> Helisoma trivolvis (Say 1817)
    "Planorbella trivolvis"

> Habitat & Distribution
H. trivolvis ranges throughout North America, from arctic Canada to Florida, and has been introduced sporadically around the world.  This is the “ramshorn” snail commonly seen in the aquarium, and has doubtless been spread artificially by hobbyists and water gardeners.  It is not well adapted to lotic waters, in the southern Atlantic drainages being found primarily in lakes, ponds, swamps, and the calmest areas of coastal rivers.  It thrives in rich, eutrophic environments, and does not occur in especially acidic waters.

> Ecology & Life history
Helisoma trivolvis is a weedy species, R-selected in the sense of Dillon (2000: 123-135, 363, Eversole 1978).  It matures at an age of around 3 - 4 months in the laboratory, laying perhaps 20 - 40 eggs per week thereafter, depending on culture conditions (van der Schalie & Berry 1973).  Outcrossing is preferred but self-fertilization is possible (Paraense & Correa 1988).

The bulbous, planispiral shell of H. trivolvis typically enfolds a large pocket of air, rendering it positively buoyant, and thus it is commonly found among floating vegetation.  Helisoma trivolvis seems to have a stronger trophic apparatus than most freshwater snails; able to ingest macrophyte tissue and thriving on lettuce, as well as grazing rather nonspecifically on the periphyton (Smith 1989 a & b, Lombardo & Cooke 2002).  Its predators include leeches (Klemm 1975, Dillon 2000:303-304) and crayfish (Alexander & Covich 1991b).  It has played the white rat in several studies of community ecology (Boerger 1975, Brown 1982).

Helisoma trivolvis has served as a model organism for neurobiological studies (Bulloch & Ridgway 1989, Cole et al. 2002, Geddis & Rehder 2003), and its hemoglobin has attracted the attention of physiologists (Herskovits & Hamilton 1994).  It hosts a variety of trematode parasites (Sapp & Loker 2000, Fried & LaTerra 2002), including the worm that has recently become a pest in commercial catfish ponds (Venable, Gaude & Klerks 2000).

> Taxonomy & Systematics
Phenotypic plasticity in shell morphology can be striking in this species.  Essay #1 below reviews a striking case of gigantism, and Essay #2 details a population in Mt. Pleasant, SC, where individuals inhabiting the pond vegetation behind an earth dam bear slender shells (0.165 ratio height:diameter) while individuals inhabiting rip-rap rock surfaces below the dam bear stout shells (0.245 height:diameter).  Such variation has lead to a proliferation of species names, which were lowered to subspecific rank by Baker.

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.  Burch followed Taylor (1966) in promoting Baker's subgenus Planorbella to generic rank and moving trivolvis into it, but we disagree, for reasons outlined in Essay #3 below. 

> Essay #1
on gigantism in pulmonates, featuring H. trivolvis.  5 figures.

> Essay #2
on the effects of current and substrate on shell morphology in H. trivolvis.  3 Figures.

> Essay #3
The Classification of the Planorbidae.  1 Figure.

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

>Pretty photo
Living H. trivolvis, courtesy of Chris Lukhaup.

> 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. 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.  Boerger, H. (1975)  A comparison of the life cycles, reproductive ecologies, and size-weight relationships of Helisoma anceps, H.campanulatum, and H.trivolvis (Gastropoda, Planorbidae).  Can. J. Zool. 53: 1812-1824. 1975.  Brown, K.M. (1982)  Resource overlap and competition in pond snails: An experimental analysis.  Ecology: 63: 412-422.  Bulloch, A.G.M. & Ridgway, R.L. (1989)  Neuronal plasticity in the adult invertebrate nervous system.  J. Neurobiol. 20: 295-311.  Cole, A.G., Mashkournia, A., Parries, S.C. & Goldberg, J.I. (2002)   Regulation of early embryonic behavior by nitric oxide in the pond snail Helisoma trivolvis.  J. Exp. Biol. 205: 3143-3152.  Eversole, A.  (1978)  Life cycles, growth and population bioenergetics of the snail, Helisoma trivolvis (Say). J. Moll. Stud., 44: 209-222.  Fried, B. & LaTerra, R. (2002)  In vitro and in vivo encystment of the cercariae of Echinostoma caproni.  J. Parasitol. 88: 1124-1129.  Geddis, M.S. & Rehder, V. (2003) Initial stages of neural regeneration in Helisoma trivolvis are dependent upon PLA sub(2) activity.  J. Neurobiol. 54: 555-565.  Herskovits, T.T. & Hamilton, M.G. (1994)  The molecular weight and subunit organization of Helisoma trivolvis (Say) hemoglobin: Light-scattering and scanning transmission electron microscopic studies.  Comp. Biochem. Physiol. 107B: 433-441.  Hubendick, B.  (1955)  Phylogeny in the Planorbidae.  Trans. Zool. Soc. London 28: 453-542.  Lombardo, P & Cooke, G. D. (2002)  Consumption and preference of selected food types by two freshwater gastropod species.  Arch. Hydrobiol. 155: 667-685.  Mancia, M.R. & Fried, B. ( 1995)  Chemoattraction and dietary preferences of Helisoma trivolvis (Gastropoda: Planorbidae) for leaf lettuce and Tetramin.  Veliger 38: 73-75.  Paraense, W.L. & Correa, L.R. (1988)  Self-fertilization in the freshwater snails Helisoma duryi and Helisoma trivolvis.  Mem. Inst. Oswaldo Cruz. 83: 405-409.  Rowan, W. (1966)  Autumn migration of Helisoma trivolis in Montana. Nautilus 79: 108-109.  Sapp, K.K. & Loker, E.S.  (2000)  Mechanisms underlying digenean-snail specificity: Role of miracidial attachment and host plasma factors.  J. Parasitol. 86: 1012-1019.  Smith, D. (1989a)  Tests of feeding selectivity in Helisoma trivolvis (Gastropoda: Pulmonata). Trans. Am. Micros. Soc. 108: 394-402.  Smith, D.  (1989b)  Radula-tooth biometry in Helisoma trivolis (Gastropoda, Pulmonata): interpopulation variation and the question of adaptive significance. Can. J. Zool. 67: 1960-1965.  Stahl, T. & Lodge, D.M. (1990)  Effect of experimentally induced shell damage on mortality, reproduction and growth in Helisoma trivolvis (Say, 1816).  Nautilus 104: 92-95.  Taylor, D. W. (1966)  Summary of North American Blancan nonmarine mollusks.  Malacologia 4: 1 - 172.  van der Schalie, H., & E. Berry (1973)  The effects of temperature on growth and reproduction of aquatic snails. Sterkiana, 50: 1-92.  Venable, D.L., Gaude, A.P. III, & Klerks, P.L. (2000)  Control of the trematode Bolbophorus confusus in Channel Catfish Ictalurus punctatus ponds using salinity manipulation and polyculture with Black Carp Mylopharyngodon piceus.  J. World Aquacult. Soc. 31: 158-166.