Extraordinarily low evolutionary rates of short wavelength-sensitive opsin pseudogenes

Aquatic organisms such as cichlids, coelacanths, seals, and cetaceans are active in UV-blue color environments, but many of them mysteriously lost their abilities to detect these colors. The loss of these functions is a consequence of the pseudogenization of their short wavelength-sensitive (SWS1) opsin genes without gene duplication. We show that the SWS1 gene (BdenS1ψ) of the deep-sea fish, pearleye (Benthalbella dentata), became a pseudogene in a similar fashion about 130 million years ago (Mya) yet it is still transcribed. The rates of nucleotide substitution (~1.4 × 10(-9)/site/year) of the pseudogenes of these aquatic species as well as some prosimian and bat species are much smaller than the previous estimates for the globin and immunoglobulin pseudogenes.