Changes in Scotopic Spectral Sensitivity of Ayu Plecoglossus altivelis

Abstract

The composition of visual pigment of ayu caught in the sea, a river and lake Biwa was investigated. Ayu has two kinds of visual pigment, rhodopsin and porphyropsin, with estimated λmax of 503 nm and 528 or 529 nm, respectively. It was found that rhodopsin dominated in the retina during their sea lives, while conversely porphyropsin was dominant in the retina during their freshwater lives. In the landlocked ayu, rhodopsin was dominant throghout the year. It is suggested that the spectral sensitivity of amphidromous ayu changes between λmax of rhodopsin and λmax of porphyropsin, whereas that of landlocked ayu tends toward the short wavelength side of λmax all the year round.