Narrow-mouthed Whorl Snail

Narrow-mouthed whorl snail (Vertigo angustior) is a tiny brown snail that can be found in undisturbed marshy coastal grassland and coastal turf fed by seepages. It is classed as Vulnerable on the Irish Red list, is a UK and Northern Ireland Priority Species that is listed in the EU Habitats Directive. The Irish populations are of global importance.

Fast Facts

Latin name: Vertigo angustior

Notable feature: Whorl snails are a group of species that can look very similar and so can be difficult to identify. These very small snails have peculiar outgrowths called “teeth” at the entrance of their shells. These teeth are designed to prevent predators from entering the shell and killing the animal. How the teeth are arranged can be used to separate one species from another.

Rarity in the UK: Rare / Common

Where in the UK: This was once a widespread species that is now very local and rare in Ireland and the British Isles as a whole. In Northern Ireland it is recorded from a small area on the Causeway coast in Antrim. It is also abundant as a subfossil in dune pockets along the north coast.

Vertigo angustior (c) Roy Anderson

A perfect home

The Narrow-mouthed whorl snail is usually found in areas of dune grassland, dune slacks and undisturbed marshes. It can be found near the shore in tussocky grassland and coastal turf that is fed by freshwater seepages.

Lifecycle

The adult snails are present at all times of the year and are usually found in the roots or on the stems of grass tussocks and also on flotsam close to the upper shore. The snail can often be found attached to the underside of rocks and driftwood in this area.

Not much is known about the lifecycle of this species though the population size appears to increase later in the year.

Why does this snail need help?

The main threat to the snail is likely eutrophication leading to the deterioration of water quality in coastal seepages. Coastal development and drainage schemes also threaten this species

What is Buglife doing to help?

Buglife are working with the National Trust to complete targeted surveys of the Narrow-mouthed whorl snail at several sites near the Giant’s Causeway throughout the year. This survey aims to gather population and distribution data that will help with designing a monitoring methodology for the species. More information on the project can be found here.

References and further information

  • Anderson, R., (2016). Vertigo (Vertilla) angustior Jeffreys 1830. [In] MolluscIreland. http://www.habitas.org.uk/molluscireland/species.asp?ID=188  Accessed on 2020-01-26.
  • Byrne, A., Moorkens, E.A., Anderson, R., Killeen, I.J. & Regan, E.C. (2009) Ireland Red List No. 2 – NonMarine Molluscs. National Parks and Wildlife Service, Department of the Environment, Heritage and Local Government, Dublin, Ireland.
  • Cameron, R.A.D. (2003). Land snails in the British Isles. Field Studies Council, Aidgap Key OP79.
  • Holyoak, G.A. (2005). Vertigo angustior (Mollusca: Gastropoda) at the Giant’s Causeway, Co Antrim. Irish Naturalists’ Journal 28: 176.
  • National Museums Northern Ireland; Text written by Dr Roy Anderson (2006-18). Northern Ireland Priority Species; Vertigo angustior – narrow-mouthed whorl snail http://www.habitas.org.uk/priority/species.asp?item=6675  Accessed October 2018.
  • Norris, A. and Colville, B. (1974). Notes on the occurrence of Vertigo angustior Jeffreys in Great Britain. J. Conch. Lond. 28: 141-154.
  • Ross, H.C.G. (1984). Catalogue of the land and freshwater Mollusca of the British Isles in the Ulster Museum. Ulster Museum, Belfast.
  • Standen (1897). The land Mollusca of Ballycastle and district, Co. Antrim. Irish Naturalist 6: 1-28.
  • Welch, R.J. (1898) Land-shell pockets on sand-dunes. Irish Naturalist 7: 72-82.