The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

Radix auricularia
Radix auricularia
(European ear snail)

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Radix auricularia (Linnaeus, 1758)

Common name: European ear snail

Synonyms and Other Names: Lymnaea auricularia

Taxonomy: available through www.itis.govITIS logo

Identification: Radix auricularia has a width to length ratio greater than 0.75.  The ear-shaped aperture, which contains no operculum, is around 5 times higher than the spire (Jokinen 1992, Mackie et al. 1980, Peckarsky et al. 1993). The shell is thin and very inflated such that the last whorl comprises 90% of its volume (Clarke 1981, Jokinen 1992, Peckarsky et al. 1993). The umbilicus is either wide or covered, the shell has a rounded and broad spire that pinches in steeply at the apex, and there are 4–5 whorls with deep sutures between them (Clarke 1981, Jokinen 1992).  The color of the shell is yellow, beige or tan.  The mantle is pigmented with a line of dark spots along its edge (Falniowski 1980).  This species also has tentacles that are lobate, fan-shaped and wider than they are high (Jackiewicz and Buksalewicz 1998). The blood contains blue hemocyanin (Jing 1983). This species can grow to ~30 mm in height (Jokinen 1992) and 25 mm in width (Clarke 1981) as a full grown adult. However, most individuals in a population only grow to approximately half the maximum size (Clarke 1981).

Size: can reach 35 mm in height

Native Range: Radix auricularia is native to Europe and Asia (Jokinen 1992).

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Nonindigenous Occurrences:

Table 1. States with nonindigenous occurrences, the earliest and latest observations in each state, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Radix auricularia are found here.

StateFirst ObservedLast ObservedTotal HUCs with observations†HUCs with observations†
AK201620222Healy Lake-Tanana River; Upper Kenai Peninsula
AZ197419741Upper Santa Cruz
CA1946202228Battle Creek; Big-Navarro-Garcia; California Region; Crowley Lake; East Branch North Fork Feather; Honcut Headwaters-Lower Feather; Honey-Eagle Lakes; Los Angeles; Lower Eel; Lower Klamath; Lower Pit; Lower San Joaquin River; Middle Fork Feather; North Fork Feather; Russian; San Francisco Bay; San Francisco Coastal South; San Joaquin; Scott; Shasta; South Fork Eel; Tomales-Drake Bays; Trinity; Upper Cache; Upper Pit; Upper Putah; Upper Yuba; Ventura-San Gabriel Coastal
CO1912198914Alamosa-Trinchera; Cache La Poudre; Fountain; Huerfano; Mancos; Middle San Juan; North Platte Headwaters; Piedra; South Platte Headwaters; St. Vrain; Uncompahgre; Upper Arkansas-Lake Meredith; Upper San Juan; Upper South Platte
CT197619761Quinebaug River
ID193120229Bruneau; Clearwater; Lake Walcott; Lower Kootenai; Middle Snake-Succor; Palouse; Pend Oreille Lake; St. Joe; Upper Snake-Rock
KS202120211Middle Kansas
KY196919691Lower Kentucky
MA191219953Charles; Gulf of Maine/Bay of Fundy; Hudson-Hoosic
MI197419742Detroit; Lake Huron
NV197920173Havasu-Mohave Lakes; Spring-Steptoe Valleys; Truckee
NM196620217Cimarron; Mimbres; Mora; Rio Grande-Santa Fe; San Francisco; Upper Gila; Upper Rio Grande
NY186919976Hudson-Hoosic; Lake Ontario; Lower Hudson; Middle Hudson; Seneca; Southern Long Island
OH191119741Lake Erie
OR2008202218Donner und Blitzen; Goose Lake; Little Deschutes; Lost; Lower Willamette; Middle Fork John Day; Middle Fork Willamette; North Fork John Day; North Umpqua; Powder; Silver; South Umpqua; Sprague; Summer Lake; Upper Crooked; Upper Deschutes; Upper Klamath; Upper Malheur
PA191219743Lehigh; Lower Delaware; Lower Susquehanna
UT2018202111East Fork Sevier; Little Bear-Logan; Lower Bear-Malad; Lower Green-Diamond; Price; Provo; San Pitch; Spanish Fork; Strawberry; Upper Sevier; Utah Lake
VT197420002Hudson-Hoosic; Lake Champlain
WA196820216Chief Joseph; Deschutes; Lower Yakima; Middle Columbia-Hood; Rock; Upper Columbia-Entiat
WI200620061Lake Superior
WY198820153Missouri Region; Snake Headwaters; Upper Laramie

Table last updated 6/19/2024

† Populations may not be currently present.

Ecology: Found in freshwater lakes, ponds, and slow-moving rivers with mud bottoms. Radix auricularia can live on boulders or vegetation in low or high flow environments and is capable of tolerating anoxic conditions, but tends to prefer very lentic waters in lakes, bogs or slow rivers where there is a silt substrate (Clarke 1981, Jokinen 1992, Systsma et al. 2004).  It has been found in environments with pH from 6.0–7.1 (Jokinen 1992, Maqbool et al. 1998). Its average thermal preference is ~19ºC, but there is great fluctuation around this mean depending on the photoperiod for the time of year (Rossetti et al. 1989). In Great Britain, the species is restricted to hard water (Adam and Lewis 1992). It can tolerate polysaprobic waters, or areas of major pollution and anoxia with high concentrations of organic matter, sulphides and bacteria (Goodnight 1973, Matuskova 1985).            

