> Lyogyrus granum (Say 1822)
    "Amnicola (Lyogyrus) grana" 

> Habitat & Distribution
Burch gave the range of L. granum as “Atlantic drainages in southeastern Pennsylvania and New Jersey to the headwaters of the Pearl River, Mississippi.” The species has been recorded as far north as Connecticut, however (Jokinen 1983).  Interestingly, Jokinen quoted a personal communication from F. G. Thompson giving the range of L. granumas extending from New England south only to North Carolina.  The species is indeed common and widespread in North Carolina, but we have quite a few records of the species through South Carolina and Georgia as well, all in ponds or slow rivers of the Coastal Plain.  Given the diminutive stature of the animals, many additional populations have almost certainly been overlooked.

> Ecology & Life history
I am unaware of any good ecological study involving this easily-neglected species.  Jokinen reported an annual life cycle for one population inhabiting a Connecticut pond.  The population dynamics of L. granum may be unusually “flashy,” especially for a prosobranch.  Although I made many collecting trips to the Salkehatchie River east of Yemassee over several years without observing a single specimen, in March of 2004 Lyogyrus granum suddenly became the most common gastropod at that site.

> Taxonomy & Systematics
Although Thompson (1968) and Burch (1980, 1982) considered Lyogyrus (Gill 1863) to be a subgenus under Amnicola, most workers today accord the taxon full genus rank.  Thompson & Hershler (1991) provided a couple figures of L. granum incidental to their description of two new amnicolines from Georgia, swinging back to the use of Lyogyrus as a full genus in the process.  Lyogyrus retromargo (Thompson 1968) is a synonym.

> Essay
My 26May04 essay on Somatogyrus also included notes on Lyogyrus and a photo comparing the several South Carolina hydrobiids.

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



North Carolina (PDF)

South Carolina (PDF) 

Georgia (PDF)

> References
Jokinen, E. H. (1983)  The freshwater snails of Connecticut.  State Dept of Environmental Protection Bulletin 109, 83 pp. Thompson, F. G. (1968)  The aquatic snails of the family Hydrobiidae of peninsular Florida.  University of Florida Press, Gainesville.  268 pp. Thompson, F. G. & R. Hershler (1991)  Two new hydrobiid snails (Amnicolinae) from Florida and Georgia, with a discussion of the biogeography of freshwater gastropods of south Georgia streams.  Malac. Rev. 24: 55-72.