Stand van zaken ten aanzien van de verspreiding van de Smurfslak Ferrissia clessiniana (Jickeli, 1882) in de Nederlandse binnenwateren

This article is a sequel to a paper by Gerrit Kroon from 1981 in which he reported the finding in October 1980 of Ferrissia wautieri on leaves of aquatic plants in a cold greenhouse in the Amstelpark in Amsterdam. Here all information currently available on the distribution of Ferrissia clessiniana (Jickeli, 1882) in the Netherlands is provided. In this paper it will be assumed that the name Ferrissia clessiniana (Jickeli, 1882) deserves priority over the name Ferrissia wautieri (Mirolli, 1960). Accumulated data from different sources indicate that Ferrissia clessiniana is not rare in Dutch freshwater (until 2011 it was found at 451 different locations). The most likely mode of distribution in the Dutch inland waters is through dispersion of aquatic plants. However, Ferrissia clessiniana (size: up to 3 mm) may be confused with juvenile specimens of Acroloxus lacustris (Linnaeus,1758) (size: 4-7 mm), even more so because both species live in the same biotope. Recovery of fossil specimens of Ferrissia clessiniana in the Netherlands demonstrates that this species is endemic to the Dutch fauna.