> Somatogyrus virginicus Walker 1904

> Habitat & Distribution
This species was originally described from the Rapidan River in Virginia, and for many years believed endemic to that particular river system.  It has recently become clear, however, that S. virginicus ranges from Virginia through the Carolinas and into Georgia, but that it has been confused with other hydrobiid genera and repeatedly rediscribed under other specific nomena.  The species is moderately common in rivers and streams of the North Carolina and Georgia Piedmont, reaching into the upper Southeastern Plains.  Watson (2000) reported populations in the Ocmulgee and Savannah drainages, under various aliases.  I have documented two South Carolina populations inhabiting Piedmont creeks and one in a small river at the foot of the Blue Ridge.  Very recently (2005) I have had my attention called to a fourth South Carolina population inhabiting the upper Lynches River in Lancaster County. 

Solid substrate seems to be a key habitat requirement.  The snail is typically found in rocky riffles with good flow, often associated with the macrophyte Podostemum.

> Ecology & Life History
I unaware of any good study on any aspect the biology of Somatogyrus. 

> Taxonomy & Systematics
The Hydrobiidae is arguably the most diverse family of freshwater gastropods, displaying great anatomical as well as conchological variety.  Males of the genus Somatogyrus bear simple verges, with a single duct, and are thus classified in the subfamily Lithoglyphinae.  Burch divided Somatogyrus into two subgenera (Walkerilla and Somatogyrus s.s.) but later opinions suggest little basis for the distinction (Thompson 1984).  The 35 species listed by Burch doubtless include many synonyms.  Synonyms of S. virginicus include tenax (Thompson 1969), alcoviensis (Krieger 1972), and perhaps georgianus, pennsylvanicus, and rheophilus, among others.

> Essay
I posted a longer review of Somatogyrus, Amnicola, and Gillia in the southeast on 27May04, with a couple figures.

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



North Carolina (PDF)

South Carolina (PDF)

Georgia (PDF)

> References
Krieger, K. A. (1972)  Somatogyrus alcoviensis, a new gastropod species from Georgia (Hydrobiidae).  Nautilus 85: 120 – 125.  Thompson, F. (1969) Some hydrobiid snails from Georgia and Florida. Quart. J. Florida Acad. Sci. 32: 241-65.  Thompson, F. (1984) North American freshwater snail genera of the hydrobiid subfamily Lithoglyphinae.  Malacologia 25: 109-141.  Walker, B.  (1904)  New species of Somatogyrus.  Nautilus 17: 133-142.  Watson, C. (2000) Results of a survey for selected species of Hydrobiidae (Gastropoda) in Georgia and Florida.  In Freshwater Mollusk Symposia Proceedings, Part II, eds. Tankersley, Warmolts, Watters, Armitage, Johnson & Butler, pp. 233 - 244.  Columbus: Ohio Biological Survey.