> Promenetus exacuous (Say 1821)

> Habitat & Distribution
The range of Promenetus exacuousextends from Atlantic to Pacific Coasts of North America, from New Mexico, Nevada, and northern Texas to the Arctic-Boreal Transition Zone in Canada (Burch 1989, Jokinen 1992).  It occurs in quiet, shallow areas of lakes and rivers, as well as intermittent or permanent streams and ponds (Clarke 1981, Jokinen 1992, Jokinen 2005).  Here in the southern Atlantic drainages it has a very spotty distribution in the Coastal Plain, sharing habitat with migratory birds.

> Ecology & Life History
This species is associated with living or decaying plant matter of autochthonous or allocthonous origins, and rarely occurs in the absence of these resources (Clarke 1981, Harman 1982, Jokinen 1983, Jokinen 2005).  Substrata occupied include dead or living vegetation, mud, and occasionally rock (Clarke 1981, Jokinen 1992).  Promenetus exacuous inhabits both soft- and hard waters (Jokinen 1983, McKillop 1985, Dillon 2000).  Even in favorable situations, P. exacuous is rarely found in great abundance (McKillop 1985, Pip 1985, Pip 1991).  However, it is a good disperser and readily colonizes vegetation-rich habitats (Jokinen 1987).  The few life history studies focusing on this species revealed that P. exacuous is semelparous, with two cohorts produced each year (McKillop 1985, Jokinen 1992).  Although P. exacuous occurs in eutrophic systems, it is sensitive to environmental degradation (Clarke 1979).  Abundance and frequency of occurrence declined precipitously in southern Manitoba between 1978 and 1998 as intensive agriculture and other human land-use impacts increased (Pip 2000).  Similarly, P. exacuous was extirpated between from Oneida Lake (New York State) between 1968 and 1992, with hypereutrophication presumably causing this local extinction (Harman 2000).

> 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.   See Essay #2 below.  Synonyms of P. exacuous include Menetus exacuous, Menetus exacutus, and Planorbis exacutus (Stewart and Dillon 2004, Stewart 2006).

> Essay #1
Promenetus was featured in a November 2005 essay I posted to the FWGNA group on the aerial dispersal of freshwater gastropods.

> Essay #2
The Classification of the Planorbidae.  1 Figure.

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

> Maps of Promenetus 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. C. (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.  Burch, J.B. (1989) North American Freshwater Snails. Malacological Publications, Hamburg, Michigan.   Clarke, A.H. (1979) Gastropods as indicators of trophic lake stages. Nautilus 93:138-142.  Clarke, A.H.  (1981)  The Freshwater Molluscs of Canada. National Museum of Natural Sciences, National Museums of Canada, Ottawa, Canada.  Dillon, R.T., Jr. (2000) The Ecology of Freshwater Molluscs. Cambridge University Press, Cambridge, United Kingdom.  Harman, W.N. (1982) Benthic substrates: their effect on fresh-water Mollusca. Ecology 53: 271-277.  Harman, W.N. (2000)  Diminishing species richness of mollusks in Oneida Lake, New York State, USA. The Nautilus 114:120-126.  Hubendick, B.  (1955)  Phylogeny in the Planorbidae.  Trans. Zool. Soc. London 28: 453-542.  Jokinen, E.H. (1983) The Freshwater Snails of Connecticut. State Geological and Natural History Survey of Connecticut, Department of Environmental Protection Bulletin 109, Hartford, Connecticut.  Jokinen, E.H. (1987) Structure of freshwater snail communities: species-area relationships and incidence categories. American Malacological Bulletin 5:9-19.  Jokinen, E.H. (1992) The Freshwater Snails (Mollusca: Gastropoda) of New York State. New York State Museum Bulletin 482, Albany, New York.  Jokinen, E.H. (2005) Pond molluscs of Indiana Dunes National Lakeshore: then and now. American Malacological Bulletin 20:1-9.  McKillop, W.B. (1985) Distribution of aquatic gastropods across the Ordovician dolomite – Precambrian granite contact in southeastern Manitoba, Canada. Canadian Journal of Zoology 63:278-288.  Pip, E. (1985) The ecology of freshwater gastropods on the southwestern edge of the Precambrian Shield. The Canadian Field-Naturalist 99: 76-85.  Pip, E. (1991) Macrophyte and associated mollusc communities in a Meteor Crater Lake on the Precambrian Shield of Manitoba. The Canadian Field-Naturalist 105: 483-487.  Pip, E. (2000) The decline of freshwater molluscs in southern Manitoba. The Canadian-Field Naturalist 114:555-560.  Stewart, T.W., and R.T. Dillon, Jr. (2004) Species composition and geographic distribution of Virginia’s freshwater gastropod fauna: a review using historical records. American Malacological Bulletin 19:79-91.  Stewart, T.W. (2006) The freshwater gastropods of Iowa (1821-1998): species composition, geographic distributions, and conservation concerns. American Malacological Bulletin 21: 59 - 75.