MolluscIreland - land and freshwater
  • Aplexa hypnorum (Linnaeus 1758) Moss bladder snail
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Aplexa hypnorum
© Dr Roy Anderson
Aplexa hypnorum
© Dr Roy Anderson

Map hosted by the National Biodiversity Data Centre, Waterford
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A sinistral, dark red-brown to yellow-brown, highly polished shell with a tall, sharp spire and nearly flat sutures. Animal dark grey to almost black and lacking mantle digitations. Widespread but declining.

Key characteristics

  • A dark, sinistral, and rather beautiful shell
  • Highly polished and slippery in the hands
  • Animal dark grey to almost black lacking mantle (digitate) outgrowths
  • Spire relatively tall and sharp and whorls flattened with nearly flat sutures

Size

9-13 mm.

World Distribution

Confusion with allied species in North America and eastern Siberia has created uncertainty about the true distribution of this species. Present information suggests a Eurosiberian Boreo-temperate (54) or possibly Eurasian Boreo-temperate (55) range.

Irish Distribution

Very widespread but sporadic and decreasing in frequency in areas where agriculture is intensive.

Ecology

  • This beautiful shell with its flexuous dark-grey animal is confined to small, often temporary lowland habitats or the margins of larger water bodies subject to seasonal flooding
  • Before arterial drainage became an established feature of the landscape it was recorded widely from the flood plains of larger rivers but these habitats are now scarcer than formerly
  • Still relatively common, at least in northern counties, in the floodplains of larger lakes and on some rivers
  • Has been recorded from slightly saline conditions on a lagoonal inlet of the Co.Down coast at Strand Lough, Killough

Taxonomy

There are two curious records for small streams in Cos Down and Antrim where it has been found with the river limpet Ancylus fluviatilis. Specimens in these instances were small with a maximum length of 7.1 mm and with pale horn-coloured shells of 5 whorls. No name is available for this form and its origins and affinities are unknown.

Red List status

  • Vulnerable (VU).

Wikipedia link

Wikipedia page for Aplexa hypnorum

 Anderson, R., (2016). Aplexa hypnorum (Linnaeus 1758). [In] MolluscIreland.
http://www.habitas.org.uk/molluscireland/species.asp?ID=15 Accessed on 2017-10-18.