Radix auricularia is in the family Lymnaeidae, which consists of scrapers and collector-gatherers.  This species feeds on such items as detritus, Cladophora spp. (algae), and sand grains (Adam and Lewis 1992). 

It is a hermaphrodite, undergoing oogenesis in spring as daylight hours increase and spermatogenesis in late summer and early fall as daylight hours decrease (Berezkina 1981). It is iteroparous, breeding biennially (Adam and Lewis 1992). Eggs develop faster as temperature increases from 10ºC upward but fail to survive and develop at 36ºC (Salish et al. 1981).

Means of Introduction: This snail was most likely first introduced in the late 1800s accidentally on plants that were imported to North American greenhouses.  Subsequent introductions may have occurred through releases from aquaria (Mills et al. 1993).  Considering its patchy distribution, it is likely that this species has been introduced multiple times (Mills et al. 1993).

Status: Mackie et al. (1980) consider this species rare in the Great Lakes.  Nevertheless, it has apparently established local populations in the Lake Ontario drainage, the Lake Erie drainage, the Lake Michigan drainage, and Lake Huron (Dundee 1974, Mills et al. 1993).

Impact of Introduction:

A) Realized: There are no known impacts associated with the introduction of R. auricularia to the Great Lakes basin.  

B) Potential: This species has shown a potential to adapt to new environments within large lakes, as indicated by its recent history in Lake Baikal, Russia, where this introduced species was previously restricted to shallow bays and floodplain areas, but has recently been able to colonize the rocky drop-off in the lake (Stift et al. 2004). The shells of those snails in the new habitat have a more inflated aperture and are more compact than those in the shallow zones, indicating that wave action may have selected for snails with a stronger suctioning foot in the newly colonized habitat (Stift et al. 2004).            
Various limnaeid snails, including R. auricularia, are vectors for a diverse range of parasites, particularly trematodes (Boray 1978).  In Europe and Asia R. auricularia is a host in Europe and Asia to such parasites including Echinoparyphium recurvatum (Sohn et al. 2002), Trichobilharzia franki (Ferte et al. 2005), T. ocellata (Zbikowska 2004), T. szidati (Kolarova et al. 1997), Clinostomum complanatum (Chung et al. 1998), Mantoscyphidia radixi (Boshko 1993), Orientobilharzia turkestanica (Tang et al. 1990), some of which may infect humans.  One study found that average shell height and infection severity with Trichobilharzia spp. are positively related (Allgoewer 1990).

In its native habitat, this species preys on eggs of the parasite Ascaris suum, which survive and develop after passage through the gut, and are dispersed widely due to activity of the snail (Asitinskaya 1975).

References: (click for full references)

Adam, M.E., and J.W. Lewis. 1992. The lack of co-existence between Lymnaea peregra and Lymnaea auricularia (Gastropoda: Pulmonata). Journal of Molluscan Studies 58(2):227-228.

Allgoewer, R. 1990. The trematode fauna of several Freiburg dredging pools with special regard to the pathogen of cercarial dermatitis in humans. Mitteilungen des Badischen Landesvereins fuer Naturkunde und Naturschutz E V Freiburg im Breisgau 15(1):59-80.

Asitinskaya, S.E. 1975. The role of mollusks as benthos components in purification of water bodies from Ascaris suum eggs. Paraziologiya 9(5):432-433.

Berezkina, G.V. 1981. Seasonal changes in reproductive system of the Lymnaeidae. Zoologicheskii Zhurnal 60(7):978-983.

Boray, J.C. 1978. The potential impact of exotic Lymnaea spp. on fascioliasis in Australia. Veterinary Parasitology 4(2):127-142.

Boshko, E.G. 1993. New species of ciliphoran infusoria genus Mantoscyphidia (Peritricha) from fresh water mollusks. Vestnik Zoologii 0(6):14-19.

Chung, D.-I., H.-H. Kong, and C.-Y. Joo. 1998. Radix auricularia coreana: natural snail host of Clinostomum complanatum in Korea. Korean Journal of Parasitology 36(1):1-6.

Clarke, A.H. 1981.  The freshwater molluscs of Canada.  National Museum of Natural Sciences, National Museums of Canada, Ottawa, Canada. 447 pp.

Dundee, D.S. 1974. Catalogue of introduced mollusks of eastern North America (north of Mexico).

Falniowski, A. 1980. Pigmentation of the mantle border in Polish representatives of the subgenus Radix (Lymnaeidae, Basommatophora, Gastropoda). Basteria 44(1-4):3-8.

Ferte, H., J. Depaquit, S. Carre, I. Villena, and N. Leger. 2005. Presence of Trichobilharzia szidati in Lymnaea stagnalis and T-franki in Radix auricularia in northeastern France: molecular evidence. Parasitology Research 95(2):150-154.

