Bithynia tentaculata (Linnaeus, 1758)

Common Name: Mud bithynia, faucet snail

Synonyms and Other Names:

faucet snail, bithynia, Bulimus tentaculatus

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Identification: The faucet snail has a shiny pale brown shell, oval in shape, with a relatively large and rounded spire consisting of 5–6 somewhat flattened whorls, no umbilicus, and a very thick lip (Clarke 1981; Jokinen 1992; Mackie et al. 1980). The aperture is less than half the height of the shell (Clarke 1981). Adult B. tentaculata possess a white, calcareous, tear-drop to oval-shaped operculum with distinct concentric rings (Clarke 1981; Jokinen 1992; Pennak 1989). The operculum of juveniles, however, is spirally marked (Jokinen 1992). The operculum is always located very close to the aperture of the shell (Jokinen 1992). The animal itself has pointed, long tentacles and a simple foot with the right cervical lobe acting as a channel for water (Jokinen 1992).

Size: shell is usually no larger than 12–15 mm; the snail is sexually mature by the time it reaches 8 mm in size (Jokinen 1992; Mackie et al. 1980; Peckarsky et al. 1993; Pennak 1989)

Native Range: Europe, from Scandinavia to Greece.

Great Lakes Nonindigenous Occurrences: Bithynia tentaculata was first recorded in Lake Michigan in 1871, but was probably introduced in 1870 (Mills et al. 1993). It spread to Lake Ontario by 1879, the Hudson River by 1892, and other tributaries and water bodies in the Finger Lakes region during the 20th century (Jokinen 1992; Mills et al. 1993). It was introduced to Lake Erie sometime before 1930 (Carr and Hiltunen 1965; Krieger 1985). This snail’s range now extends from Quebec and Wisconsin to Pennsylvania and New York (Jokinen 1992). It has been recorded from Lake Huron, but only a few individuals were found in benthic samples from Saginaw Bay in the 1980s and 1990s (Nalepa et al. 2002).

Table 1. Great Lakes region nonindigenous occurrences, the earliest and latest observations in each state/province, 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 Bithynia tentaculata are found here.

Full list of USGS occurrences

State/ProvinceYear of earliest observationYear of last observationTotal HUCs with observations†HUCs with observations†
Illinois187119741Lake Michigan
Michigan1891201622Au Gres-Rifle; Black-Macatawa; Brevoort-Millecoquins; Carp-Pine; Detroit; Kalamazoo; Kawkawlin-Pine; Keweenaw Peninsula; Lake Erie; Lake Huron; Lake Michigan; Lone Lake-Ocqueoc; Manistee; Muskegon; Ottawa-Stony; Pere Marquette-White; Pigeon-Wiscoggin; Saginaw; St. Clair; St. Marys; Sturgeon; Tacoosh-Whitefish
Minnesota200620161St. Louis
New York1879201512Great Lakes Region; Irondequoit-Ninemile; Lake Ontario; Lower Genesee; Mettawee River; Niagara; Oak Orchard-Twelvemile; Oneida; Oswego; Richelieu River; Salmon-Sandy; Seneca
Ohio188820125Ashtabula-Chagrin; Cedar-Portage; Lake Erie; Ottawa-Stony; Sandusky
Pennsylvania191120142Chautauqua-Conneaut; Lake Erie
Vermont188219742Lake Champlain; Richelieu River
Wisconsin1974201710Duck-Pensaukee; Lake Michigan; Lake Superior; Lake Winnebago; Lower Fox; Milwaukee; Peshtigo; St. Louis; Upper Fox; Wolf

Table last updated 9/30/2019

† Populations may not be currently present.

* HUCs are not listed for areas where the observation(s) cannot be approximated to a HUC (e.g. state centroids or Canadian provinces).

Ecology: Commonly found in freshwater ponds, shallow lakes, and canals. This species is found on the substrate in fall and winter (including gravel, sand, clay, mud or undersides of rocks) and on aquatic macrophytes (including milfoil, Myriophyllum spicatum and muskgrass, Chara spp.) in warmer months (Jokinen 1992; Pennak 1989; Vincent et al. 1981). It lives mostly in shoals, but is found at depths up to 5 m (Jokinen 1992). This species can inhabit intertidal zones in the Hudson River (Jokinen 1992). In general, the faucet snail inhabits waters with pH of 6.6–8.4, conductivity of 87–2320 μmhos/cm, Ca++ of 5–89 ppm, and Na+ of 4–291 ppm (Jokinen 1992). It can potentially survive well in water bodies with high concentrations of K+ and low concentrations of NO3- (Jokinen 1992). In the St. Lawrence River, it tends to occur in relatively unpolluted, nearshore areas (Vaillancourt and Laferriere 1983) and amongst dreissenid mussel beds (Ricciardi et al. 1997).

