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Snail (Lymnaea)

Taxonomic group

Lymnaeidae: Lymnaea

Diagnostic features

A few species of Lymnaea snails have been introduced to New Zealand fresh waters, sometimes accidentally with aquatic plants and sometimes deliberately as food for trout. The lymnaeids lack an operculum (protective shield) that covers the aperture (shell opening) when the animal withdraws. The aperture is on the right when facing toward you and when the spire points upwards. The introduced Lymnaea species are often much larger or more elongated than the native lymnaeid Austropeplea.

Typical habitats

Lymnaea species are most likely to be found in lakes, ponds and slow flowing streams.


Like most snails they are grazers, scraping biofilms from submerged surfaces.

Indicator value

  • Hard bottom: 3
  • Soft bottom: 1.2

The tolerance values (ranging from 0 to 10) give an indication of which are the sensitive taxa (values of 8 or more) and which are the tolerant taxa (values of 3 or less). For more information see: Indicator species

Lymnaea species can be found in waters of moderate to poor water quality. This genus has not been assigned tolerance values but the Lymnaeidae have low tolerance values of 3 (hard bottom sites) and 1.2 (soft bottom sites).