FWGNA > Species Accounts > Physidae > Physa acuta
Physa acuta Draparnaud 1805
“Physella heterostropha” 
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> Habitat & Distribution

Physa acuta is the most common and widespread freshwater gastropod inhabiting our entire 17-state study area, a title it could probably claim for North America, and quite possibly the world (Dillon et al., 2002).  Populations may inhabit any and all freshwaters whatsoever from the equator to boreal latitudes, but reach maximum densities in lentic environments, especially those that are rich, disturbed and/or artificially eutrophic.  FWGNA incidence rank I-5.

> Ecology & Life History

Physa acuta is a “weedy” or R-selected species, in the sense of Dillon (2000: 131-135). Its rapid maturation, high reproductive rate, and ease of culture have made it the “fruit fly of malacology,” spawning scores of detailed studies on life history (Clampitt 1970), behavior (McCarthy & Fisher 2000), competition (Kesler et al.1986, Martinez & Rogowski 2011), parasitism (Ebbs et al. 2018, Stoll et al. 2013) and predation (Crowl & Covich 1990, Alexander & Covich 1991, DeWitt et al. 1999, 2000, Dorn 2013).

Jokinen’s (1987) analysis of the distribution of P. acuta in Connecticut and New York (listed as P. heterostropha) led her to classify it as a “C-D tramp,” potentially present in nearly every community.  Dillon’s (2000: 360-363) reanalysis of these data suggested that P. acuta populations in Connecticut seem to be Undifferentiated with respect to life history adaptation.

Laboratory populations mature in 6 – 8 weeks, male function arriving slightly before female function, each adult laying 50 – 100 eggs weekly thereafter for up to a year (Wethington & Dillon 1993, Arendt 2015). They prefer to outcross, and can store allosperm for very long periods of time (Wethington & Dillon 1991, 1997).  But they self-fertilize successfully in isolation, and low levels of self-fertilization even seem to take place in females with proven allosperm reserves (Dillon et al. 2005a).  See Wethington & Dillon (1996) for a review of mating behavior.  If, after reading all the Dillon & Wethington references cited below, as well as essays 3Oct18 and 5Nov18, some question still remains in your mind regarding any aspect of the reproductive biology of P. acuta, please notify me and I will attend to it immediately.

> Taxonomy & Systematics

A detailed study of the shell morphology of Physa acuta, together with a review of ecology and life history of populations in Europe, has been contributed by Cieplok et al (2022).  Laboratory populations of P. acuta (under a variety of synonyms) have demonstrated significant ecophenotypic responses in shell shape both to temperature (Britton & McMahon 2004) and to the introduction of crushing predators (DeWitt 1998, Langerhans & DeWitt 2002, Auld & Relya 2011, Salice & Plautz 2011). The common garden experiments of Gustafson et al. (2014) returned evidence of striking morphological plasticity in the shell form of P. acuta correlated with the (many) environmental differences between stream and pond as well.  Against this background, the discovery of Dillon & Jacquemin (2015) that the heritability of (multivariate) shell morphology in Physa might range as high as h^2 = 0.819 was especially surprising (Essay 15Apr15).

Throughout the nineteenth and twentieth centuries, North American populations of Physa acuta were identified as P. heterostropha (Say 1817) in the east, P. integra (Haldeman 1841) in the midwest, P. virgata (Gould 1855) in the far west, and by a variety of additional Latin nomina more local in character everywhere around the USA.  Only in recent years has it been discovered that all of these populations are conspecific with each other, and with European populations apparently introduced from America in the late eighteenth century, previously described as Physa acuta (Dillon et al. 2002, 2005b, 2011, Lydeard et al. 2016).  See my entire series of essays "To Identify a Physa" 1971, 1975, 1978, 1989, and 2000 from the links below for a review of the malacological dawning. 

See Dillon & Wethington (1992, 1994) and Essay 5Nov18 for research on classical, transmission genetics in Physa acuta, and David et al. (2022) and Essay 9June22 for research on non-classical cytoplasmic male sterility.  Dillon & Wethington (1995, 2006) have contributed studies of the population genetics of P. acuta in North America and Bousset et al. (2004, 2014) similarly for Europe.  The allozyme study of Dillon (2018) suggested that the effective size of a Charleston-area Physa acuta population fluctuated between Ne = infinite and Ne = 50 over a period of 7 years (Essay 14Jan19).  Molecular phylogenetic studies have been contributed by Wethington & Lydeard (2007), Wethington et al. (2009), Ebbs et al. (2018) and Young et al. (2021).

