Seasonal variation in cone sensitivity and short-wave absorbing visual pigments in the rudd Scardinius erythrophthalmus

Abstract

Microspectrophotometric and electroretinographic investigation of photoreceptor spectral sensitivity in the rudd Scardinius erythrophthalmus has revealed four spectral classes of cone with peak sensitivity in the ultra-violet, violet, green and red regions of the spectrum. These peak sensitivities were found to vary seasonally, and in response to artificial illumination, as a result of a change in the ratio of A1 to A2-based visual pigment in the cells. Short daylengths favoured the A2 pigment whereas long daylengths favoured the A1 analogue. Both the ultra-violet and violet-sensitive pigments have not previously been reported for the rudd. Evidence is presented supporting the hypothesis that the ultra-violet class of cells is not present in older fish.