Convergent evolution of the red- and green-like visual pigment genes in fish, Astyanax fasciatus, and human.

We have isolated and sequenced genes from the blind cave fish, Astyanax fasciatus, that are homologous to the human red and green visual pigment genes. The data strongly suggest that, like human, these fish have one red-like visual pigment gene and multiple green-like visual pigment genes. By comparing the DNA sequences of the human and fish visual pigment genes and knowing their phylogenetic relationship, one can infer the direction of amino acid substitutions in the red and green visual pigments. The results indicate that the red pigments in human and fish evolved from the green pigment independently by identical amino acid substitutions in only a few key positions.