Throughout the history of North American malacology, the classification of physid gastropods has been as problematic as their identification.  The system proposed by George Te (1978, 1980), published in Burch (1989), recognized 69 species and subspecies in four genera: Aplexa, Stenophysa, Physa and Physella, the last genus with three subgenera, Costatella, Petrophysa, and Physella (ss).  All of the physids common in our study area have at times been referred to the genus Physella

It is now clear that most of the nominal diversity previously recognized in the North American Physidae is attributable to phenotypic plasticity and that the true number of American species is closer to ten (Wethington 2004a, Wethington & Lydeard 2007).  The simple two-genus system favored by earlier workers (Walker, 1918) would seem sufficient (Essay 12Oct07). 

> Supplementary Resources [PDF]


  • Physa acuta stars in a YouTube video, with special thanks to Bobby Martin of Martin Microscopes!

> Essays

> References

Alexander, J., and A. Covich (1991)  Predator avoidance by the freshwater snail Physella
virgata in response to the crayfish Procambarus simulans.  Oecologia 87:435-442.
Arendt, J. (2015) Why get big in the cold? Size-fecundity relationships explain the temperature-size rule in a pulmonate snail (Physa). Journal of Evolutionary Biology 28: 169-178.
Auld J., and R. Relyea (2011)
  Adaptive plasticity in predator-induced defenses in a common freshwater snail: altered selection and mode of predation due to prey phenotype. Evolutionary Ecology 25: 189-202.
Bousset, L., P-Y. Henry, P. Sourrouille, & P. Jarne (2004)  Population biology of the invasive freshwater snail Physa acuta approached through genetic markers, ecological characterization and demography. Molec. Ecol., 13: 2023-2036.
Bousset, L., J-P. Pointier, P. David, and P. Jarne (2014) Neither variation loss, nor change in selfing rate is associated with the worldwide invasion of Physa acuta from its native North America. Biological Invasions 16: 1769-1783.
Burgarella, C. et al. (2015)  Molecular evolution of freshwater snails with contrasting mating systems.  Mol. Biol. Evol. 32(9): 2403 - 2416.
Buth, D. G., and J. J. Suloway (1983) Biochemical genetics of the snail genus Physa:  A comparison of populations of two species. Malacologia 23:351-359. 
Cieplok, A., R. Anderson, M. Gawlak, T. Kaluski, & A. Spyra (2022) Morphological diversification of alien and native aquatic snails of the genus Physa and Aplexa (Gastropoda: Physidae) of Western and Central European range.  Zootaxa 5168 (2): 101 - 118.
Clampitt, P. T. (1970) Comparative ecology of the snails Physa gyrina and Physa integra. Malacologia 10:113-151.
Clampitt, P. T.  (1974)  Seasonal migratory cycle and related movements of the freshwater pulmonate snail, Physa integra.  Amer. Midl. Natur. 92: 275-300.
Crowl, T., and A. Covich (1990) Predator-induced life-history shifts in a freshwater snail. Science 247:949-951.
Dawson, J. (1911) The biology of Physa:  in J. B. Watson ed. Behavior Monographs. 1(4):1-120.
David, P., and colleagues (2022) Extreme mitochondrial DNA divergence underlies genetic conflict over sex determination.  Current Biology 32: 2325-2333.  https://doi.org/10.1016/j.cub.2022.04.014.
DeWitt, T. J., A. Sih, & J. Hucko (1999) Trait compensation and cospecialization in a freshwater snail:  size, shape, and antipredator behaviour.  Anim. Behav. 58:397-407. 
DeWitt, T. J., B. W. Robinson, & D. S. Wilson (2000) Functional diversity among predators of a freshwater snail imposes an adaptive trade-off for shell morphology. Evolutionary Ecology Research 2:129-148. 
Dillon, R. T., Jr. (2000) The Ecology of Freshwater Molluscs.  Cambridge University Press, United Kingdom. 509 pp. 
