The descriptive text, below the map, is from the Cornish Red Data Book (2009). The map on this web page depicts the organisms distribution and shows the records made pre-2000 and those made since.
Range & Status
Syn. Lymnaea glabra (O.F. Muller). Occurs only in north-west Europe, reaching about 61\'baN. latitude in Scandinavia. In Britain the species has scattered locations, mainly in the south-west and northern counties. There have been many population extinctions, especially in the central lowland counties of England.
Between 1965 and 1999 O. glabra was recorded in nine tetrads, four from VC1 and five from VC2. Re-examination of available voucher specimens shows that some records from sand-dune pool habitats in VC1 were misidentification of other species of Lymnaeidae. Recording of the species since 1999 has included surveys at Tregoss (Goss Moor NNR) and Red Moor NR between 2002 and 2004 funded by English Nature (now Natural England). Data mainly from these surveys showed the species was present in nine tetrads in VC2. Thus, it occurred widely at Tregoss (SW69U, SW94K, SW95P, SW96K, SW96Q), at Red Moor (SX06R), at Retire Common (SX06B), at Warleggan River (SX17L) and at Bowithick (SX18W). There are no post-1999 records from VC1, where its current status is uncertain.
Habitat & Ecology
O. glabra typically lives in water low in nutrients in ponds and ditches, especially places which dry out periodically. In temporary habitats the species may ' disappear' , and hence be overlooked during dry periods, becoming more conspicuous as it matures during periods of flooding. At Goss Moor the species is found in several deep permanent ponds which seem to allow a more stable seasonal life-cycle as it is not dependant on seasonal flooding. Immatures (with shells less than 6 mm in height) cannot be reliably distinguished from immatures of Stagnicola fuscus (C. Pfeiffer) with which it frequently occurs at some sites at Goss Moor NNR.
The species is at risk from land drainage, in-filling of ponds and ditches, alterations to river and stream channels and eutrophication.
It was added to the UK BAP list in 2007. Field surveys are required to ascertain the current status of the species in VC1.
I.J. Bennallick, S. Board, C.N. French, P.A. Gainey, C. Neil, R. Parslow, A. Spalding and P.E. Tompsett. eds. 2009. Red Data Book for Cornwall and the Isles of Scilly. 2nd Edition.Croceago Press.
The Cornish Red Data Book Project was led by the Cornwall and Isles of Scilly Federation for Biological Recorders (CISFBR). The full text and species accounts (minus the maps) are available on the CISFBR website.