De verspreiding van Ferrissia wautieri (Mirolli) (Gastropoda, Ancylidae) in Nederland

The distribution of Ferrissia wautieri in the Netherlands Ferrissia wautieri (Mirolli, 1960) (Gastropoda, Ancylidae) has been recorded up to now from 15 localities in the Netherlands, all situated in the freshwater areas of the country (fig. 1). The species occurs in eutrophic, stagnant or weakly flowing, mostly larger-sized waters (11 localities) and eutrophicated moorland pools (4 localities) on diverse substrates such as plants (8 localities) and stones (2 localities), but also on the bottom, especially in winter time. In two localities F. wautieri was recorded from the outlets of an electric power station, where it behaves as a thermophilous species as it occurred in very large numbers near the outlets where the water is warmed by the discharge of cooling water, while it was hardly found near the intakes. As the species is recorded as a fossil from Holocene deposits in the Netherlands it cannot be considered as a recent immigrant such as some other species of molluscs occurring near the outlets of power stations. The thermophilous character of F. wautieri is also shown by its distribution in Europe; it occurs in Mediterranean-Atlantic areas and is absent where winters are severe. So far only ancyloids have been found in the Netherlands and all records are from permanent waters.