Polymorphism of the rod visual pigment between allopatric populations of the sand goby (Pomatoschistus minutus) : a microspectrophotometric study

Absorbance spectra were measured by microspectrophotometry in retinal rods of sand gobies (Pomatoschistus minutus) from four allopatric populations (Baltic Sea, Swedish west coast, English Channel and Adriatic Sea). Mean (± S.E.M.) wavelengths of maximum absorbance (max) were 508.3±0.5 nm, 505.4±0.2 nm, 506.2±0.3 nm and 503.0±0.3 nm, respectively. Pairwise comparison between the populations (post-ANOVA Scheffe's test) shows that each of the max differences, except that between the Swedish west coast and the English Channel, is statistically significant (P