FWGNA > Species Accounts > Lymnaeidae > Lymnaea humilis
Lymnaea (Galba) humilis Say 1822
"Fossaria humilis"
  • click to view larger

> Habitat & Distribution

Lymnaea humilis ranges throughout North America, from Alaska to Florida (Baker 1911, Clarke 1981, Jokinen 1992, Thompson 1999).  Populations are frequently semiaquatic, inhabiting muddy areas at or above the water line near streams, lakes, ponds, and marshes (Clarke 1981, Stewart and Dillon 2004). Lymnaea humilis can inhabit oligotrophic, mesotrophic, or eutrophic water bodies (Clarke 1979) and is an excellent colonizer of new habitats, quickly invading young ponds devoid of vegetation and other species of gastropods (Jokinen 2005).

Populations of L. humilis are widespread throughout drainages of The Ohio and Middle Atlantic states, becoming less common further south.  For quite a few years we were unable to locate any populations in South Carolina whatsoever, especially puzzling in view of the fact that the type locality of L. humilis was given as "South Carolina" by Say (1822).  See my essay of 25June08 (link below) for further discussion.  More recently we have discovered scattered populations along the Wateree and Congaree Rivers in Kershaw and Richland Counties.  We also have one record from Georgia, by the Yellow River at Porterdale.  FWGNA incidence rank I-5.

> Ecology & Life History

Although L. humilis can thrive in waters with low levels of dissolved oxygen, populations in Manitoba disappeared from several sites affected by intensive agriculture and logging (Pip 2000). Flooding from hydro dams has also caused local extinctions of semiaquatic L. humilis populations in Manitoba.

Like other pulmonate snails, L. humilis is monecious and almost certainly capable of self-fertilization as well as outcrossing (Dillon 2000).  Populations of the (closely related) L. truncatula of Europe seem to reproduce primarily by selfing (Trouve' et al. 2003).  Lymnaeid egg masses are gelatinous, transparent, and sausage-shaped (Clarke 1981).  Studies of population size frequency distribution have suggested an annual life cycle for L. humilis (Type A of Dillon 2000: 156 - 162), with a maximum lifespan of 16 months (McKillop 1985, Jokinen 1992). Brown (2001) suggested that L. humilis may lay eggs continuously throughout the summer.

Dillon’s (2000: 360-363) USR reanalysis of Jokinen’s Connecticut data suggested that L. humilis populations (listed as Fossaria modicella Say, 1825) seem to be Undifferentiated with respect to life history adaptation.

Lymnaea humilis is one of many amphibious lymnaeid taxa capable of serving as an intermediate host for trematodes causing fascioliasis in livestock, and rarely humans (Remigio 2002, Mas-Coma et al. 2005).

> Taxonomy & Systematics

The taxonomy of L. humilis has become elaborately entangled with that of L. cubensis, a similarly small, amphibious species more southern in its distribution.  Baker (1911) was the first to distinguish the two species by the number of cusps on their first marginal tooth, humilis with three and cubensis with two.  It seems likely, however, that the specimens in Thomas Say’s hand when he described humilis in 1822 were not tricuspid, but rather from a bicuspid population collected near Charleston, South Carolina.  For that reason, we recommend that the type locality for L. humilis be restricted to the Susquehanna River at Owego, NY, where populations are entirely tricuspid.  See my essay of 25June08 from the link below.

Quite a few molecular phylogenies have been published in recent years involving L. humilis, L. cubensis, and similar populations worldwide (e.g., Correa et al. 2010, 2011).  See my post to the FWGNA blog of 7Aug12 from the link below for a critical examination of this literature.

Baker’s original (1911) classification of the Lymnaeidae assigned humilis (together with at least 60 – 80 other specific nomina) to a large, inclusive genus Galba (Schrank 1803), which he later (1928) subdivided and emended to Fossaria (Westerlund 1885).  Burch (1989) followed Baker (1928), gathering humilis together with ten other nominal species and subspecies of small, amphibious lymnaeids into the subgenus Fossaria (s.s.).  Meanwhile, European consensus has continued to favor Galba.

Modern molecular data seem to confirm Hubendick’s (1951) impressions that essentially all ten of our North American "fossarine" taxa are conspecific, however, as indeed are most of the nominal species assigned to "Galba" worldwide.  Thus we continue to prefer the two-genus system of Hubendick, with Galba at most a subgenus.  See the essay of 28Dec06 available from the link below for more.

