MolluscIreland - land and freshwater
  • Pisidium amnicum (O. F. Müller 1774) River pea shell
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Pisidium amnicum
© Dr Roy Anderson

Map hosted by the National Biodiversity Data Centre, Waterford
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The largest Pisidium species. Shell a triangular oval with low umbos in front of the middle. Surface with glossy periostracum and prominent, irregularly spaced concentric ribs. Colour greyish white to brown often with a greenish cast, particularly towards the ventral margin. Widespread in hard water river systems.

Key characteristics

  • Large for a Pisidium at 11 mm.
  • Shell fairly solid, a triangular oval shape
  • Umbos broad but not prominent
  • Shell ornamented by an irregular concentric sculpture
  • Colour greyish white to brown often with a greenish cast, glossy
  • Umbos often coated with a dull ferruginous deposit

Size

7-11 mm.

World Distribution

Found across the Palaearctic and Nearctic. Distribution type: Circumpolar Boreo-temperate (56).

Irish Distribution

Locally common in the centre and south-east and, more rarely, as far north as the Lough Erne and Lough Neagh catchments.

Ecology

  • Prefers relatively hard flowing water
  • Usually found on gravelly or sandy bottoms with a moderate flow
  • Relatively intolerant of pollution

Red List status

  • Least concern (lc).

Wikipedia link

Wikipedia page for Pisidium amnicum

 Anderson, R., (2016). Pisidium amnicum (O. F. Müller 1774). [In] MolluscIreland.
http://www.habitas.org.uk/molluscireland/species.asp?ID=61 Accessed on 2017-10-20.