Invasion History

First Non-native North American Tidal Record: 1925
First Non-native West Coast Tidal Record: 1938
First Non-native East/Gulf Coast Tidal Record: 1925

General Invasion History:

Cipangopaludina chinensis is native to fresh waters of China. The extent of its range in Asia is not clear, owing to confused taxonomy. The taxonomic distinctness of Heterogen. japonica (Japanese Mystery Snail) has been debated (Clench and Fuller 1965; Jokinen 1982), but the two species are now recognized as distinct (Smith 2000). Cipangopaludina chinensis was first found in North America as a living food item in Chinese markets in San Francisco in 1892. By 1911, they were established in freshwater sites between San Jose and San Francisco, and were collected in the estuarine Sacramento-San Joaquin Delta by 1938 (Cohen and Carlton 1995). This large handsome freshwater snail quickly found its way into the aquarium trade and is frequently kept in aquaria and goldfish ponds. In addition to the pet trade, these snails can be dispersed on boats and trailers, or with the shipment and sale of ornamental aquatic plants. Adults can survive air exposure for up to four weeks, and small juveniles (6-8 mm) can survive for 3-14 days, depending on temperature and humidity (Havel 2011).

Cipangopaludina chinensis has become widespread in scattered locations, mostly ponds, lakes, and reservoirs, but sometimes also colonizing river systems from California to British Columbia and Florida to Maine and Quebec. It has also been found in many locations in the interior of the continent, including the Great Lakes. It is known from tidal fresh waters of several estuaries on the East and West coast, but to our knowledge has not been found in brackish water. Overall, it has been collected in 29 states (Jokinen 1982; USGS Nonindigenous Aquatic Species Program 2010). Populations are probably more numerous than the widely separated records indicate. However, some of the records probably refer to Heterogen japonica (Clench and Fuller 1965; Jokinen 1982; Smith 2000). Cipangopaludina chinensis was also introduced to fresh waters of Hawaii (Cowie 1998), and most recently, to the Netherlands (Soes et al. 2011).

North American Invasion History:

Invasion History on the West Coast:

Cipangopaludina chinensis was first found in North America as a living food item in Chinese markets in San Francisco in 1892. By 1911, they were established in freshwater sites between San Jose and San Francisco, and were collected in the estuarine Sacramento-San Joaquin Delta by 1938 (Cohen and Carlton 1995). Specific records (undated) are from Suisan City and Stockton (Clench and Fuller 1965). Cipangopaludina chinensis is abundant through the freshwaters of the Delta (Cohen and Carlton 1995). In 2009, the Chinese Mystery snail was found to be established in Freshwater Lagoon, a coastal lake in Humboldt County (USGS Nonindigenous Aquatic Species Program 2013). Cipangopaludina chinensis was found in the Columbia River estuary in 2002 (Sytsma et al. 2004). One specific location is from Longview, Washington in the tidal fresh region of the estuary (USGS Nonindigenous Aquatic Species Program 2013). The Chinese Mystery Snail has been reported found from in ponds, reservoirs and rivers in the Pacific drainage from British Columbia through California (Jokinen 1982; USGS Nonindigenous Aquatic Species Program 2013).  However, in 2022, a survey in the middle Sacramento River, found only Japanese Mystery Snails (Heterogen japonica).  Further genetic sampling will be need to determine the status of the two Mystery Snails in Pacific drainages and estuaries,

Invasion History on the East Coast:

In 1914, Cipangopaludina chinensis was found in the Muddy River, in Fenway Park, Boston, Massachusetts, where it may have been accidentally introduced with goldfish (Johnson 1918). It was soon introduced, probably by aquarium releases, and the flooding of riverside fish ponds, to the basins of several major rivers. It has now been reported from many lakes in New England, but not from tidal waters, to our knowledge (USGS Nonindigenous Aquatic Species Program 2013). In the Hudson River Basin, C. chinensis was first collected at Niskayuna, Schenectady County, New York 1920. It is now abundant in scattered locations in ponds, but has not been reported from tidal waters of the Hudson (Strayer 1987; Mills et al. 1997). In the Maritime provinces of Canada,  Cipangopaludina chinensis has been found in inland lakes in Nova Scotia, New Brunswick, and Newfoundland, with a first collection in 1955 in Yarmouth, Nova Scotia, and increasing frequency through the 1990s and 2000s (McAlpine et al. 2016).

