The Atlantic drainages of Georgia, comprising approximately 40% of the waters of the state, are presently covered... ›› more
The four ecoregions of North Carolina drain toward the Atlantic through six major river systems... ›› more
Although perhaps not as environmentally heterogeneous as neighboring states, South Carolina does include... ›› more
The survey reported here is focused on the eastern 75% of the state, draining from the Blue Ridge to the Atlantic... ›› more
All waters draining into the Tennessee River above the Alabama line, including SW Virginia, W North Carolina, and N Georgia... ›› more
A study area of approximately 150,000 km2, including Delaware, Maryland, New Jersey, eastern Pennsylvania and the West Virginia panhandle... ›› more
A survey of all waters draining into the Ohio River upstream from the mouth of the Tennessee/Cumberland at River Mile 920... ›› more
> Habitat & Distribution
Basch
(1963) gave the American range of Hebetancylus
excentricus
as Georgia, Florida and Texas only. It was first reported in
South Carolina by Harrison (1989). Here we extend the range
of H. excentricus
to include spotty records from ponds and river backwaters up the length
of the southern Atlantic Coastal Plain. Populations are
locally
common on submerged sticks, logs, and large items of organic
debris. Such a contagious distribution suggests dispersal by
migratory waterfowl. FWGNA incidence rank I-3p,
peripheral.
> Ecology & Life History
Turner & Corkum (1979) reported simple annual life cycles in several Louisiana populations of Hebetancylus (type A of Dillon 2000: 156-162), one bivoltine (type C) population and one trivoltine (perhaps Esii). Other life history observations are available in McMahon (1976). Harrison (1989) reported that some of the individuals he collected from his South Carolina were septate, suggesting that they may have passed a period of dry or otherwise harsh environmental condition in aestivation.
> Taxonomy & Systematics
The presence of an apex distinctly off midline is generally considered diagnostic for this species. McMahon (2004) reported, however, that shell shape varied to such an extent in one Oklahoma population of limpets that no positive assignment could be made between Hebetancylus and Laevapex. Subsequent genetic work showed McMahon's population to be Laevapex (Walther et al. 2006). "Hebetoncylus" is a commonly-encountered misspelling of the genus name.
> Maps and Supplementary Resources
> Essays
- Hebetancylus was mentioned prominently in my 17Nov05 post to the FWGNA blog, "The Aerial Dispersal of Freshwater Gastropods."
- See my post of 26Sept14 for good, comparative figures illustrating "The egg masses of freshwater pulmonate snails."
> References
Basch, P. (1963)
A review of the recent freshwater limpet snails of North America. Bull.
Mus. Comp. Zool. Harvard, 129, 399-461.
Dillon, R. T., Jr. (2000)
The Ecology of Freshwater Molluscs. Cambridge University
Press,
United Kingdom. 509 pp.
Harrison, J. R. (1989)
The
freshwater limpet Hebetancylus
excentricus (Morelet) in South Carolina
(Abstract). ASB Bulletin 36(2): 110.
McMahon, R. F.
(1976)
Growth, reproduction and life cycle in six Texan populations of two
species of fresh-water limpets. Am. Midl. Nat. 95:
174-185.
McMahon, R.F.
(2004) A
15-year study of interannual shell-shape variation in a population of
freshwater limpets. Amer. Malac. Bull. 19:101-
109.
Turner, H. M. &
K. C. Corkum (1979)
A seasonal and ecological survey of freshwater limpet snails
(Pulmonata: Ancylidae) and their digenetic trematode parasites in
southeastern Louisiana. Tulane Stud. Zool. Bot. 21: 67 –
89.
Walther, A. C., T. Lee,
J. B. Burch & D. O'Foighil (2006) E pluribus unum: A
phylogenetic and phylogeographic reassessment of Laevapex
(Pulmonata: Ancylidae), a North American genus of freshwater
limpets. Molec. Phyl. Evol. 40: 501 - 516.