Goodnight, C.J. 1973. The use of aquatic macroinvertebrates as indicators of stream pollution. Transactions of the American Microscopical Society 92(1):1-13.

Jackiewicz, M., and R. Buksalewicz. 1998. Diversity in tentacle shape of European lymnaeid species (Gastropoda, Pulmonata: Basommatophora). Biological Bulletin of Poznan 35(2):131-136.

Jing, Z. 1983. Anatomy of the circulatory system of Radix auricularia. Acta Zoologica Sinica 29(2):133-140.

Jokinen, E. 1992. The Freshwater Snails (Mollusca: Gastropoda) of New York State. The University of the State of New York, The State Education Department, The New York State Museum, Albany, New York 12230. 112 pp.

Kolarova, L., P. Horak, and J. Sitko. 1997. Cercarial dermatitis in focus: schistosomes in the Czech Republic. Helminthologia (Bratislava) 34(3):127-139.

Mackie, G.L., D.S. White, and T.W. Zdeba. 1980. A guide to freshwater mollusks of the Laurentian Great Lakes with special emphasis on the genus Pisidium. Environmental Research Laboratory, Office of Research and Development, U. S. Environmental Protection Agency, Duluth, Minnesota 55804. 144 pp.

Majoros, G., A. Dán, K. Erdélyi. 2010. A natural focus of the blood fluke Orientobilharzia turkestanica (Skrjabin, 1913) (Trematoda: Schistosomatidae) in red deer (Cervus elaphus) in Hungary. Veterinary Parasitology 170:218-223.

Maqbool, A., C.S. Hayat, T. Akhtar, A.D. Anjum, and B. Hayat. 1998. Prevalence and ecology of freshwater snails in Punjab. Malaysian Applied Biology 27(1-2):69-72.

Matuskova, M. 1985. The significance of water mollusks in estimating the water pollution stage in the watershed of the Zitava River, Czechoslovakia. Biologia (Bratislava) 40(10):1021-1030.

Mills, E.L., J.H. Leach, J.T. Carlton, and C.L. Secor. 1993. Exotic species in the Great Lakes: a history of biotic crises and anthropogenic introductions. Journal of Great Lakes Research 19(1):1-54.

Peckarsky, B.L., P.R. Fraissinet, M.A. Penton, and D.J. Conklin Jr. 1993. Freshwater Macroinvertebrates of Northeastern North America. Cornell University Press, Ithaca, New York State. 442 pp.

Rossetti, Y., L. Rossetti, and M. Cabanac. 1989. Annual oscillation of preferred temperature in the freshwater snail Lymnaea auricularia; effect of light and temperature. Animal Behaviour 37(6):897-907.

Soldánová, M., C. Selbach, B. Sures, A. Kostadinova, A. Pérez-del-Olmo. 2010. Larval trematode communities in Radix auricularia and Lymnaea stagnalis in a reservoir system of the Ruhr River. Parasites and Vectors 3:56-68.

Salih, T., O. Al-Habbib, W. Al-Habbib, S. Al-Zako, and T. Ali. 1981. The effects of constant and changing temperatures of the development of eggs of the freshwater snail Lymnaea auricularia (L.). Journal of Thermal Biology 6(4):379-388.

Sohn, W.-M., H.-C. Woo, and S.-J. Hong. 2002.Tegumental ultrastructures of Echinoparyphium recurvatum according to developmental stages. Korean Journal of Parasitology 40(2):67-73.

Stift, M., E. Michel, T.Y. Sitnikova, E.Y. Mamonova, and D.Y. Sherbakov. 2004. Palaearctic gastropod gains a foothold in the dominion of endemics: range expansion and morphological change of Lymnaea (Radix) auricularia in Lake Baikal. Hydrobiologia 513(1-3):101-108.

Sytsma, M.D., J.R. Cordell, J.W. Chapman, and R.C. Draheim. 2004. Lower Columbia River Aquatic Nonindigenous Species Survey 2001-2004. Final Technical Report: Appendices. Prepared for the United States Coast Guard and the Unites States Fish and Wildlife Service. 164 pp.

Tang, C., G. Cui, Y. Qian, S. Lu, and H. Lu. 1990. Structural changes in different aged worms of Orientobilharzia turkestanica of sheep in Horqin pasture of inner Mongolia and the hatching periodicity of the Miracidia. Acta Zoologica Sinica 36(4):366-376.

Zbikowska, E. 2004. Infection of snails with bird schistosomes and the threat of swimmer’s itch in selected Polish lakes. Parasitology Research 92(1):30-35.

Other Resources:
Great Lakes Water Life

Author: Kipp, R.M., A.J. Benson, J. Larson, and A. Fusaro

Revision Date: 11/26/2019

Citation Information:
Kipp, R.M., A.J. Benson, J. Larson, and A. Fusaro, 2024, Radix auricularia (Linnaeus, 1758): U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?SpeciesID=1012, Revision Date: 11/26/2019, Access Date: 6/19/2024

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.


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Citation information: U.S. Geological Survey. [2024]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [6/19/2024].

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