FISHERY BULLETIN: VOL. 82, NO. 1 



This pattern persists until the larvae are about 2.5 

 mm long with a gradual increase in the number of 

 melanophores along the ventral margin of the tail. 

 The melanophores on the yolk sac and oil globule dis- 

 appear with the exception of one or two on the mid- 

 ventral line of the anterior part of the yolk sac. 



In larvae 4.0-5.0 mm long, most of the pigment is on 

 the peritoneum dorsal to the viscera and along the 

 midventral line. Anteriorly there is a melanophore at 

 the cleithral symphysis and posterior to it a large one 

 midventrally on the anterior belly and a smaller one 

 on the posterior belly. There is a prominent 

 melanophore on the hindgut just anterior to the anus. 

 Posterior to this there is a melanophore on most of 

 the anal pterygiophores; this pattern is continued 

 externally on the ventral myosepta. Dorsally there 

 are several melanophores on the posterior 

 pterygiophores of the dorsal fin. There are usually a 

 few scattered spots on the finfold and, on some 

 specimens, a few on the sides. 



The peritoneal pigment becomes denser and more 

 prominent in 9-10 mm larvae, however, it is often 

 obscured because of the opacity of the thickening 

 body musculature in preserved specimens. The 

 hindgut is nearly covered by large melanophores. 

 The melanophores on the midventral line are still 

 present, usually accompanied by two or three smaller 

 ones. The melanophore just posterior to the anus is 

 still present, but less prominent. 



The trunk and tail pigment is more extensive at 9- 1 

 mm. There are many more pigment spots along the 

 sides, but these are still widely spaced, especially 

 anteriorly. There is pigment along the bases of the 

 dorsal and anal fins that continues posterior to them 

 to the procurrent caudal rays. A line of melanophores 

 runs dorsoventrally at about the juncture of the 

 caudal fin rays and caudal bones. Internally there are 

 melanophores near the bases of the haemal and 

 neural arches. These become increasingly obscure as 

 the body musculature thickens. 



Pigment development beyond this size is charac- 

 terized by the development of the barred pattern of 

 the juvenile accompanied by a general increase in 

 pigment everywhere, especially above the mid- 

 lateral line. 



OSSIFICATION 



A total of 17 fish were stained with Alizarin Red to 

 determine where ossification began and the 

 sequence in which the bones ossified. A summary of 

 osteological development is presented in Table 3. 



There is no dye uptake in 5.2 or 6.0 mm larvae, 

 although the cartilaginous skeleton is easily dis- 



tinguished. Cartilaginous hypural plates are present 

 in larvae undergoing notochord flexure (5.4-5.6 mm). 

 The first ossification occurs in skulls of 6.1 mm lar- 

 vae. The premaxillary, maxillary, dentary, articular, 

 and quadrate bones associated with the jaws, the pre- 

 operculum, hyomandibular, branchiostegal rays, and 

 cleithrum showed varying degrees of dye uptake. 

 There is no ossification posterior to the cleithrum. 



By 7.0 mm more ossification of the skull occurs, 

 notably the pterygoid, metapterygoid, opercular 

 series, supracleithrum, and frontal bones. The cir- 

 cumorbitals, as well as the parasphenoid and the 

 scapula, show the beginning of dye uptake. Ossifica- 

 tion has begun in the first 10 vertebrae, the neural 

 spines of the first 4 vertebrae, and the pectoral and 

 caudal fin rays. 



In 9.3 mm specimens the skull is further developed; 

 teeth are visible and the lachrymal, dermethmoid, 

 nasal, prefrontal, and urohyal bones show varying 

 degrees of ossification. The postcleithrum is well 

 developed and the radials, scapula, and coracoid are 

 ossifying. The entire vertebral column is ossified with 

 the exception of the ultral centrum and penultimate 

 vertebrae. Both haemal and neural spines are 

 ossified. The pleural ribs, and the dorsal and anal fin 

 rays are beginning to ossify; hypural plates and 

 caudal fin rays are partially ossified. 



By 10.8 mm the distal vertebrae (caudal complex) 

 have ossified and scales are present. The pelvic fin 

 supports and rays show some dye uptake. Pterygio- 

 phores are present as cartilage. All the dorsal and 

 anal fin rays and spines have ossified. 



Skull development and ossification of most of the 

 bones of the skull is complete by 14.5 mm. The 

 radials and scapula which were just beginning to 

 ossify in the 10.8 mm fish are now complete. Pelvic 

 fin supports are complete. The pleural ribs are 



TABLE 3. — Summary of osteological development in laboratory 

 reared larvae of Stenotomus chryxops. 



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