The spectral sensitivity of the retinal photoreceptors of the Asiatic smelt Osmerus dentex (Steindachner et Kner, 1870)

The spectral sensitivity and complement of the retinal photoreceptors of the Asiatic smelt from the Sea of Japan were studied by microspectrophotometry and light microscopy. Apart from rods, one type of single cones and one type of unequal double cones were found in major parts of the retina. The dominant type of the cone pattern (mosaic) is a row pattern consisting of various linear arrangements of separate single and double cones. The absorbance maxima of rods and a majority of singe cones and double cones equaled 516, 425 and 514/565 nm, respectively. It has been established that all of the pigments are based on retinal. The findings are compared with data on the osmerid retina from the literature and discussed with respect to the adaptations to light conditions, peculiarities of behavior, and seasonal migrations of smelts.