Retinoic acid stimulates development of adult-type chromatophores in the flounder.

Premetamorphic flounder larvae were administered different doses of 9-cis retinoic acid (9cRA). 9cRA at 25 nM (the highest dose) not only stimulated adult-type (ad-) chromatophore development on the ocular (eyed) side, but also induced the development of ad-chromatophores on the blind (non-eyed) side of the metamorphosed fish. The ad-chromatophore development was stimulated by 9cRA only when administered to the larvae that were at late premetamorphosis and at early prometamorphosis. Ad-chromatophores actually appear much later, at the end of metamorphosis. 9cRA was not effective at later stages of metamorphosis. These results suggest that 9cRA stimulated the development or determination of the developmental fate of neural crest cells for chromatophores. The present results also suggest the presence of immature chromatophores or neural crest cells on both sides of the larval body of the flounder and that the ad-chromatophore development is somehow inhibited on the blind side in spontaneous metamorphosis. All-trans retinoic acid (atRA) had a similar effect on the ad-chromatophore development. In addition, both types of RAs affected the development of fin rays of the fish, resulting in deformity of fins when administered at high doses early in metamorphosis. The teratogenic effect of atRA was greater than that of 9cRA. Copyright 1999 Wiley-Liss, Inc.