Critical amino acid replacements in the rhodopsin gene of 19 teleost species occupying different light environments from shallow-waters to the deep-sea

Critical amino acid replacements in opsin proteins shift the maximal absorbance of visual pigments to perceive different photic environments (spectral tuning). Here we studied the molecular basis for spectral tuning of the rhodopsin (RH1) pigment in 19 species of marine teleosts inhabiting different light environments, from shallow waters to the deep-sea. We identified replacements at the critical sites 194, 195, 292 and 299, which have been defined relative to the bovine RH1 gene and are known to be involved in shifting the λmax value of RH1 pigments towards the blue light. All the species had the substitutions P194R and H195A. However, we detected a relationship between the combination of amino acids at the critical sites 292 and 299 and the maximum depth of the species under study. The combination 292S/299A was only found in the deep-sea congeners Hoplostethus atlanticus and H. mediterraneus. This may reflects an adaptation of these species to the bathypelagic light environment. All the epipelagic species studied and the epi-mesopelgic species Parapercis colias, had the combination 292A/299S, except Chelidonichthys kumu (292A/299A) and Notolabrus celidotus (292S/299S). It is possible that the combination 292A/299S is an adaptation to longer wavelengths of light in comparison with the deeper species. This is the first study in the rhodopsin gene sequence in all the species under study, except for Macruronus novaezelandiae and H. mediterraneus.