This species functions as both a scraper and a collector-filterer, grazing on algae on the substrate, as well as using its gills to filter suspended algae from the water column. When filter feeding, algae is sucked in, condensed, and then passed out between the right tentacle and exhalant siphon in pellet-like packages which are then eaten (Jokinen 1992). The ability to filter feed may play a role in allowing populations of the faucet snail to survive at high densities in relatively eutrophic, anthropogenically influenced water bodies (Jokinen 1992). Faucet snails feeds selectively on food items (Brendelberger 1997). The faucet snail is known in Eurasia to feed on black fly larvae (Pavlichenko 1977).

Bithynia tentaculata is dioecious and lays its eggs on rocks, wood and shells in organized aggregates arranged in double rows, in clumps of 1–77. Egg-laying occurs from May to July when water temperature is 20ºC or higher, and sometimes a second time in October and November by females born early in the year. The density of eggs on the substrate can sometimes reach 155 clumps/m2.  Fecundity may reach up to 347 eggs and is greatest for the 2nd year class. Eggs hatch in three weeks to three months, depending on water temperature. Oocytes develop poorly at temperatures of 30–34ºC. Growth usually does not occur from September to May.  The lifespan varies regionally and can be anywhere from 17 – 39 months (Jokinen 1992; Korotneva and Dregol’skaya 1992).

In its native Eurasian habitat, the faucet snail is host to many different species of digeneans, cercariae, metacercariae, cysticercoids, and other parasites (Mattison et al. 1995; Morley et al. 2004; Toledo et al. 1998). Natural dispersal of this snail is known to occur by passive transport in birds (von Proschwitz 1997). Bithynia tentaculata is capable of detecting the presence of molluscivorous leeches through chemoreception and of closing its operculum to avoid predation (Kelly and Cory 1987).

The faucet snail has the potential to be a good biomonitor for contaminants such as Cd, Zn, and MeHg because there are good correlations between environmental concentrations and snail tissue concentrations with respect to these toxic compounds (Desy et al. 2000; Flessas et al. 2000).

Means of Introduction: Bithynia tentaculata could have been introduced to the Great Lakes basin in packaging material for crockery, through solid ballast in timber ships arriving to Lake Michigan, or by deliberate release by amateur naturalists into the Erie Canal, Mohawk River and Schuyler’s Lake (Mills et al. 1993). The most likely and most accepted explanation for its original introduction is the solid ballast vector (Jokinen 1992). Populations outside of the Great Lakes are likely the result of the Great Lakes introduction rather than separate introductions (Perez et al. 2016)

Status: The species is established in the drainages of Lake Ontario (Mills et al. 1993; Peckarsky et al. 1993), Lake Michigan (Mills et al. 1993), and Lake Erie (Krieger 1985; Mackie et al. 1980; Peckarsky et al. 1993), but not Lake Superior (Jokinen 1992). Occurrences in Lake Huron do not warrant classification as established.

Great Lakes Impacts:  

Bithynia tentaculata has a high environmental impact in the Great Lakes.

Between 1917 and 1968, the species richness of mollusks in Oneida Lake, NY declined by 15% as the faucet snail increased in abundance (Harman 2000). It is very probable that the faucet snail has particularly impacted pleurocerids, as seen with Elimia spp. in Oneida Lake, due to its higher growth rates (Tashiro and Colman 1982). However, after invasive zebra mussels (Dreissena polymorpha) colonized Oneida Lake, the density of faucet snails decreased and overall mollusk diversity diminished even further (Harman 2000). Similar effects occurred in Lake Ontario between 1983 and 2000 due to competition with invasive dreissenid mussels (Haynes et al. 2005).

After the introduction of B. tentaculata into the Erie Canal, the faucet snail began replacing two pleurocerid species, Elimia virginica and E. livescens (Jokinen 1992). Where the faucet snail has been observed in Lake Champlain, NY, it generally dominates gastropod assemblages (Vermont and New York State Departments of Environmental Conservation 2000).

