Phenotypes of phosphoglucose isomerase in some bivalve molluscs

1. 1. Electrophoretic variants of phosphoglucose isomerase (E.C. 5.3.1.9) have been studied in six species of bivalve molluscs. 2. 2. Two phenotypes were observed in Ostrea edulis, three in Mytilus edulis, four in Crassostrea angulata, six in Ensis ensis, eleven in Tapes decussatus and twenty-five in Pecten maximus. 3. 3. The enzyme is inferred to be a dimer encoded at a single polymorphic locus in all species. There are two alleles at this locus in O. edulis and in M. edulis, four in C. angulata, three in E. ensis, five in T. decussatus and nine in P. maximus. 4. 4. The occurrence of enzyme polymorphisms in bivalve molluscs is discussed briefly.