> Helisoma anceps (Menke 1830)

> Habitat & Distribution
H. anceps ranges throughout most of North America, from western Canada to the southeastern United States.  It is typically found in waters with at least a little current, and is more common on solid substrates than its congener H. trivolvis.  It is also not as typical of rich or eutrophic environments as H. trivolvis.  Populations of H. anceps extend from the mountains to the coastal plain, but are especially common in the Piedmont ecoregion.

> Ecology & Life history
Helisoma anceps is smaller and more benthic than the better-known H. trivolvis, at least here in the southern Atlantic drainages, and hence seems more the grazer and less the browser of macrophytes.  For an ecological comparison of the two species in Canada see Pip (1987).   Reproduction is annual and semelparous, at least in the better-studied northern populations (Herrmann & Harman 1975, Jokinen 1985).  Like all planorbids, H. anceps supports an ample share of predators (Brown & Strouse 1988, Weber & Lodge 1990) and trematode parasites (Fernandez & Esch 1991, Esch et al. 1997, Zelmer & Esch 1998). 

> Taxonomy & Systematics
The classification of the Planorbidae proposed by the tag team of Baker (1945) and Hubendick (1955) remains, after 50 years, the basis for our understanding of this large and diverse family of pulmonates worldwide.  Helisoma anceps is distinct and well-characterized.  To my knowledge there has been no confusion regarding its identification or systematic placement.  Helisoma antrosa is a common synonym.

> Essay #1
The Classification of the Planorbidae.  1 Figure.

> Hubendick (1955)
classification of the Planorbidae, applied to North America.

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



North Carolina (PDF)

South Carolina (PDF)

Georgia (PDF)

>References
Baker, F. (1945) The Molluscan Family Planorbidae. Urbana: University of Illinois Press.  Baker, H. B. (1946) Index to F.C. Baker's "The Molluscan Family Planorbidae." Nautilus, 59, 127-41. Brown, K., & B. Strouse (1988) Relative vulnerability of six freshwater gastropods to the leech Nephelopsis obscura (Verrill). Freshw. Biol., 19: 157-165. Cummins, K., & G. Lauff (1969)  The influence of substrate particle size on the microdistribution of stream macrobenthos. Hydrobiologia, 34: 145-181. Esch, G.W.,  Wetzel, E.J., Zelmer, D.A. & Schotthoefer, A.M. (1997) Long-term changes in parasite population and community structure: A case history.  Am. Midl. Nat. 137: 369-387. Fernandez, J. & Esch, G.W. (1991)  The component community structure of larval trematodes in the pulmonate snail Helisoma anceps.  J. Parasitol. 77: 540-550. Herrmann, S. A. & Harman, W. N. (1975) Population studies on Helisoma anceps (Menke) (Gastropoda: Planorbidae).  Nautilus 89: 5-11. Hubendick, B.  (1955)  Phylogeny in the Planorbidae.  Trans. Zool. Soc. London 28: 453-542. Jokinen, E.  (1985) Comparative life history patterns within a littoral zone snail community. Verh. Internat. Verein, Limnol., 22: 3292-3399. Laman, T., N. Boss, & H. Blankespoor (1984)  Depth distribution of seven species of gastropods in Douglas Lake, Michigan. Nautilus, 98: 20-24. Pip, E. (1987)  Ecological differentiation within genus Helisoma (Gastropoda: Planorbidae) in central Canada.  Nautilus101: 33-44. Weber, L.M. & Lodge, D.M. (1990) Periphytic food and predatory crayfish: Relative roles in determining snail distribution.  Oecologia 82: 33-39. Zelmer, D.A. & Esch, G.W. (1998) Bridging the GAP: The odonate naiad as a paratenic host for Halipegus occidualis (Trematoda: Hemiuridae).  J. Parasitol. 84: 94-96.