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Snail (Gyraulus)

Taxonomic group

Planorbidae: Gyraulus

Diagnostic features

Gyraulus is a genus of small snails with shells coiled in a flat spiral. The shells are usually pale or semi-transparrent, although larger individuals may be covered in algae. There is no operculum (protective shield) covering the aperture (shell opening) when the animal withdraws. The common native G. corinna has no keel around the outside of shell, but an unknown species with a keel is also common in some areas.

Typical habitats

Gyraulus are most common in slow-flowing streams where they often attach to the surfaces of aquatic plants.


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

Indicator value

  • Hard bottom: 3
  • Soft bottom: 1.7

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

Gyraulus can be abundant in unshaded streams with abundant weeds or algae and relatively poor water quality. They have been assigned low tolerance values of 3 (hard bottom sites) and 1.7 (soft bottom sites).