Spectral sensitivity of the two-spotted goby Gobiusculus flavescens (Fabricius):: a physiological and behavioural study

Microspectrophotometry of Gobiusculus flavescens photoreceptors revealed a single rod visual pigment (gimel max at 508 nm) and the three cone pigments (gimel max 456, 531 and 553 nm). The cone population was dominated by identical double cones containing the middle-wave-sensitive (MWS) pigment, but with a small number of non-identical MWS/LWS (long-wave-sensitive) and identical LWS double cones. Small populations of large single cones also contained either the MWS or LWS pigment. The short-wave-sensitive (SWS) pigment was found in small single cones. Lens transmission was great reduced below 410 nm. The spectral sensitivity of the behaviourally determined reaction distance (RD) to prey at a high irradiance level (0.5 mu mol m(-2) s(-1)) correlated with the maximum sensitivity of the MWS cones, both peaking around 530 nm. However, at a lower irradiance level (0.015 mu mol m(-2) s(-1)) such a correlation was not so apparent. The RD was greatly reduced, though still maintaining a peak around 530-550 nm, but with a relatively smaller reduction in RD at shorter wavelengths. Optomotor behaviour displayed a somewhat similar spectral sensitivity to the RD responses at the higher light intensity. However, the peak was at slightly longer wavelengths at 550 nm, suggesting a greater input from LWS cones to the optomotor response.