

 (fig. 10). The full complement of rays (12) is 

 present in larvae about 5.3 mm. total length (fig. 

 11). The two spines are discernible and the last 

 ray has branched by a larvae size of about 14.5 

 mm. (fig. 13). (Young silver mullet have 2 spines 

 and 10 soft rays, rarely II, 9: the third spine 

 develops from the first ray which starts as a seg- 

 mented ray and fuses into a spine when the fish is 



