Description: A small, solid shell mottled yellow or whitish on green. Has a large body whorl and large aperture closed by an operculum. Lives in hard water of lakes, canals and rivers, usually on stones or other solid support. 9-13 mm.

World Distribution: Ranges across Europe from the Pyrenees and Italy to coastal Finland and eastwards to the Caucasus. Distribution type: European Wide Temperate (63).

Irish Distribution: Widely distributed in central Ireland in slow-moving water or on lakeshores. It is recorded as far north-west as Glenade Lough, Sligo but is not in the Erne or Lough Neagh catchments (Kerney, 1968).

Ecology:

• Confined to well-oxygenated, usually flowing, water over calcareous bedrock
• Also occasionally on exposed lake shores in the west
• Prefers to settle and feed on rocks, walls or other solid support

Key Identification Features:

• A solid, dark green shell marbled and spotted with yellow or white.
• Body whorl massive with 1-2 apical whorls perched on top.
• Mouth wide, flattened, with a conspicuous broad white flange round the periphery to aid adhesion.
• Operculum, yellowish horn colour, thin but strong, translucent.

Red list status:

• Least concern (lc).

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

iNaturalist: Theodoxus fluviatilis at iNaturalist World Species Observations database.

GBIF data for Theodoxus fluviatilis | Classification: Gastropoda, Cycloneritida, Neritidae, Theodoxus

Thumbnails for genus Theodoxus