Effect of Season and Sex on the Photopic Spectral Sensitivity of the Three-Spined Stickleback

Abstract

1. The photopic spectral sensitivity of the three-spined stickleback Gasterosteus aculeatus was obtained behaviourally using the optomotor response as the index of sensitivity. Our experiments were designed to determine whether spectral sensitivity was affected (i) by the sex of the fish, and (ii) by season. 2. In females γmax occurred at approximately 510 run. and 594 nm. In males the corresponding values were 502 nm. and 594 nm. Thus there appears to be a small but consistent difference of the order of 10 nm. between the shorter wavelength peaks of males and females. 3. In males the spectral sensitivity appears to remain virtually unchanged throughout the year. By contrast, during the summer months when reproductive activity is highest, the optomotor threshold for females at the red (594 nm.) end of the spectrum is considerably lower than the corresponding threshold value for males. This difference between the sexes disappears during winter months when reproductive activity is at a minimum.