Dillon, R. T., Jr. (2018)  Volatility in the effective size of a freshwater gastropod population.  Ecology and Evolution 8: 2746 - 2751. [PDF]
Dillon, R. T., Jr., and K. Davis (1991) The diatoms ingested by freshwater snails:  Temporal, spatial, and interspecific variation. Hydrobiologia 210:233-242.  
Dillon, R. T., Jr., C. E. Earnhardt & T. P. Smith (2004)  Reproductive isolation between Physa acuta and Physa gyrina in joint culture.  Am. Malac. Bull. 19: 63-68.
Dillon, R. T., Jr. and S. J. Jacquemin (2015)  The heritability of shell morphometrics in the freshwater pulmonate gastropod Physa.  PLoS ONE 10(4) e0121962.  [PDF]
Dillon, R. T., Jr., T. E. McCullough and C. E. Earnhardt (2005a)  Estimates of natural allosperm storage capacity and self-fertilization rate in the hermaphroditic freshwater pulmonate snail, Physa acuta. Invert. Repro. Devel. 47: 111-115.  [PDF]
Dillon, R. T. , Jr., J. D. Robinson, T. P. Smith & A. R. Wethington (2005b) No reproductive isolation between freshwater pulmonate snails Physa virgata and P. acuta. Southwest. Nat. 50: 415 - 422. [PDF]
Dillon, R. T., J. D. Robinson, and A. R. Wethington (2007)  Empirical estimates of reproductive isolation between the freshwater pulmonates Physa acuta, P. pomilia, and P. hendersoni.  Malacologia 49: 283-292.  [PDF]
Dillon, R. T. Jr., and A. R. Wethington (1992) The inheritance of albinism in a freshwater snail, Physa heterostropha. Journal of Heredity 83:208-210. [PDF]
Dillon, R. T., Jr., and A. R. Wethington (1994) Inheritance at five loci in the freshwater snail, Physa heterostropha. Biochem. Genet. 32(3/4): 75-82.  
Dillon, R. T., Jr., and A. R. Wethington (1995) The biogeography of sea islands: clues from the population genetics of the freshwater snail, Physa heterostropha. Syst. Biol. 44: 400-408.  [PDF]
Dillon, R. T., and A. R. Wethington (2006)  The Michigan Physidae revisited: A population genetic study.  Malacologia 48: 133 - 142. [PDF]
Dillon, R. T., A. R. Wethington, and C. Lydeard (2011)  The evolution of reproductive isolation in a simultaneous hermaphrodite, the freshwater snail Physa.  BMC Evolutionary Biology 11:144. [PDF] [html]  
Dillon, R. T., Jr., A. R. Wethington, J. M. Rhett, and T. P. Smith (2002) Populations of the European freshwater pulmonate Physa acuta are not reproductively isolated from American Physa heterostropha or Physa integra.  Invert. Biol. 121(3):226-234. [PDF]
Dorn, N.J. (2013) Consumptive effects of crayfish limit snail populations.  Freshwater Science 32: 1298-1308.
Ebbs, E. T., E. S. Loker and S. V. Brant (2018)  Phylogeny and genetics of the globally invasive snail Physa acuta Draparnaud 1805, and its potential to serve as an intermediate host to larval digenetic trematodes.  BMC Evolutionary Biology 18: 103.
Gustafson, K. D., B. Kensinger, M. Bolek, and B. Luttbeg (2014) Distinct snail (Physa) morphotypes from different habitats converge in shell shape and size under common garden conditions. Evolutionary Ecology Research 16: 77–89.
Janicke, T., P. David, and E. Chapuis (2015)  Environment-dependent sexual selection: Bateman's parameters under varying levels of food availability.  American Naturalist 185: 756-768.
Janicke, T., N. Vellnow, T. Lamy, E. Chapuis, and P. David (2014)  Inbreeding depression of mating behavior and its reproductive consequesnces in a freshwater snail. Behavioral Ecology 25: 288 - 299.
Janicke, T., N. Vellnow, V. Sarda and P. David (2013)  Sex-specific inbreeding depresssion depends on the strength of male-male competition.  Evolution 67: 2861-2875.
Jarne, P., M-A Perdieu, A-F Pernot, B. Delay, and P. David (2000)  The influence of self-fertilization and grouping on fitness attributes in the freshwater snail Physa acuta: population and individual inbreeding depression. J. Evol. Biol. 13:645-655. 
Justice, J.R., and R.J. Bernot.  2014.  Nanosilver inhibits freshwater gastropod (Physa acuta) ability to assess predation risk.  American Midland Naturalist  171(2):340-349.
