Two morphotypes of the New Zealand mud snail Potamopyrgus antipodarum (J.E. Gray, 1843) (Mollusca: Hydrobiidae) invade Lithuanian lakes

Abstract

The New Zealand mud snail, Potamopyrgus antipodarum, was found in four lakes and one medium-sized river located in the southern part of Lithuania during 2010. These are the first records of P. antipodarum from Lithuanian freshwaters, a considerable distance from the Curonian Lagoon wherein the species was reported during the 1950s. Available information shows that the species has invaded quite recently. Two morphotypes of the species, the regular and carinatus (keeled) forms, were observed in three lakes. The presence of separate morphotypes and variation in shell morphometry suggest multiple (at least two) independent invasion events, and species expansion on a local scale. The most abundant population of the invasive snail was recorded in Lake Dusia which is an inland lake of exceptional importance for staging and moulting of migratory waterfowl. Thus, the most probable vector of the invasion and local dispersal is ornithochory, while translocation with fish stocking material may also be operating. Further rapid expansion of the species in Lithuanian lakes and rivers seems very possible.