Geyer's whorl snail (Vertigo geyeri)
Facts
| Kingdom | Animalia |
|---|---|
| Phylum | Mollusca |
| Class | Gastropoda |
| Order | Stylommatophora |
| Family | Vertiginidae |
| Genus | Vertigo (1) |
| Size |
Shell width: 1.2 mm (2) Shell height: 1.7-1.9 mm (2) |
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Status
Classified as Vulnerable on the IUCN Red List, Endangered on the GB Red List and included in Annex II of the EC Habitats Directive (3).
Description
Range
Until very recently this species was known in the UK from just two sites in England and one in Wales. Survey work has discovered over twenty further populations including sites in Scotland and Northern Ireland (4). In Europe it occurs in a handful of very scattered sites between northern Sweden, Ireland and south-east Germany and it has an extremely patchy, local distribution throughout this range (5).
Habitat
All known populations occur in calcareous flushes; small springs of lime-rich water (5).
Biology
This snail has an annual life-cycle, although some may survive into their second year. Up to 10 eggs are laid in late summer, taking two weeks to develop. Adult snails graze on algae and bacteria growing on decaying plant remains (7).
Threats
The causes of the decline have not been identified, but the snail is vulnerable to trampling, increased grazing and changes in hydrology (3).
Conservation
All occupied sites in England and Wales are Sites of Special Scientific Interest (SSSIs). Four sites (in north-east England, Perthshire, Wales and north west England) are candidate Special Areas of Conservation (SACs), a site designation that stems from the EC Habitats Directive (5). Geyer's whorl snail is a UK Biodiversity Action Plan (UK BAP) priority species, and as such has a Species Action Plan. This plan aims to maintain the current populations and conduct surveys in an attempt to pinpoint as yet undiscovered populations.
The Countryside Council for Wales funded a PhD project, studying the ecology of this species and that of V. angustior, another endangered whorl snail, which was completed in 2001 (6), (8).
The UK Biodiversity Action Plan for this species is available at
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Further Information
The UK BAP Species Action Plan is available at:
http://www.ukbap.org.uk
For more on the Countryside Council for Wales see:
http://www.ccw.gov.uk/
Authentication
Information authenticated by Adrian Fowles of the Countryside Council for Wales:
http://www.ccw.gov.uk
Calcareous: containing free calcium carbonate, chalky.
References
- UNEP-WCMC (Jan 2002):
http://quin.unep-wcmc.org - Kerney, M.P. & Cameron, R.A.D. (1979) A field guide to the land snails of Britain and north-west Europe. William Collins and Sons & Co Ltd, London.
- UK BAP Species Action Plan (Jan 2002):
http://www.ukbap.org.uk - Fowles, A. Countryside Council for Wales (July 2003) Pers. comm
- JNCC (Jan 2002):
http://www.jncc.gov.uk - National Museums and Galleries of Wales (Jan 2002):
http://www.nmgw.ac.uk/biosyb/mollusca/index.en.shtml - Cameron, R.A.D. et al. 2003. Species Accounts for snails of the genus Vertigo listed in Annex II of the Habitats Directive: V. angustior, V. genesii, V. geyeri and V. moulinsiana (Gastropoda, Pulmonata: Vertiginidae). Heldia, 5: 151-170.
- Cameron, R.A.D. 2003. Life-cycles, molluscan and botanical associations of Vertigo angustior and Vertigo geyeri (Gastropoda, Pulmonata: Vertiginidae). Heldia, 5: 95-110.
