Description: The largest Pisidium or Euglesa 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. 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

Key Identification Features:

• 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

Red list status:

• Least concern (lc).

Distribution Map from NBN: Pisidium amnicum at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Pisidium amnicum at iNaturalist World Species Observations database.

GBIF data for Pisidium amnicum | Classification: Bivalvia, Sphaeriida, Sphaeriidae, Pisidium

Thumbnails for genus Pisidium