Description: A small, operculate shell, conical in shape with moderately convex whorls and invariably coated with a dark, matt deposit. Animal dark with greyish tentacles a narrow cone of white down the centre. Introduced from New Zealand in the 19th century. 4-5.5 mm.

World Distribution: Native to South Island, New Zealand but transported by human activities to Europe where it is still spreading in fresh and brackish waters.

Irish Distribution: Probably introduced to Irish freshwaters early in the nineteenth century. Stelfox and Welch (1980) report the finding of a shell in the Hyndman (now Ulster Museum) Collection, labelled "Lough Neagh, --18--"; which Stelfox thought referred to around 1837 (see Stelfox, 1926). This is substantially earlier than the first British record of 1859, for Gravesend. It was first formally brought forward as Irish by Adams (1897), from the Lough Neagh outflow of the Lower Bann. It has since become one of the most widespread molluscs in Irish freshwaters.

Ecology:

• Can occur almost anywhere, except for stagnant ponds, temporary water bodies, isolated lakelets and peaty habitats
• Especially widespread in clear streams, where these flow into the sea or into larger lake systems
• Can also occur in brackish water up to about 8‰ where a low-spired, broadly conical form prevails

Key Identification Features:

• Small, operculate shell of typical hydrobiid shape i.e. narrowly conical
• Whorls moderately convex with deep sutures
• Shell glossy pale brown but invariably coated with a dark, matt deposit
• Animal dark grey with pale grey tentacles showing a narrow white streak down the centre

Red list status:

• Not applicable.

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

iNaturalist: Potamopyrgus antipodarum at iNaturalist World Species Observations database.

GBIF data for Potamopyrgus antipodarum | Classification: Gastropoda, Littorinimorpha, Tateidae, Potamopyrgus

Thumbnails for genus Potamopyrgus