Ferrissia wautieri (Gastropoda, Basommatophora), nieuw voor Nederland

Ferrissia wautieri in the Netherlands Ferrissia wautieri (Mirolli, 1960) has been recorded for the First time in the Netherlands. A population of this species was found to occur in the northern part of the “Roelofsven-Zuid”, one of the “Hatertse- and Overasseltse vennen” (moorland pools, situated southwest of Nijmegen, Province of Gelderland). This moorland pool is now surrounded by grassland and is metatrophic due to eutrophication. The snails, all ancyloids, have been found on Typha, Menyanthes, Rorippa, Utricularia, and Hypericum. By squashing some specimens, it was found that they eat periphyton, especially Chlorophyceae and diatoms. Some data of the Roelofsven-Zuid and other investigated metatrophic waters in the neighbourhood are recorded in table 1. One specimen has been collected by Mrs. A. van Gessel in another eutrophicated moorland pool, the “Beuven” (Province of Noord-Brabant), on 15th October 1977, together with other molluscs mentioned in the text. Some data of this water are recorded in table 2. The local vegetation consists of Littorella, Eleocharis, Elatine, and Cladium. In addition many specimens have been found in the collection of the Zoological Museum, Amsterdam, which were collected by L. Renders and M.C. de Wilde-Stuurman during an investigation of the molluscan fauna of the eutrophic Abcoudermeer and connected waters. The chlorinity fluctuated here from 120- 580 mg/l. Most specimens were collected in the reed beds. The specimens had been classified with Ancylus fluviatilis and partly with Acroloxus lacustris. All specimens of Ferrissia wautieri collected in the Netherlands were of the ancyloid type.