MolluscIreland - land and freshwater
  • Pisidium obtusale (Lamarck 1818) Porous-shelled pea mussel

Map hosted by the National Biodiversity Data Centre, Waterford
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A very tumid shell of an angular, oval shape with broad, rounded umbos behind the mid point. Surface glossy with fine concentric striae. Numerous pores are visible inside the shell. Colour whitish to yellowish often coatred with a red-brown deposit. Widespread.

Key characteristics

  • A small, tumid shell with rounded umbos behind the mid point creating an angular shape
  • Surface very porous but glossy with fine concentric striae
  • Colour whitish to yellowish
  • Often coated with a red-brown deposit



World Distribution

Distribution type: Circumpolar Wide-temperate (66).

GBIF distribution map [open in new tab]

Irish Distribution

Widely distributed but somewhat localised by its habitat preferences.


  • Predominantly in habitats of small size
  • Characteristic of marshes, marsh drains, flooded margins of lakes and rivers and peaty pools in the uplands

Red List status

  • Least concern (lc).

Wikipedia link

Wikipedia page for Pisidium obtusale

 Anderson, R., (2016). Pisidium obtusale (Lamarck 1818). [In] MolluscIreland. Accessed on 2024-07-13.