Protein variation in the marine bivalve Scrobicularia plana

Seventeen enzyme loci have been assayed for electrophoretically detectable variation in a population of the marine bivalve Scrobicularia plana. Mean heterozygosity is 0.120 +/- 0.033. In a comparison involving thirteen enzymes there is a significant correlation between heterozygosity in S. plana and Mytilus edulis and a suggestion of lower mean heterozygosity in S. plana. These findings are discussed in relation to current theories concerning the selective significance of protein variation.