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Guide to New Zealand's freshwater invertebrates
Snail
(
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.
Feeding
Like most snails they are grazers, scraping biofilms from submerged surfaces.
Indicator value
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).
