> Valvata bicarinata (Lea 1841)

> Habitat & Distribution
Valvata bicarinata has been reported from rivers and lakes in scattered eastern and midwestern North American states, including Illinois, Iowa, New Jersey, Pennsylvania, Tennessee, Alabama, Georgia, and North Carolina (Walker 1906, Burch 1989, Stewart 2006). We have documented two populations in Georgia and one population in the northeast corner of North Carolina, at Wiccacon Creek.

> Ecology & Life history
Knowledge of the ecology and life history of this species is limited. Valvata bicarinata is at least somewhat sensitive to environmental degradation; this species became extinct in Oneida Lake, New York State, following some years of artificial eutrophication (Harman 2000). V. bicarinata is monecious (Clarke 1981, Brown 2001). The spherical egg capsules contain 1-60 eggs, and developing embryos are green (Clarke 1981).

> Taxonomy & Systematics
Valvata species are notoriously polymorphic, and Valvata bicarinata is no exception (Walker 1906, Burch 1989). A single population can contain multiple morphological variants (Burch 1989). Whereas typical V. bicarinata have two spiral carinae or angulations on the shell, a morph (variety normalis) with three carinae also exists (Burch 1989). Additional phenotypic forms of V. bicarinata may also occur, and species misidentifications are likely common (Walker 1906).

> Essay
I mentioned the Wiccacon Creek population of Valvata bicarinata in my essay of 17Nov05 on the aerial dispersal of freshwater gastropods.

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



North Carolina (PDF) 

Georgia (PDF)

> References
Brown, K.M. 2001. Mollusca: Gastropoda. In: J.H. Thorp and A.P. Covich, eds., Ecology and Classification of North American Freshwater Invertebrates, Academic Press, New York. Pp. 297-329. Burch, J.B. 1989. North American Freshwater Snails. Malacological Publications, Hamburg, Michigan. Clarke, A.H. 1981. The Freshwater Molluscs of Canada. National Museum of Natural Sciences, National Museums of Canada, Ottawa, Canada. Harman, W.N. 2000. Diminishing species richness of mollusks in Oneida Lake, New York State, USA. Nautilus 114:120-126. Heard, W. H. 1963. Reproductive features of Valvata. Stewart, T.W. 2006. The freshwater gastropods of Iowa (1821-1998): species composition, geographic distributions, and conservation concerns. Amer. Malac. Bull. 21: 59 – 75. Walker, B. 1906. Notes on Valvata. Nautilus 20:25-32.