FISHERY BULLETIN; VOL. 77, NO, 1 



Flexion larvae undergo little change in pigment 

 pattern from earlier stages. The triangular 

 patches of finfold pigment are diminished in size 

 and pigment intensity, but are visible by careful 

 examination in specimens through notochord flex- 

 ion. 



Following the completion of notochord flexion, 

 pigment on the tail spreads posteriad leaving only 

 the caudal peduncle unpigmented (Figure 9D). 

 The outlying regions of the head and body, par- 

 ticularly the pterygiophore region, are sparsely 

 pigmented compared with late larvae of other 

 Pleuronichthys species and H. guttulata. 



Transformed specimens develop heavy pigment 

 over the body giving them a mottled appearance. 

 Dark blotches appear along bases of the dorsal and 

 anal fins (Figure 10). 



Morphology. — Larvae of P. verticalts attain a size 

 intermediate between the large species. P. decur- 

 rens and P. coenosus, and the smaller P. ritteri. A 

 specimen with most of its yolk sac remaining is 2.4 

 mm NL (Table 9). The left eye is beginning to 

 migrate in a specimen as small as 7.3 mm SL and 

 transformation is almost complete at 9.2 mm SL. 

 The smallest available juvenile is 12.2 mm SL, 

 reared from eggs collected off San Diego, Calif 



Gut development follows the course of other 

 Pleuronichthys. Snout-anus length is about 50'~^ of 

 body length in preflexion and flexion stages and 



then is reduced in postflexion and early juvenile 

 stages. The gut begins to coil at about 4.0 mm NL 

 but the free terminal section does not become ver- 

 tical until at least 5.0 mm NL. 



As in the other species, relative head length 

 increases throughout the larval period and then 

 decreases at transformation. Snout length and eye 

 size undergo a gradual relative diminution during 

 the larval stages; however, relative eye width in- 

 creases sharply at transformation (Table 5). 



Larvae of P. verticalts are intermediate in body 

 depth when compared with other species of 

 Pleuronichthys (Table 5l. 



Fin and structural development. — P. veriicalis is 

 the only species for which we could clear and stain 

 a series of larvae (Tables 10, 11). The sequence of 

 fin formation was followed more precisely in this 

 species as was the sequence of ossification of other 

 structures including the vertebral column, sup- 

 porting bones of the caudal fin, branchiostegal 

 rays, gill rakers, and teeth. 



The caudal fin begins to form on the under side 

 of the body a short distance anterior to the tip of 

 the notochord on specimens of about 5.0 mm NL. 

 Some caudal rays form before flexion begins (Fig- 

 ure 11 A). Rays initially form at midcaudal and 

 those that will be associated with superior hypural 

 bones differentiate posteriorward, while those 

 that will be associated with inferior hypural bones 



Ficl'KE 10. — Reared transfonning specimen o( Plfurnnu-hthys uerticcilis, 11.0 mm. 



122 



