> Gillia altilis (Lea 1841)

> Habitat & Distribution
The type locality for G. altilis was the Santee Canal, an early nineteenth century passage between Charleston and the Santee River to the north, now obliterated under the waters of Lake Moultrie. For many years I was unable to confirm a single occurrence of Gillia in its native state. But in early 2005 I rediscovered a small but apparently healthy population of the species in the Lynches River south of Florence.  The essay I composed on the occasion (#1) is reachable from the link below.

Gillia in the Lynches River shows similar habitat preferences to the sparse Goniobasis catenaria population with which it co-occurs, strongly associated with rip rap rocks and hard clay islands in an environment characterized by mud and sand. It seems likely that the range of the species in South Carolina may have been severely impacted by erosion and sedimentation.

Fortunately, G. altilis is much more common in the coastal plain rivers of North Carolina.  Walker (1918) gave the American range of the species as New Jersey to South Carolina, but Jokinen (1992) confirmed it from as far north as Vermont and west to Lake Ontario.  Thompson (1984) suggested that the Lake Ontario population may have been introduced artificially, through the Erie Canal. Doug Smith (pers. comm.) reports an apparently healthy population of Gillia on the shores of Lake Champlain.  One cannot fail to be impressed by the remarkable breadth of adaptation displayed by any gastropod species able to inhabit environments as diverse as the big lakes of upstate New York and the sluggish blackwater rivers of the Carolina coastal plain.

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

> Essay #1
I posted an essay on the rediscovery of Gillia in South Carolina on 24Jan05.  A photo of the critter “on the hoof” is included.

> Essay #2
There’s a nice photo comparing Gillia to the three other hydrobiid snails found in South Carolina reachable from my earlier essay of 26May04.

> Taxonomy & Systematics
The Hydrobiidae is arguably the most diverse family of freshwater gastropods in North America, displaying great anatomical as well as conchological variety.  One might think that taxonomists working with a family containing a large number of species would tend not to erect monotypic genera, but it seems to me that the opposite is often the case.

The monotypic genus Gillia is characterized by a simple, single-ducted verge, and as such is classified with Somatogyrus and several other North American genera in the subfamily Lithoglyphinae. Its anatomy has been described by Thompson (1984).

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



North Carolina (pdf)

South Carolina (pdf)

> References
Jokinen, E.  (1992)  The freshwater snails (Mollusca: Gastropoda) of New York State. New York State Museum Bulletin 482: 1-112.  Thompson, F. (1984) North American freshwater snail genera of the hydrobiid subfamily Lithoglyphinae.  Malacologia 25: 109-141. Walker, B.  (1918)  A Synopsis of the Classification of the Freshwater Mollusca of North America, North of Mexico. Misc. Pubs., vol. 6. Ann Arbor, University of Michigan Press.