Visual pigments of cichlid fishes from Malawi

Abstract

Visual pigments were studied from 23 species of cichlid fishes from Lake Malawi, four species from the Lower Shire River, and one from Lake Chilwa. The water in Lake Malawi is very clear, and the fishes occupying it have visual pigments that vary with the depth at which they live, with the maximal absorption ranging from just above 500 nm for surface living forms to about 492 nm for species living at 50–90 fathoms. The visual pigment of the species from Lake Chilwa, which is highly turbid, absorbs maximally at approx 530 nm, while the visual pigments of the Lower Shire species are intermediate. The results are also compared to previous data for Amazonian cichlids. The visual pigments of the Amazonian species show much greater variation, both within and between species, than do those of Lake Malawi cichlids. It is suggested that the variation between the visual pigments of different fishes occupying a given habitat may be related to the variability of the light conditions in their environment.