Spectral Sensitivity and Diversity of Visual Pigments in Cottoid Fishes

The photoreceptors and visual pigments of several coastal cottoid fish species (Cottoidea) from the Sea of Japan have been studied by microspectrophotometry and chromatography (HPLC). In the silverspotted sculpin Blepsias cirrhosus (Pallas, 1814) and the tentacled sculpin Porocottus allisi (Jordan & Starks, 1904), cones have increased long-wavelength sensitivity, with spectral sensitivity maxima up to 600–625 nm. Such a property is provided by a porphyropsin/rhodopsin mixture in photoreceptors and is combined with the yellow-orange corneal filters having changeable coloration. Some species exhibit individual differences in the composition of the visual pigment mixture. An assumption is made that the properties of the visual pigments and the light-protective eye media in sculpins and closely related species are an adaptation to shallow-water habitats (including the littoral zone) with bright light conditions during daytime.