The ecology of cone pigments in teleost fishes

The visual pigments in the retinae of 18 species of fishes were measured microspectrophotometrically and assigned to specific cone types. The major ecological implications of these data are seen by grouping the fishes into habitat classes based on spectral quality of the water and depth. It is seen that double and twin cones in the examined species contain a visual pigment roughly matching the water background spacelight, while single cones occupying typically the “additional” position in a square mosaic unit are invariably blue-sensitive and offset from the water transmission maximum. In photopic dichromats the central single cone of a square unit was found to contain a pigment identical to that found in the twin cones. The relevance of these findings to contrast enhancement, adaptation to rapid changes in spectral quality of the water, and formation of “ghost” pigments through opponancy is also discussed.