• Journal of Aquaculture
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• v.11 no.3
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• pp.295-301
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• 1998

Since the end of the Pliocene, ancestral strains of Astyanax fasciatus have been accidently washed into different caves at the time of flooding and have lost their eyes and body pigments. Availability of this independently derived cave fish and their ancestral form within a single species provided a unique opportunity for studying the process of molecular evolution of the visual pigment gene. The nucleotide sequence comparisons of an ancestral river fish and two cave fish showed that nucleotide polymorphism of a green-like visual pigment gene between the eyed and blind form of A. fasciatus was much higher than that between the same blind form. Considering the number of nucleotide substitutions per nucleotide site and the direction of the nucleotide substitutions, more nucleotide substituions between the different forms of fish rater than the same one were probably due to more frequent mutations in the eyed river form. Nucleotide substitutions per site at the intron have been ocurred more than three times faster than those at the exon. This result indicates that the functional constraint has affected the green-like visual pigment gene of the blind cave fish although its eye sight is no longer required.