LINKAGE STUDIES IN MYTILUS-EDULIS, THE MUSSEL

Electrophoretic data at 10 allozyme loci from the offspring of six sin gle pair matings of Mytilus edulis were analysed for linkage. Signific ant deviations from expected octopine dehydrogenase (Odh)/phosphoglyce rate kinase (Pgk) and leucine aminopeptidase (Lap)/esterase D (EsD) di -locus genotype frequencies were evident in two families. In the forme r case, the recombination frequency was 0.463 suggesting epistasis but in the latter case a recombination frequency of 0.022 indicated almos t complete linkage between the Lap and EsD loci. Other loci showing si gnificant linkage were Odh/Lap and Odh/glucose phosphate isomerase (Gp i). Based on these data and other known linked loci in Mytilus a linka ge group comprising Lap, EsD, Odh, mannose phosphate isomerase (Mpi) a nd possibly also Gpi is proposed. It is noted with interest that the c losely related taxa M. edulis, M. galloprovincialis and M. trossulus a re distinguished by significant allele frequency variations almost exc lusively at loci in this linkage group.