> Gyraulus parvus (Say 1817)

> Habitat & Distribution
G. parvus is widespread and common in North America generally, from Canada to Florida, Atlantic to Pacific. It seems especially well-adapted to lacustrine environments north of the glacial maximum, however, and is only of spotty occurrence in the southern Atlantic drainages.

> Ecology & Life history
Although superficially similar to M. dilatatus, G. parvus seems to be restricted to richer environments. Gyraulus populations have figured in a variety of ecological studies in northern lakes (Horst & Costa 1971, Sheldon 1987, Osenberg 1989) but are not well studied in the south. Jokinen (1987) characterized G. parvus as a “C-D tramp” in New England, characteristic of habitats occurring virtually everywhere she sampled. The Canadian population studied by McKillop (1985) displayed a simple annual life cycle (A).  The effect of fish predation on G. parvus populations has been investigated by Martin et al. (1992) and Thorp & Bergey (1981).

> Taxonomy & Systematics
The classification of the Planorbidae proposed by the tag team of Baker (1945) and Hubendick (1955) remains, after 50 years, the basis for our understanding of this large and diverse family of pulmonates worldwide.   Gyraulus parvus is taxonomically well-characterized and has remained systematically stable. 

Essay #1
The Classification of the Planorbidae.  1 Figure.

> Hubendick (1955)
classification of the Planorbidae, applied to North America.

> Maps of Gyraulus distribution
Click the small map to enlarge it, or download the state-specific PDFs



North Carolina (PDF)

South Carolina (PDF)

Georgia (PDF)

> References
Baker, F. (1945) The Molluscan Family Planorbidae. Urbana: University of Illinois Press.  Baker, H. B. (1946) Index to F.C. Baker's "The Molluscan Family Planorbidae." Nautilus, 59, 127-41. Horst, T. & R. Costa ( 1971) Distribution patterns of five selected gastropod species from McCargo Lake. Nautilus, 85: 38-43. Hubendick, B.  (1955)  Phylogeny in the Planorbidae.  Trans. Zool. Soc. London 28: 453-542.  Jokinen, E.  (1987)  Structure of freshwater snail communities: species-area relationships and incidence categories. Am. Malacol. Bull., 5: 9-19. Martin, T., L. Crowder, C. Dumas, & J. Burkholder (1992) Indirect effects of fish predation on macrophytes in Bays Mountain Lake: Evidence for a littoral trophic cascade. Oecologia, 89: 476-81. McKillop, W. (1985) Distribution of aquatic gastropods across the Ordovician dolomite – Precambrian granite contact in southeastern Manitoba. Can. J. Zool., 63: 278-88. Osenberg, C. (1989) Resource limitation, competition and the influence of life history in a freshwater snail community. Oecologia, 79: 512-19. Sheldon, S, P. (1987) The effects of herbivorous snails on submerged communities in Minnesota lakes. Ecology, 68: 1920-31. Thorpe, J. & E. Bergey (1981) Field experiments on responses of a freshwater benthic macroinvertebrate community to vertebrate predators. Ecology, 62: 365-75.