Geyer's whorl snail (Vertigo geyeri)

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)

Geyer's whorl snail is classified as Least Concern (LC) on the IUCN Red List (1), Endangered on the GB Red List and included in Annex II of the EC Habitats Directive (3).

The tiny Geyer's whorl snail is quite similar in appearance to Vertigo genesii but has a more conical shell (2). The shell is pale reddish-brown with regular growth-lines, and the mouth typically has four small peg-like teeth but may have fewer (2).

Until very recently Geyer's whorl snail 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).

All known Geyer's whorl snail populations occur in calcareous flushes; small springs of lime-rich water (5).

This snail has an annual life-cycle, although some may survive into their second year. Up to ten eggs are laid in late summer, taking two weeks to develop. Adult Geyer's whorl snails graze on algae and bacteria growing on decaying plant remains (6).

The causes of the decline have not been identified, but Geyer's whorl snail is vulnerable to trampling, increased grazing and changes in hydrology (3).

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 Geyer's whorl snail and that of V. angustior, another endangered whorl snail, which was completed in 2001 (7), (8).

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/

Information authenticated by Adrian Fowles of the Countryside Council for Wales:
http://www.ccw.gov.uk

• Algae: simple plants that lack roots, stems and leaves but contain the green pigment chlorophyll. Most occur in marine and freshwater habitats.
• Calcareous: containing free calcium carbonate, chalky.

1. IUCN Red List (May, 2011)
   http://www.iucnredlist.org/
2. 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.
3. UK BAP Species Action Plan (Jan 2002):
   http://www.ukbap.org.uk
4. Fowles, A. Countryside Council for Wales (July 2003) Pers. comm
5. JNCC (Jan 2002):
   http://www.jncc.gov.uk
6. 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.
7. National Museums and Galleries of Wales (Jan 2002):
   http://www.nmgw.ac.uk/biosyb/mollusca/index.en.shtml
8. Cameron, R.A.D. 2003. Life-cycles, molluscan and botanical associations of Vertigo angustior and Vertigo geyeri (Gastropoda, Pulmonata: Vertiginidae). Heldia, 5: 95-110.