Narrow-mouthed whorl snail (Vertigo angustior)

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Narrow-mouthed whorl snail fact file

Narrow-mouthed whorl snail description

KingdomAnimalia
PhylumMollusca
ClassGastropoda
OrderStylommatophora
FamilyVertiginidae
GenusVertigo (1)

The shell of the narrow-mouthed whorl snail (Vertigo angustior) is pale yellow-brown in colour with many thin growth ridges and 5 whorls. The mouth of the shell has five to six teeth and is thickened (2). The shell is sinistral, which means the body whorls are coiled in a clockwise direction with the mouth opening on the left-hand side of the body (4).

Size
Shell width: 0.9 mm (2)
Shell height: 1.8 mm (2)
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Narrow-mouthed whorl snail biology

Little is known of the biology of this species. Recent studies indicate an annual life-cycle with reproduction taking place mainly in late summer. In common with most members of the genus, the narrow-mouthed whorl snail is believed to feed on micro-fungi growing on dead and decaying plant remains (6).

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Narrow-mouthed whorl snail range

This species is widely distributed but threatened in central Europe, and extends north to southern Norway and Sweden (5). The narrow-mouthed whorl snail is one of Britain's rarest land snails (5), and is currently known from just twelve scattered sites in the UK (4).

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Narrow-mouthed whorl snail habitat

Inhabits un-shaded short, damp grass, moss or short herbs on marshes (3) or amongst leaf litter on limestone pavement (4). The largest population of the narrow-mouthed whorl snail in the UK occurs where freshwater seeps onto the margins of a saltmarsh, but in Europe the most frequent habitat is calcareous fenland (5).

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Narrow-mouthed whorl snail status

The narrow-mouthed whorl snail is classified as Near Threatened (NT) on the IUCN Red List (1), Endangered on the GB Red List and included in Annex II of the EC Habitats Directive (3).

IUCN Red List species status – Near Threatened

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Narrow-mouthed whorl snail threats

Although the reasons for the rarity of this snail are not known (7), it seems that the main factors involved are the sensitivity of its habitat to changes in hydrological conditions, physical disturbance and changes in the grazing regime (3). At one site in Suffolk, shading by reed canary grass (Phalaris arundinacea) and tall herbs may have contributed to a local decline in the species (7).

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Narrow-mouthed whorl snail conservation

The tiny narrow-mouthed whorl snail has been identified as a Priority species under the UK Biodiversity Action Plan (UK BAP). The Species Action Plan aims to maintain, protect and enhance all known populations. Three of the sites supporting this species are National Nature Reserves, a further five are designated Sites of Special Scientific Interest (SSSIs) or Areas of Scientific Interest (ASSIs). Four of the populations are designated features on candidate Special Areas of Conservation, a European site designation stemming from the EC Habitats Directive (4).

A research project funded by the Countryside Council for Wales into the ecology of this species and that of V. geyeri, another endangered snail, was completed in 2001 (8).

The UK Biodiversity Action Plan for this species is available at UK BAP.
View information on this species at the UNEP World Conservation Monitoring Centre.
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Find out more

See the website of the Countryside Council for Wales:
http://www.ccw.gov.uk/

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Authentication

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

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Glossary

Calcareous
Containing free calcium carbonate, chalky.
Whorls
In animals, the spiral or convolutions in the shell of a snail. In plants, a set of leaves, flowers, or branches that spring from a stem at the same point and encircle it.
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References

  1. IUCN Red List (August, 2012)
    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. Suffolk County Council. (Jan 2002):
    http://www.suffolkcc.gov.uk/e-and-t/countryside/biodiversity/action_plan/species/narrowsnail.html
  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.
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Image credit

Narrow-mouth whorl snail  
Narrow-mouth whorl snail

© Eva Sharland / National Museum of Wales

National Museum & Galleries of Wales
Biodiversity & Systematic Biology
National Museum & Galleries of Wales
Cathays Park
Cardiff
CF10 3NP
United Kingdom
Tel: +44 (0) 2920 573244
Fax: +44 (0) 2920 239829
Harriet.Wood@nmgw.ac.uk
http://www.nmgw.ac.uk

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