LINKAGE STUDIES IN MYTILUS-EDULIS, THE MUSSEL

Electrophoretic data at 10 allozyme loci from the offspring of six single pair matings of Mytilus edulis were analysed for linkage. Significant deviations from expected octopine dehydrogenase (Odh)/phosphoglycerate kinase (Pgk) and leucine aminopeptidase (Lap)/esterase D (EsD) di-locus genotype frequencies were evident in two families. In the former case, the recombination frequency was 0.463 suggesting epistasis but in the latter case a recombination frequency of 0.022 indicated almost complete linkage between the Lap and EsD loci. Other loci showing significant linkage were Odh/Lap and Odh/glucose phosphate isomerase (Gpi). Based on these data and other known linked loci in Mytilus a linkage group comprising Lap, EsD, Odh, mannose phosphate isomerase (Mpi) and possibly also Gpi is proposed. It is noted with interest that the closely related taxa M. edulis, M. galloprovincialis and M. trossulus are distinguished by significant allele frequency variations almost exclusively at loci in this linkage group.