Distribution of visual pigments in the Teleostei — A comment

Two types of visual pigments have been identified in the retinal rods of vertebrates — rhodopsin (A₁) and porphyropsin (A₂). Wald (1960) suggested a specific pattern of distribution for these pigments in vertebrates on the basis of their habitat salinity. However, data published in recent years on visual pigments have raised doubts as to the validity of Wald's hypothesis, especially with reference to teleost fishes. Hence the available data, old as well as new, have been reanalysed and it is suggested that the distribution of visual pigments in teleost fishes is correlated with their phylogeny, rather than with their habitat salinity per se.