MITOCHONDRIAL-DNA HETEROPLASMY IN EUROPEAN POPULATIONS OF THE MUSSEL MYTILUS-TROSSULUS

Mitochondrial DNA (mtDNA) of Mytilus trossulus from the Gulf of Gdansk (southern Baltic) and M. edulis from Swansea Bay, South Wales, UK, co llected in 1991, was studied by restriction-enzyme analysis. These two species were more similar to each other in haplotype frequencies than either was to M. gallo-provincialis from Britain, M. trossulus resemb les M. edulis in having a high frequency of heteroplasmy restricted to males. However, in contrast to M. edulis where restriction-site heter oplasmy predominates, in M. trossulus heteroplasmic individuals posses s two genomes which differ in length by up to 3 kilobases.