Enzyme variation in marine and estuarine populations of the chitonSypharochiton pelliserpentis

Abstract

Enzyme variation in sheltered-and exposed-marine populations and an estuarine mudflat population of the chiton Sypharochiton pelliserpentis was examined by polyacrylamide gel electrophoresis. Six loci were analysed, of which Idh-l, Idh-2, and Me-l were monomorphic and Est-2, Mdh-l, and Me-2 were polymorphic. All populations shared the same alleles at all loci. A heterozygote deficiency was detected at the Est-2 locus for the exposed-marine population and a heterozygote excess was found at the Mdh-l locus for the sheltered-marine population where allele frequencies were associated with chiton age. Differences were found in allele frequencies between the sheltered-and exposed-marine populations at the Est-2 locus and between females of the marine and estuarine populations at Mdh-1 locus. The Idh-2 locus showed variation in enzyme activity which was neither age nor sex specific, but appeared to be associated with different habitats. Marine population subsamples from high-shore and low-shore levels showed no significant differences in allele frequencies.