POWELL and GORDY: EGG AND LARVAL DEVELOPMENT OF THE SPOT 



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A. Body depth 



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STANDARD LENGTH (mm) 



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Figure 3. — Body proportions of Leiostomus xanthurus relative to the standard length: A, body depth; B, preanus length and head 



length. 



Fin Development (Table 1) 



Rayed fins initiated development in the follow- 

 ing sequence: caudal, anal, second dorsal, first 

 dorsal and pectoral, and pelvic. The adult com- 

 plement of spines and rays was attained in the 

 following sequence: principal caudal rays (9 upper 

 + 8 lower), anal (II, 12-13), second dorsal (I, 29-35), 

 first dorsal (IX-XI) and pelvic (1,5), secondary 

 caudal rays (6-8 upper and lower), and pectoral 

 (20-22). 



A thickened area of tissue on the ventral side of 

 the notochord was the first indication of caudal fin 

 development (Figure 6). The rays began to form at 

 the middle of the fin and developed dorsally and 

 ventrally simultaneously. Principal caudal rays 

 developed rapidly. They were first visible at 4.6 

 mm SL and by 65.3 mm SL the adult complement 

 (9 upper -t- 8 lower), which is shared by all sci- 



aenids, was reached. On the other hand, secondary 

 caudal rays were slow to form. All specimens 

 5=14.4 mm SL had a complete caudal fin. 



Dorsal fin rays started to form near the middle 

 of the fin, between the 8th and 17th vertebrae, then 

 developed anteriorly and posteriorly simultane- 

 ously. Soft rays were first observed at 6.7 mm SL. A 

 full complement of second dorsal fin spines and 

 soft rays was attained at 8.8 mm SL. A full com- 

 plement of first dorsal fin spines was attained at 

 9.0 mm SL, and although the second dorsal on that 

 particular larvae had a ray count within the adult 

 range, the last soft ray was not formed. All speci- 

 mens ^10.8 mm SL had a complete dorsal fin. All 

 our specimens had a first dorsal fin of 10 spines. 



Anal fin rays started to form near the middle of 

 the fin, between the 11th and 15th vertebrae, and 

 then developed rapidly anteriorly and posteriorly. 

 Soft rays were first observed at 6.3 mm SL and 



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