Among the many junior synonyms of L. humilis listed by Hubendick (1951) were: cyclostoma, dalli, exigua, galbana, modicella, obrussa, parva, peninsulae, rustica, and tazewelliana.

> Supplementary Resources [pdf]

> Essays

> References

Baker, F. C. 1911.  The Lymnaeidae of North and Middle America, Recent and Fossil. Special Publication, no. 3.  Chicago: Chicago Academy of Natural Sciences.  539 pp, 55 pl.
Baker, F. C. 1928.
Freshwater Mollusca of Wisconsin, Part I, Gastropoda. Bull. Wisc. Geol. Natur. Hist. Survey, no. 70. Madison: University of Wisconsin Press.
Brown, K.M. 1982.
Resource overlap and competition in pond snails: an experimental analysis. Ecology 63:412-422. 
Brown, K.M. 2001. Mollusca: Gastropoda. In: J.H. Thorp and A.P. Covich, eds., Ecology and Classification of North American Freshwater Invertebrates, Academic Press, New York. Pp. 297-329.
Burch, J. B. 1989.  North American Freshwater Snails.  Malacological Publications, Hamburg, MI.  365 pp.
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.
Correa, A. C., J. S. Escobar, P. Durand, F. Renaud, P. David, P. Jarne, J-P Pointier, & S. Hurtrez-Bousses.  2010.  Bridging gaps in the molecular phylogeny of the Lymnaeidae (Gastropoda: Pulmonata), vectors of Fascioliasis.  BMC Evolutionary Biology 10: 381.
Correa, A. C., J. S. Escobar, O. Noya, L. E. Velasquez, C. Gonzalez-Ramirez, S. Hurtrez-Bousses, and J. P. Pointier.  2011.  Morphological and molecular characterization of Neotropic Lymnaeidae (Gastropoda: Lymnaeoidea), vectors of fasciolosis.  Infection, Genetics and Evolution  11: 1978-1988.
Dillon, R.T., Jr. 2000.  The Ecology of Freshwater Molluscs.  Cambridge University Press, Cambridge, United Kingdom.
Hoff, C. C.  1936.  Studies on the lymnaeid snail, Fossaria parva (Lea).  Part I.  Winter habits. Trans.  Illinois Acad. Sci. 29: 29: 259 - 262.
Hoff, C. C.  1936.  Studies on the lymnaeid snail, Fossaria parva (Lea).  Part II.  Seasonal life history.  Trans. Illinois Acad. Sci. 30: 303 - 306. 
Hubendick, B. 1951.  Recent Lymnaeidae. Their variation, morphology, taxonomy, nomenclature, and distribution. Kungl. Svenska Vetensk. Akad. Handl., 3, 1-223. 
Jokinen, E. 1983. The freshwater snails of Connecticut.  State Department of Environmental Protection Bulletin 109, 83 pp.
Jokinen, E.H. 1992.  The Freshwater Snails (Mollusca: Gastropoda) of New York State. NY State Mus Bull 482, Albany, New York. 
Jokinen, E.H. 2005.  Pond molluscs of Indiana Dunes National Lakeshore: then and now. Amer Malac Bull 20:1-9.  
Mas-Coma, S., M. D. Bargues, & M. A. Valero  2005.  Fascioliasis and other plant-borne trematode zoonoses.  Int. J. Parasit. 35: 1255-1278.  
McKillop, W.B. 1985.  Distribution of aquatic gastropods across the Ordovician dolomite – Precambrian granite contact in southeastern Manitoba, Canada. Can J Zool 63:278-288. 
Pip, E. 2000.  The decline of freshwater molluscs in southern Manitoba. Can Field-Nat 114:555-560.   
Remigio, E. A.  2002.  Molecular phylogenetic relationships in the aquatic snail genus Lymnaea, the intermediate host of the causative agent of fascioliasis: insights from broader taxon sampling.  Parasitology Reserach 88: 687-696.  
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. Amer Malac Bull 19:79-91.
Trouve', S., L. Degen, F. Renaud & J. Goudet.  2003.  Evolutionary implications of a high selfing rate in the freshwater snail Lymnaea truncatula.  Evolution 57: 2303-2314.
Thompson, F.  1999. An identification manual for the freshwater snails of Florida.  Walkerana 10: 1 - 96.
van Cleave, H. J. 1935.  The seasonal life history of an amphibious snail, Fossaria modicella, living on sandstone cliffs.  Ecology 16: 101-108.