A remarkable record of a very rare freshwater snail Borysthenia naticina (Menke, 1845) in North-East Germany compared with three Lithuanian records

Borysthenia naticina (Menke) is among the rarest and most threatened freshwater molluscs in Germany. Only in southern Germany, in the Bavarian part of the Danube River, previous studies clearly indicate a recent occurrence of this species. Some imprecise data were given for northern Germany from the Oder River; prehistoric records (Diluvium) also exist. However, all these "Oder River literature sources" are hard to locate and it was impossible to find any reliable recent records of B. naticina in the German parts of the Oder River. This study documents the occurrence of a recent population of this very rare Pontic-Baltic species in the lower course of the Oder River. Ecological information on the habitat and accompanying freshwater molluscs is given. The findings are compared with the data on the Lithuanian localities in the Nemunas River.