MolluscIreland - land and freshwater
  • Physa fontinalis (Linnaeus 1758) Common bladder snail
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Physa fontinalis
© Dr Roy Anderson
Physa fontinalis
© Dr Roy Anderson

Map hosted by the National Biodiversity Data Centre, Waterford
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A small, yellow-brown, sinistral shell with short, blunt spire. Shell slippery and highly polished. The animal is grey and outgrowths of the mantle partly cover the shell. These have finger-like lobes or digitations. Widespread and common.

Key characteristics

  • A small, sinistral, yellow-brown shell
  • Spire short and blunt
  • Animal dark grey with finger-like lobes or digitations of the mantle partly covering the shell in life
  • Shell fragile, polished and slippery


8-12 mm.

World Distribution

This species has a wide distribution in the western Palaearctic, but like Aplexa hypnorum, confusion with allied forms makes the eastern limits of its distribution uncertain. The range is probably Eurasian Boreo-temperate (55). Several ‘species’ found in North America may be conspecific in which case the range could be Circumpolar Boreo-temperate.

GBIF distribution map [open in new tab]

Irish Distribution

Widespread throughout Ireland but sparser in the west and north.


  • A fragile but active species usually of clear, weedy and slow-flowing or stagnant waters such as canals, slow rivers and moderate-sized lakes, or the sheltered margins of larger lakes
  • Tolerant of moderate eutrophication
  • The effect of incursions by alien Physidae has not been assessed but Kerney (1999) observed little effect upon populations in Britain, except at organically polluted sites

Red List status

  • Least concern (lc).

Wikipedia link

Wikipedia page for Physa fontinalis

 Anderson, R., (2016). Physa fontinalis (Linnaeus 1758). [In] MolluscIreland. Accessed on 2024-03-02.