FWGNA > Species Accounts > Viviparidae > Campeloma decisum
Campeloma decisum (Say 1817)
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> Habitat & Distribution

Combined with all its probable synonyms, Campeloma decisum ranges throughout eastern North America, well up into Canada and down to Florida.  The species is widespread throughout our study area, both in Atlantic drainages (below) and in drainages of the Tennessee.  Campeloma populations seem to reach maximum abundance burrowing in sandy bottoms where the current is sufficient to oxygenate the water column, especially in the larger rivers of the Piedmont and upper Coastal Plain.  They are not commonly found in small rocky streams, nor in lentic environments where summer temperatures might become extreme.  FWGNA incidence rank I-5.click map to view larger

> Ecology & Life History

Little is known regarding the diet of Campeloma.  The burrowing habit and peculiar radular morphology displayed by these snails imply an ability to filter feed, as has been documented for Viviparus.  But the snails have almost certainly retained the ability to graze or harvest deposits on soft sediments as well. There are reports that Campeloma can be baited with carrion.

Parthenogenesis has evolved three times in the freshwater Gastropoda, all three occasions (Campeloma, Potamopyrgus, and the thiarids) in ovoviviparous brooders (Dillon 2000:109). Some populations of Campeloma appear comprised entirely of parthenogenic females, others appear to reproduce entirely by outcrossing, and some populations display a mixture of the two modes (Johnson & Bragg 1999, Johnson & Leefe 1999, Johnson 2000, Crummett & Wayne 2009). 

Only a single year is required for maturation in some populations, two in others, and both semelparous and iteroparous reproduction have been reported (Vail 1978, Brown et al. 1989, Brown & Richardson 1992).  Jokinen’s (1983) analysis of the distribution of C. decisum in Connecticut and New York led her to classify it as an “A-B tramp,” typically present only in the more species-rich communities.  Dillon’s (2000: 360 - 363) reanalysis of these data suggested that C. decisum populations in Connecticut seem to be Undifferentiated with respect to life history adaptation.

> Taxonomy & Systematics

The first species of American Campeloma to reach description was decisum, authored by Thomas Say from his collections in the Delaware River. A great many nomena were added in the 19th and early 20th century, boiled down to 14 by Clench (1962) and further reduced to 8 by Burch (1989). 

The widespread occurrence of parthenogenesis in this group voids the biological species concept and necessitates a retreat to the morphological. In his extensive survey of genetic divergence among southern Campeloma populations, S. G. Johnson (1992, 2000, Johnson & Bragg 1999) has applied the nomina "decisum" and "limum" to samples from Atlantic drainages.  But Johnson has personally communicated to us that the shell morphological traits by which he has distinguished these two taxa were generally weak and variable.  We agree.  We are entirely unable to distinguish Campeloma populations throughout our study area from typical C. decisum

Synonyms include brevispirum, coarctatum, cornea, crassulum, decisa, dissimilis, exilis, gibba, heros, integra, integrum, leptum, lewsi, limosa, milesi, milesii, obesum, ponderosum, rufum, subsolida, subsolidum, subsolidus, and tannum.  Alternate genera include Melantho, Paludina, and Vivipara

> Supplementary Resources [PDF]

> References

Burch, J. B. (1989)  North American Freshwater Snails.  Malacological Publications, Hamburg, Michigan.  365 pp.
Brown, K.M. & Richardson, T. D. (1992) Phenotypic plasticity in the life histories and production of two warm-temperature viviparid prosobranchs. Veliger 35: 1-11.
Brown, K. M., Varza, D.& Richardson, T. D. (1989) Life histories and population dynamics of two subtropical snails (Prosobranchia:Viviparidae). J. N. Am. Benthol. Soc. 8: 222-228.
Chamberlain, N. A. (1958)  Life history studies of Campeloma decisum.  The Nautilus 72: 22 - 29.
Clench, W. (1962) A catalogue of the Viviparidae of North America with notes on the distribution of Viviparus georgianus, Lea. Occas. Pprs. on Mollusks, Mus. Comp. Zool. Harvard, 2, 261-87
Clench, W. & Fuller, S. (1965) The genus Viviparus in North America. Occas. Pprs. on Mollusks, Mus. Comp. Zool. Harvard, 2, 385-412.
Crummett, L. T. & M. L. Wayne (2009) Comparing fecundity in parthenogenetic versus sexual populatons of the freshwater snail Campeloma limum: is there a two-fold cost of sex? Invert. Biol. 128: 1 - 8.
Dillon, R. T., Jr. (2000)  The Ecology of Freshwater Molluscs.  Cambridge University Press, Cambridge, England. 509 pp.
Harvey, M., Vincent, B., & Vaillancourt, G. (1983) (Development and fecundity of Campeloma decisum (Say) (Gastropoda: Prosobranchia) in a cold climate.) Naturaliste Canadien 110: 335-342.
Imlay, M. J., Arthur, J.W., Halligan, B.J., & Steinmetz, J.H. (1981) Life Cycle of the Freshwater Snail Campeloma decisum (Viviparidae) in the Laboratory. Nautilus 95: 84-88.
Johnson, S. G. (1992) Spontaneous and hybrid origins of parthenogenesis in Campeloma decisum (freshwater prosobranch snail). Heredity 68: 253-261.
Johnson, S.G. & Bragg, E (1999) Clonal diversity and polyphyletic origins of hybrid and spontaneous parthenogenetic Campeloma (Gastropoda: Viviparidae) from the southeastern United States. Evolution 53: 1769-1781.
Johnson, S.G. & Leefe, W. R. (1999) Evolution and ecological correlates of uniparental reproduction in freshwater snails. J. Evol. Biol. 12: 1056-1068.
Johnson, S.G., Lively, C.M. & Schrag, S.J. (1995) Age and polyphyletic origins of hybrid and spontaneous parthenogenetic Campeloma (Gastropoda: Viviparidae) from the southeastern United States. Experientia (Basel) 51: 498-509.
Jokinen, E. (1983) The freshwater snails of Connecticut.  State Department of Environmental Protection Bulletin 109, 83 pp.
Jokinen, E. (1987) Structure of freshwater snail communities: Species-area relationships and incidence categories.  Amer. Malac. Bull. 5: 9 - 19.
Karlin, A.A., Vail, V.A. & Heard, W.H. (1980) Parthenogenesis and biochemical variation in southeastern Campeloma geniculum (Gastropoda: Viviparidae). Malacol. Rev., 13: 7-15.
Richardson, T.D. & Brown, K.M. (1989) Secondary production of two subtropical snails (Prosobranchia:Viviparidae). J. N. Am. Benthol. Soc. 8: 229-236.
Selander, R.K., E.D. Parker & R.A. Browne (1977)  Clonal variation in the parthenogenetic snail Campeloma decisa (Viviparidae)  Veliger 20: 349-351.
Vail, V.A. (1977) Comparative reproductive anatomy of 3 viviparid gastropods. Malacologia 16: 519-520.
Vail, V.A. (1978) Seasonal reproductive patterns in 3 viviparid gastropods. Malacologia 17: 73-97.