Print Fact Sheet
Gyraulus Charpentier, 1837

Diagnostic features

Shell small, less than 10 mm. Flat, open spiral, acutely keeled to angular to bluntly angular whorls; smooth or spirally ribbed shells; sunken upper whorls with concave undersides, with a widely open umbilicus. Shell lacking internal lamellae. Animal with thin pointed tentacles and a blunt snout. Native species have plain greyish or unpigmented animals and mantle. The introduced Gyraulus (Gyraulus) chinensis has a mottled mantle. Penis with a dagger-like chitinous stylet.

Classification

Class Gastropoda

Subclass Heterobranchia

Order Hygrophila

Superfamily Planorboidea

Family Planorbidae

Subfamily: Planorbinae

Genus Gyraulus Charpentier, 1837

Subgenus Gyraulus Charpentier, 1837

Pygmanisus Iredale, 1943 is treated as a subgenus of Gyraulus

Type species: Planorbis hispidus Draparnaud, 1805, designated by Dall, 1870 (=Planorbis albus Müller, 1774)

Original reference: Charpentier J. De (1837). Catalogue des mollusques terrestres et fluviatiles de la Suisse. Neue Denkschriften der allgemeinen Schweizerischen Gesellschaft für die gesammten Naturwissenschaften 1(2): 1-28.

Type locality: Bex, Switzerland.

Synonyms: Glyptanisus Iredale, 1943; Plananisus Iredale, 1943

Two subgenera are recognised in Australia, Gyraulus (Gyraulus) and Gyraulus (Pygmanisus).

Biology and ecology

On water weeds, leaves, wood and stones, etc., in ephemeral and permanent waterholes, ponds, lakes, springs, billabongs, sphagnum bogs, swamps and sluggish streams and rivers. Feeds on detritus. Egg mass presumably a jelly strip containing small eggs. Development direct.

Brown (1981, 1998, 2001) described the anatomy of the Australian species of this genus.

Additional information on the biology and ecology of members of this family can be found in Fauna of Australia, vol. 5B, p. 1072-1074.

Distribution

The genus Gyraulus occurs worldwide, with the subgenus Gyraulus found throughout Australia.

Notes

This genus consists of small discoidal freshwater snails, with a keeled to bluntly angular periphery

They can be distinguished from the somewhat similar Glacidorbidae by their flatter, brownish shells and their blunt snout, their eyes situated on the inner sides of the base of the tentacles (rather than in the middle of each base) and the lack of an operculum.

A few other genera of Planorbidae are similar to Gyraulus, the most important being the genus Biomphalaria Preston, 1910, some species of which are intermediate hosts of significant animal and human parasites, including one of the human blood flukes (Schistosoma mansoni). Biomphalaria differs from Gyraulus in its larger shell size (up to nearly 20 mm in diameter) and the penis lacks a chitinous stylet.

Further reading

Baker, F. C. (1945). The molluscan family Planorbidae. Urbana USA, University of Illinois Press.

Beesley, P. L., Ross, G. J. B. & Wells, A., Eds. (1998). Mollusca: The Southern Synthesis. Parts A & B. Melbourne, CSIRO Publishing.

Brown, D. S. (1981). Observations on the Planorbidae from Australia and New Guinea. Journal of the Malacological Society of Australia 5: 67-80.

Brown, D. S. (1998). Freshwater snails of the genus Gyraulus (Gastropoda: Planorbidae) in Australia: the taxa of Tasmania. Molluscan Research 19: 105-154.

Brown, D. S. (2001). Freshwater snails of the genus Gyraulus (Planorbidae) in Australia: taxa of the mainland. Molluscan Research 21: 17-107.

Hubendick, B. (1955). Phylogeny of the Planorbidae. Transactions of the Zoological Society of London 28: 453-542.

Ponder, W. F., Clark, S. A. & Dallwitz, M. J. (2000). Freshwater and estuarine molluscs: an interactive, illustrated key for New South Wales. Melbourne, CSIRO Publishing.

Smith, B. J. (1992). Non-marine Mollusca. Pp. i-xii, 1-408 in W. W. K. Houston. Zoological Catalogue of Australia, 8. Canberra, Australian Government Publishing Service.

Smith, B. J. and Kershaw, R. C. (1979). Field guide to the non-marine molluscs of south eastern Australia. Australian National University Press, Canberra, Australia.

Smith, B. J. & Kershaw, R. C. (1981). Tasmanian Land and Freshwater Molluscs. Hobart, University of Tasmania.