LAROCHE: DEVELOPMENT OF LARVAL SMOOTH FLOUNDER 



5.8 mm 



6.4 mm 



7.4 mm 



Figure 7. — Flexion larvae of Pseudopleuronectes americanus. 



Several additional melanophores appear at this 

 location by 6.3 mm and appear on the caudal fin 

 near the base of the caudal fin rays after they form. 

 As the pterygiophores associated with the anal fin 

 rays begin to develop, between 6.3 and 6.4 mm, 

 melanophores separate from the postanal ventral 

 midline rows and appear as an irregular row along 

 the distal margins of the pterygiophores and along 

 the bases of the dorsal and anal rays by 6.6 mm. A 

 broken band of melanophores develops in the 

 proximal one-third of the dorsal and anal fins by 

 7.6 mm. 



Scattered metallic yellow chromatophores were 

 present over the head and body of newly hatched 

 larvae. These chromatophores disappear soon 

 after preservation in Formalin. No additional ob- 

 servations of chromatophore patterns were possi- 

 ble on larger field-collected larvae. 



Pseudopleuronectes americanus 



The eyes of P americanus lack pigmentation at 

 hatching ( =2.4 mm). Pigmentation begins to ap- 

 pear in the eyes of P americanus at =2.9 mm, and 

 the eyes are completely pigmented by 3.5 mm. 

 Expanded external melanophores are scattered 

 over the head of the smallest larva (2.4 mm). These 

 melanophores are faint and may be difficult to see. 

 Melanophores over the dorsolateral surfaces of the 

 head disappear by =3.5 mm. A few melanophores 

 remain on the upper and lower jaws and along the 

 ventral midline of the head (gular and isthmus 

 regions). No evidence of melanophore migration 

 was observed in P. americanus. One to several 

 internal melanophores are present along the an- 

 terior edge of the cleithrum often appearing under 

 the operculum on larvae >2.6 mm. One or two 



905 