In its native Eurasian habitat, the faucet snail is host to many different species of digeneans, cercariae, metacercariae, cysticercoids, and other parasites, some of which also parasitize fish and other wildlife (Mattison et al. 1995, Morley et al. 2004, Toledo et al. 1998). Bythinia tentaculata is known to be an intermediate host of three species of trematodes—Cyathocotyle bushiensis, Sphaeridiotrema globulus, and Leyogonimus polyoon—which can lethally parasitize birds when the snail is eaten (Herrmann and Sorensen 2009, Mitchell and Cole 2008, Sauer et al. 2007). The introduction of B. tentaculata has been linked to extensive mortality of migratory waterbirds in the Upper Mississippi River National Wildlife and Fish Refuge in Wisconsin due to its role as a host of C. bushiensis and S. globules (Herrmann and Sorensen 2009, Sauer et al. 2007). Between 2002 and 2006, over 20,000 migratory birds died at this location due to these parasites. Duck (Anas spp.) mortality in lower Quebec was credited to these two trematodes and their snail host (Ménard and Scott 1987), as was the death of 6,000-7,000 scaup (Aythya spp.) over a two month period at Lake Winnibigoshish in 2007 (Lawrence et al. 2009). A 1997 mass mortality event of over 10,000 water birds (particularly American coot, Fulica americana, and lesser scaup, Aythya affinis) was also reported at Shawano Lake, WI (Cole 2001, Cole and Franson 2006). Bythinia tentaculata occurs in this WI lake, and the deaths were primarily attributed to the presence of L. polyoon, the third trematode species hosted by B. tentaculata (Cole 2001, Cole and Franson 2006).

Laboratory research on the impact of grazing by B. tentaculata indicated that it can have complex impacts on the periphyton community (Burgmer et al. 2010). Through direct and indirect effects, B. tentaculata grazing contributed to a shift from larger filamentous algae to small prostrate forms, was associated with a significant reduction in the biomass of heterotrophic nanoflagellates and ciliates, and was also linked to a weak decline in meiofauna biomass (Burgmer et al. 2010). Grazing by B. tentaculata, along with another snail species, was correlated with a decline in microalgal species richness (but increased evenness) and a significant reduction in the biomass microalgae, nanoautrophs, and bacteria (Burgmer et al. 2010).

Bythinia tentaculata often interacts with other nonindigenous species. It can serve as a food item for nonindigenous common carp, Cyprinus carpio (Ricciardi 2001), and is frequently found on introduced milfoil, Myriophyllum spicatum (Vincent et al. 1981), and among introduced dreissenid mussels (Ricciardi et al. 1997).

Bithynia tentaculata has a moderate socio-economic impact in the Great Lakes.

Historically, this species has been known to infest municipal water supplies in abundance (Mills et al. 1993). The snail also has the potential to be a bio-fouling organism in underwater intakes and in swimming areas (Vermont and New York State Departments of Environmental Conservation 2000).

In areas of Wisconsin where the trematode parasites of B. tentaculata are causing large die-offs of waterbirds (see Environmental Impact above), these mass mortalities have fueled health concerns among waterfowl hunters and increased the difficulty of hunting game (Sauer et al. 2007). These mass mortality events have also resulted in restricted recreational access during periods of cleanup (Cole 2001, Lawrence et al. 2009, Sauer et al. 2007).

There is little or no evidence to support that Bithynia tentaculata has significant beneficial effects in the Great Lakes.

The faucet snail has the potential to be a good biomonitor for contaminants such as cadmium, zinc, and methylmercury, owing to well-known correlations between environmental concentrations and snail tissue concentrations of these toxic compounds (Desy et al. 2000, Flessas et al. 2000).


Regulations (pertaining to the Great Lakes region)
Faucet snails are listed as prohibited species in New York, Wisconsin, and Minnesotta.

Note: Check federal, state/provincial, and local regulations for the most up-to-date information.

There are currently no documented successful methods for the control of faucet snails in open water ecosystems. 

There are no known biological control methods for this species.

In an attempt to limit the number of faucet snails in the Upper Mississippi River National Wildlife and Fish Refuge, biologists experimented with covering colonies of faucet snails with sand (Williams 2007). The success of this method was undocumented.

There are no known chemical control methods for this species.

Note: Check state/provincial and local regulations for the most up-to-date information regarding permits for control methods. Follow all label instructions.

Remarks: Bithynia was found in fossils from the Pleistocene in Glacial Lake Chicago (Jokinen 1992), but the only representative of the genus currently found in the Great Lakes is Eurasian. Bithynia tentaculata is synonymous with Bulimus tentaculatus (Jokinen 1992).

References: (click for full references)

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

Contributing Agencies:

Revision Date: 9/25/2019

Citation for this information:
Kipp, R.M., A.J. Benson, J. Larson, and A. Fusaro, 2020, Bithynia tentaculata (Linnaeus, 1758): U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, and NOAA Great Lakes Aquatic Nonindigenous Species Information System, Ann Arbor, MI,, Revision Date: 9/25/2019, Access Date: 2/27/2020

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.