The Chinese Mystery Snail was introduced to Fairmount Park, Philadelphia, and was established in the tidal Schuykill River by 1925 (Richards and Adams 1929). Dundee (1974) lists additional records from the Delaware River in New Jersey and Pennsylvania (PA) (Dundee 1974). Cipangopaludina chinensis was collected from ponds in Lancaster and Lebanon, PA in the Susquehanna drainage (Clench and Fuller 1965). In 2000 and 2001, many shells were found in the tidal Susquehanna at Susquehanna State Park near the mouth of Deer Creek (Fofonoff, unpublished data). No living snails were found, but the abundance of shells in shallow waters suggests a substantial population. In the Potomac River, specimens were collected at Jones Point Lighthouse, Alexandria, Virginia (VA) in 1960 (United States National Museum of Natural History Collections) and from '1/4 mile below Woodrow Wilson Bridge' (Academy of Natural Sciences of Philadelphia collection, no date, Dundee 1974). Several dead shells were found at Dyke Marsh, Alexandria VA, 1997-2000 (Fofonoff personal observation). Live snails were found on blocks anchoring settling plates near a power plant in Alexandria in 1999 (Ruiz et al., unpublished data). However, most recently collected large Mystery Snails in the Potomac appear to be Heterogen japonica (Japanese Mystery Snail) although a few fit descriptions of C. chinensis (Fofonoff, personal observation). A field survey and re-examination of museum specimens is desirable. It is possible that both species are present, but competition, hybridization, or species replacement is possible. Recent studies in the Potomac have found onlu

In the Great Lakes - St. Lawrence River basin, Cipangopaludina chinensis was first recorded in the Niagara River in 1931 and became well established by 1942. It (or its congener B. japonica) was introduced to Lake Erie by fishermen as food for Channel Catfish (Ictalurus punctatus) and became abundant in Sandusky Bay, Ohio (Mills et al. 1993). This snail became established in the St. Lawrence and Ottawa Rivers around Montreal by 1971 (Jokinen 1982; Stanczykowska et al. 1971). In the upper Great Lakes, this snail was collected in Green Bay, Wisconsin on Lake Michigan (Dundee 1974) and at the mouth of the Thunder Bay River, in Alpena, Michigan (USGS Nonindigenous Aquatic Species Program 2010).

Invasion History in Hawaii:

Cipangopaludina chinensis was introduced to the Hawaiian Islands around 1900, probably as a food item by Chinese immigrants (Cowie 1998). It was not found in a survey of coastal fresh and brackish streams in Oahu (Englund et al. 2000). It appears to be confined to fresh inland waters.

Invasion History Elsewhere in the World:

In 2009 and 2010, specimens of Cipangopaludina chinensis were found in three freshwater ponds in the Netherlands. These are the first records of this snail known from Europe (Soes et al. 2011).


Cipangopaludina chinensis is a large freshwater snail known as the Chinese Mystery Snail. The shell is dextrally coiled and somewhat globular, with a large aperture and bluntly pointed spire. The umbilicus is small and partly covered by the parietal lip of the aperture. The aperture is large and oval. The operculum is brown with concentric growth lines. The shell is thin, but strong. The adult shell has 6-7 whorls, which are strongly rounded and convex, with clear sutures. The whorls are marked with transverse growth lines and a pattern of shallow dents (malleations), like those made with a ball-peen hammer. (This is the source of the old species/subspecies name 'malleatus', from 'malleus' which is Latin for 'hammer'.) Shells which are smaller than 35 mm have a carina (keel) on the body whorl, but this becomes obscured as the shell grows. The spire forms a 60-70 degree angle. Shells may reach 60-75 mm in length. The color of the shell is light-brown to olive green, while the lip is black. Description from: Clench and Fuller 1965; Stanczykowska et al. 1971; Jokinen 1992; Smith 2000; and Soes et al. 2011.

The common name, 'Mystery Snail', is applied to several snails of the family Viviparidae, which are kept in aquaria. Instead of laying egg masses, the snails brood their young. The release of the small, crawling snails can surprise aquarium-keepers. Some authors have considered C. chinensis and Heterogen japonica (Japanese Mystery Snail, formerly C. japonica) to be conspecific, possibly ecophenotypes, while others have treated them as distinct (Clench and Fuller 1965; Jokinen 1982; Jokinen 1992). Smith (2000) provided a detailed morphological analysis, showing that the two forms show consistent differences, even as embryos in the brood pouch. Differences in the size of the larval shell (protoconch) contribute to differences in the shape of the adult shell, and the 'pointiness' of the spire, which is blunter in C. chinensis and sharper in H. japonica.. However, Ryan (2015) found many snails fitting the morphologies of C. chinensis and H. japonica, with many intemediates, in the Potomac River, and referred to the snails in the river as Bellamya spp.

There has been disagreement over the correct name for this group of viviparous snails, Smith (2000) apllied the genus name Bellamya to the Chinese and Japanese 'mystery snails). In a detailed morphological study of H. japonica, Van Bocxmaer and Strong (2016) restricted the genus Bellamya to Afrtican species, and reinstated the genus Cipangopaludina for the Asian snails.


