The visual pigments of freshwater fishes

Abstract

Dark-adapted retinae from 59 species of freshwater fishes were extracted in digitonin and analyzed for visual pigment content using the method of partial bleaching. Results of this survey, combined with the investigations of others, show that the classic view of visual pigment distribution among vertebrates is erroneous. Visual pigments based on both retinene 1 and retinene 2 occur commonly among freshwater fishes, even in groups that are neither euryhaline nor migratory. Evidence suggests that the distribution of these visual pigments is probably correlated to photic environment.