POWELL and GORDY: EGG AND LARVAL DEVELOPMENT OF THE SPOT 



4.6 mm SL 



B 



5.1 mm SL 



Figure lO. — Parts of axial skeleton used in counting: (A) total vertebrae (only myosepta useful in counting vertebrae are shown) and 

 (B) precaudal and caudal vertebrae in Leiostomus xanthurus early larvae. Ns, neural spine; Hs, haemal spine; My3, myosepta 

 associated with the third neural spine; Ph, parhypural; Hy, hypural bone; Eps, epurals; Nc, notochord. 



fewer dorsal melanophores and more ventral 

 melanophores. Finally, at the late yolk-sac stage 

 (Figure 6A) a characteristic body pigment pattern 

 was established (i.e., a single row of melanophores 

 along the ventral midline) that persisted through- 

 out the larval period. 



Distinguishing characteristics of postyolk-sac 

 spot larvae have been reported (Fruge and Trues- 

 dale 1978; Powles and Stender 1978), but the size 

 or stage when spot larvae acquire these charac- 

 teristics has generally been unknown. After yolk- 

 sac absorption, there were five characteristic pig- 



mented areas that developed in the region of the 

 head and abdomen (Figure 6B-E) 



1. Embedded melanophores over the air bladder 

 and hindgut. They were observed on the 

 youngest preflexion larvae (2.3 mm SL). 



2. A triangle on the ventral side of the abdomen 

 composed of a well-defined melanophore just 

 anterior to the anus and a faint melanophore at 

 each future pelvic fin base, although one was 

 lacking at times (see Lippson and Moran 1974 

 for illustration), This pattern was occasionally 



711 