Kesler, D. H., E. H. Jokinen, and W. R. Mumms (1986) Trophic preferences and feeding morphology of two pulmonate snails species from a small New England pond, U.S.A. Can. J. Zool. 64:2570-2575. 
Martinez, M.A., and D.L. Rogowski.  2011.  Use and apparent partitioning of habitat by an imperiled springsnail (Hydrobiidae) and a cosmopolitan pond snail (Physidae).  Southwestern Naturalist  56(2):216-223.
McCarthy, T., and W. Fisher (2000) Multiple predator-avoidance behaviours of the freshwater snail Physella heterostropha pomilia: responses vary with risk. Freshw. Biol. 44:387-397. 
Stoll, S., D. Früh, B. Westerwald, N. Hormel, and P. Haase.  2013.  Density-dependent relationship between Chaetogaster limnaei limnaei (Oligochaeta) and the freshwater snail Physa acuta (Pulmonata).  Freshwater Science  32(2):642-649.
Te, G. A. (1975)  Michigan Physidae, with systematic notes on Physella and Physodon (Basommatophora:  Pulmonata). Malacological Review 8(1-2):7-30. 
Te, G. A. (1978) The systematics of the family Physidae (Basommatophora:  Pulmonata). Ph.D. Dissertation, University of Michigan, pp. 325. 
Te, G. A. (1980) New classification for the family Physidae (Pulmonata:  Basommatophora). Arch. Moll. 110:179-184.
Turner, A. M. & S. L. Montgomery.  2009.
 Hydroperiod, predators and the distribution of physid snails across the freshwater habitat gradient.  Freshwater Biology 54: 1189-1201.
Wethington, A. R. (2004a) Phylogeny, taxonomy, and evolution of reproductive isolation in Physa (Pulmonata: Physidae)  Ph.D. dissertation, University of Alabama, Tuscaloosa.
Wethington, A. R. (2004b)  Family Physidae. A supplement to the workbook accompanying the FMCS Freshwater Identification Workshop, University of Alabama, Tuscaloosa. 24 pp. [PDF]
Wethington, A. R. and R. T. Dillon, Jr. (1991)
  Sperm storage and evidence for multiple insemination in a natural population of the freshwater snail, Physa. Am. Malac. Bull. 9:99-102.
Wethington, A. R. and R. T. Dillon, Jr. (1993)
Reproductive development in the hermaphroditic freshwater snail, Physa, monitored with complementing albino lines. Proc. Royal Soc. Lond. B 252:109-114. [PDF]
Wethington, A. R. and R. T. Dillon, Jr. (1996) Gender choice and gender conflict in a non-reciprocally mating simultaneous hermaphrodite, the freshwater snail, Physa.  Anim. Behav. 51:1107-1118. [PDF]
Wethington, A. R. and R. T. Dillon, Jr. (1997)  Selfing, outcrossing, and mixed mating in the freshwater snail Physa heterostropha:  lifetime fitness and inbreeding depression. Invert. Biol. 116(3):192-199.   [PDF]
Wethington, A.R. E.R. Eastman, & R. T. Dillon, Jr. (2000)  No premating reproductive isolation among populations of a simultaneous hermaphrodite, the freshwater snail Physa. In: Freshwater Mollusk Symposia Proceedings. Tankersley, RA, Warmolts DI, Watters GT, Armitage BJ, Johnson PD & Butler RS, eds. pp. 245 – 251. Ohio Biological Survey, Columbus.   
Wethington, A. R. & C. Lydeard (2007)  A molecular phylogeny of Physidae (Gastropoda: Basommatophora) based on mitochondrial DNA sequences.  J. Molluscan Stud. 73: 241 - 257. [PDF].
Wethington, A. R., J.M. Rhett, and R.T. Dillon, Jr. (2022) Allozyme, 16S, and CO1 sequence divergence among populations of the cosmopolitan freshwater snail, Physa acuta.  FWGNA Circular 5: 1 - 36 [pdf].
Wethington, A.R., J. Wise & R. T. Dillon, Jr. (2009)  Genetic and morphological characterization of the Physidae of South Carolina, with description of a new species.  Nautilus 123: 282-292.  [PDF]
Young, M.K., R. Smith, K.L. Pilgrim & M.K. Schwartz (2021) Molecular species delimitation refines the taxonomy of native and nonnative physinine snails in North America.  Scientific Reports 11: 21739.  https://doi.org/10.1038/s41598-021-01197-3