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.
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).
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.
The genus Gyraulus occurs worldwide, with the subgenus Gyraulus found throughout Australia.
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.
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.
Hubendick, B. (1955). Phylogeny of the Planorbidae. Transactions of the Zoological Society of London 28: 453-542.
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.