Brackish-water Plathelminthes from the Faroe Islands

Species-rich communities of brackish-water plathelminths of the European continental coast and of the north American Atlantic coast are known to be most similar. In contrast nothing has been recorded about a possible settlement of corresponding faunal elements between the continents on volcanic islands which were covered by glaciers in the Pleistocene. At the Faroe Islands 2 freshwater species, 11 marine-euryhaline species and 12 genuine brackish-water organisms were found in minute brackish-water biotopes with highly variable salinity. Macrostomum curvituba Luther, Minona baltica Karling & Kinnader and Coronhelmis lutheri Ax are the most abundant species. Several brackish-water plathelminths are able to tolerate freshwater conditions. Most probably they have evolved mechanisms which are comparable to those of limnetic organisms allowing long distance transport across the sea in an inactive state.