THE ECOLOGY OF THE VISUAL PIGMENTS OF SNAPPERS (LUTJANIDAE) ON THE GREAT-BARRIER-REEF

The visual pigments in the retinal photoreceptors of 12 species of sna ppers of the genus Lutjanus (Teleostei; Perciformes; Lutjanidae) were measured by microspectrophotometry. All the species were caught on the Great Barrier Reef (Australia) but differ in the colour of the water in which they live. Some live in the clear blue water of the outer ree f, some in the greener water of the middle and inshore reefs and some in the more heavily stained mangrove and estuarine water. All the spec ies had double cones, each member of the pair containing a different v isual pigment. Using Baker's and Smith's (1982) model to predict the s pectral distribution of ambient light from chlorophyll and dissolved o rganic matter it was found that the absorption spectra of the visual p igments in the double cones were close to those that confer the maximu m sensitivity in the different water types. Single cones contained a b lue or violet-sensitive visual pigment. The visual pigments in the rod s showed little variation, their wavelength of maximum absorption alwa ys being in the region 489-502 nm.