Molecular cloning of cDNA encoding red opsin gene in the retinas of five Antarctic notothenioid fishes

Previous evidence suggested that notothenioid fish had lost red-sensitive (LWS) visual pigment and photoreceptors, but retained ultraviolet-sensitive (SWS1), blue-sensitive (SWS2), and green-sensitive (RH2) pigments. We used RT-PCR and Southern blot to isolate the LWS opsin gene in five notothenioid species. We determined full-coding LWS opsin sequences and genomic sequences. The expected peak absorbance of the LWS opsin, based on the five-sites rule that is primarily responsible for the spectral sensitivities in vertebrates, ranged from 541 to 553 nm. In Antarctic waters, light of this wavelength penetrates to dozens of meters. Thus, we conclude that notothenioids use tetrachromatic color vision in shallower waters, at least during the Antarctic summer.