Over Vertigo moulinsiana (Dupuy) en haar voorkomen in Nederland

The authors give a survey of what is known of the distribution of Vertigo moulinsiana in Europe. The only localities known in the Netherlands are situated in the valley of the river Geleen, province of Limburg, where this snail was discovered by the second author in 1943. There are four localities in two municipalities: Schinnen and Nuth. Visiting three of these localities on October 4th, 1957, the first author found Vertigo moulinsiana again at a site South of Heisterbrug in a vegetation consisting of elements of the plant communities Magnocaricion elatae (Koch) and Valerianeto-Filipenduletum (Sissingh) in the company of Trichia hispida (L), Columella edentula (Drap.), Vitrea crystallina (Müll.), Vitrea contracta Wstld, Vitrina pellucida (Müll.), Eucobresia diaphana (Drap.), Succinea putris (L.), Deroceras reticulatum (Müll.), D. laeve (Müll.), Eulota fruticum (Müll.), and Zenobiella incarnata (Müll.). A site between Schinnen and Thull was found to have a vegetation belonging to the Alnetum cardaminetosum amarae (Meyer Drees) bordered by a Juncetum acutiflori (Br.-Bl.) in which Succinea putris (L.), Arion spp., Eucobresia diaphana (Drap.), Zenobiella incarnata (Müll.), Goniodiscus rotundatus (Müll.), and Retinella hammonis (Strom) were living. The third site South of Kathagen, a wilderness of Urtica dioica mixed with Carex and Phragmites, prooved not to be the exact locality given by the second author. V. moulinsiana was not found there. The mollusc fauna consisted of Eulota fruticum (Müll.), Zenobiella incarnata (Müll.), Succinea putris (L-), Goniodiscus rotundatus (Müll.), Trichia hispida (L.), Columella edentula (Drap.), Carychium tridentatum (Risso), Acanthinula aculeata (Müll.), Vitrina pellucida (Müll), Oxychilus cellarius (Müller), and Retinella nitidula (Drap.). Many of the specimens of V. moulinsiana were juveniles. V. moulinsiana is a very rare animal in Europe. It is presumably a relict from the Atlanticum. During that period of the Holocene it had its greatest distribution in Europe. Having studied the literature on V. moulinsiana the authors feel that the now common opinion is right in accepting V. moulinsiana as a mediterranean element in the European fauna. It seems all right to accept changes in climate since the Atlanticum as responsible agents for the regression of this mollusc towards the South. This, however, does not mean that this movement is still going on. The animals maintain themselves in the North under locally favourable conditions. That these conditions gradually disappear is a result of men’s interfering by reclaiming marshes in which V. moulinsiana still lives. It remains to be seen what these conditions exactly are. Atmospheric humidity and temperature are important factors. Studies on the microclimate in relation with this mollusc have never been made as far as we know. So far V. moulinsiana is bound to Carex spp. and other marsh plants where it can feed upon fungi parasitizing on Carex and Glyceria. In the Netherlands the snail is not bound to lime marshes. The localities in this country have an eutrophic character and are decidedly not poor in lime as they are situated in rich löss soils. Typical lime marshes are to the best of our knowledge calcareous and poor in other nutrients. In this respect the German localities in Holocene and Pleistocene “Quellkalken und Moormergeln” (SCHMIERER, 1936, p. 8) seem different. PHILLIPS (1908) mentioned that in Ireland V. moulinsiana hibernates together with Succinea putris in the forks of Alnus branches among dead leaves. Others saw them at the underside of dead and dry Glyceria and Carex leaves which are, allthough bent, still standing in winter. About propagation we know only that young snails appear in the populations in October. PHILLIPS (1908) concluded that V. moulinsiana is “apparently viviparous” as he saw the adult snails “bearing young ones on the back of their shells”.