SUMIDA ET AL- EARLY DEVELOPMENT OF SEVEN FLATFISHES 

 129° 125° 121° 



40' 



35' 



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20° 



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T- 



1- 



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-r 



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V 



T" 



MENDOCINO 



MAGDflLENA _ 



40° 



35° 



30° 



25° 



115° 



110° 



106° 



Figure 18. — Distribution of eggs and larvae of Pleuronichthys 

 ritteri examined in this study. (Triangles represent eggs, open 

 circles larvae, and closed circles eggs and larvae. t 



At the initiation of dorsal and anal fin forma- 

 tion, the tail pigment spreads out dorsally and 

 ventrally onto the finfold, resulting in conspicuous 



dark mounds of pigment opposing each other in 

 the area between the body and the dorsal and anal 

 fin bases (Figure 19C). The tops of the head, nape, 

 and shoulder area are pigmented in contrast to P. 

 ritteri. which has an unpigmented streak dorsally 

 (Figure 19D). Flexion, postflexion, and early 

 transforming specimens maintain the earlier 

 pigment pattern and the only obvious change is a 

 slight posteriad extension of trunk pigment, leav- 

 ing 5 or 6 unpigmented myomeres posteriorly 

 compared with 9 or 10 in earlier stages (Figure 

 20). The base of the pectoral fin acquires more 

 pigment spots in postflexion larvae, and pigment 

 on the head similarly increases in density (Figure 

 20B). 



Preserved small juveniles are brownish-black 

 with numerous small, dark spots scattered over 

 the body and pterygiophores, giving them a mot- 

 tled appearance (Figure 21). 



Morphology. — Our smallest yolk-sac larva is 2.2 

 mm NL and has a posteriorly positioned oil 

 globule 0.14 mm in diameter (Figure 19A). The 

 left eye is beginning to migrate in a specimen 4.4 

 mm SL and is complete in a 7.3-mm SL larva 

 (Table 16). The smallest available juvenile was 

 11.2 mm SL. 



A major distinguishing feature of Hypf^opxetta 

 larvae is the presence of a pterotic spine on each 

 side of the head. The spines are present on the 

 smallest yolk-sac larva and are prominent in most 

 preflexion larvae. The spines begin to regress on 

 late preflexion larvae, and are totally regressed in 

 late flexion specimens. In P. deciirrens the spines 

 are well developed throughout the larval period 

 and begin to regress late in the postflexion stage. 



Although mean relative body depth of H. gut- 

 tiilata larvae increases with development, it is 

 slightly less in postflexion specimens than in any 

 species of Pleuronichthys , except P. ocellatiis (Ta- 

 ble 5). In newly transformed juveniles, however, 

 relative body depth is greater than in any species 

 oi Pleuronichthys. As a juvenile. H. guttulata as- 

 sumes a diamond-shaped body form. 



Relative body width is useful to separate Hyp- 

 sopsetta larvae from those of P. ritteri. As shown in 

 Figures 15D and 19D, larvae of Hypsopsetta have 

 narrower bodies. 



Fin formation. — The caudal fin forms on larvae 

 between 4.0 and 5.2 mm NL and is complete on 

 some specimens as small as 4.4 mm (Table 17). The 

 dorsal and anal fins form simultaneously with the 



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