Genetic traits in the bivalve Mytilus from Europe, with an emphasis on Arctic populations

Genetic and some ecophysiological traits of mussels collected in the Europe an Arctic, up to their northeastern distribution limit in the Barents Sea, were studied and compared with traits of mussels from the Mediterranean, At lantic and Baltic. The genetic traits of these populations we-re analysed b y isoenzyme electrophoresis on seven loci in order to assess the Mytilus co mplex to which populations in the Arctic region belong. Ecophysiological va riables, the weight-index and glycogen were analysed to assess the physiolo gical fitness of the populations. Three distinct groups were recognised: (1 ) Mytilus (edulis) galloprovincialis in the Mediterranean and Spain, (2) M. (edulis) edulis along the Atlantic coast from the Netherlands northwards i nto Russia, and (3) the Baltic Mytilus (edulis) trossulus. The mussels from populations in the Russian Arctic all belong to the Atlantic Mytilus (edul is) edulis group. The genetic variability and ecophysiological measures ind icated that the sub-Arctic White Sea mussel populations have a relatively l ower performance capacity, whereas those in the Arctic at the edge of their northern distribution showed a surprisingly strong performance.