Taxonomic Tree

Kingdom:   Animalia
Phylum:   Mollusca
Class:   Gastropoda
Subclass:   Prosobranchia
Order:   Architaenioglossa
Family:   Viviparidae
Species:   chinensis


Cipangopaludina chinensis (None, None)
Cipangopaludina chinensis malleata (None, None)
Paludina malleata (Reeve, 1863)
Viviparus chinensis malleatus (None, None)
Viviparus malleatus (None, None)
Bellamya chinensis (Smith, 2000)

Potentially Misidentified Species

Hexagen japonica

This Asian freshwater snail (Japanese Mystery Snail) is very similar, but has a more acute spire, less rounded whorls, and lacks the 'malleated' shell surface. The species are frequently confused, and once were regarded by some biologists as conspecific, so their range is uncertain (Smith 2000).  Morphological and genetic analysis has confirmed the separate status of the two species (Hirano et al. 2015; Bocxlaer and Stong 2016; Fowler et al.2022).

Viviparus georgianus
This North American freshwater snail (Banded Mystery Snail), native to the Mississippi Basin and Southeast US, is marked with four chestnut-colored bands (Clench and Fuller 1965; Jokinen 1992).



Cipangopaludina chinensis (Chinese Mystery Snail) is a large, viviparous freshwater snail. It has separate sexes, with females tending to be larger than males (up to ~150% larger). Females can produce eggs in their first year, at about 40 mm, but most of the population's egg production takes place in the 4th and 5th years (Stanczykowska et al. 1971). Females produce up to 102 embryos per brood (Crabbe 1929, cited by Jokinen 1982). Eggs are brooded in a uterus, and are hatched and released during the warmer months, at about 4 mm shell length (Jokinen 1982). A population in the St. Lawrence River, near Montreal, was estimated to have a maximum longevity of about 5 years (Stanczykowska et al. 1971).

Cipangopaludina chinensis has not been reported from brackish habitats, to our knowledge. It is generally found in lakes, ponds, or slow-flowing rivers with sandy to muddy substrates, often in densely vegetated areas (Clench and Fuller 1965; Jokinenn 1982; Jokinen 1992). It prefers waters with high levels of calcium ion, usually above 10 ppm, and a pH above 7 (Jokinen 1982; Jokinen 1992).  It feeds on bottom detritus and benthic microalgae. Some viviparids have the ability to filter-feed using their gills, but in C. chinensis, planktonic algae does not make up a significant part of the diet (Jokinen 1982; Solomon et al. 2010). These snails are prone to great population booms and busts. Predators include crayfishes (Olden et al. 2009), catfishes (Mills et al. 1993), and, probably, air-breathing predators such as gulls, raccoons, otters, etc.


attached algae


Catfish, shorebrids

Trophic Status:




General HabitatFresh (nontidal) MarshNone
General HabitatGrass BedNone
General HabitatCoarse Woody DebrisNone
General HabitatNontidal FreshwaterNone
General HabitatTidal Fresh MarshNone
General HabitatMarinas & DocksNone
General HabitatCanalsNone
Salinity RangeLimnetic0-0.5 PSU
Salinity RangeOligohaline0.5-5 PSU
Tidal RangeSubtidalNone
Vertical HabitatEpibenthicNone

Life History

Tolerances and Life History Parameters

Minimum Salinity (‰)0.2This is a freshwater species (Netherlands, Collas et al. 2017).
Minimum pH6.5New York state, range for 32 populations (Jokinen 1992)
Maximum pH7.8New York state, range for 32 populations (Jokinen 1992)
Minimum Length (mm)30Minimum size of a female with eggs, 28 mm for a mature male (Stanczykowska et al. 1971, St. Lawrence River, Quebec)
Maximum Length (mm)75Maximum size of a female, 48 mm for a male, Stanczykowska et al. 1971, St. Lawrence River, Quebec)
Broad Temperature RangeNoneCold temperate-tropical
Broad Salinity RangeNoneNontidal Limnetic-Tidal Limnetic

General Impacts

Cipangopaludina chinensis (Chinese Mystery Snail) is an attractive and popular aquarium and fishpond snail as well as a food item once sold in Chinese markets in the United States (Jokinen 1982). This species is abundant in some regions and may have had local impacts on fisheries, either as food for fishes or by interfering with fishing (Mills et al. 1993). However, it has been regarded as a relatively benign invader, with little known about its ecological impacts.

Competition: In recent mesocosm experiments, conducted in Wisconsin, C. chinensis negatively affected the abundance of the native snails Lymnaea stagnalis and Physa gyrinus, decreasing their abundance by 32% and 22% respectively (Johnson et al. 2009). In the combined presence of the Rusty Crayfish and C. chinensis, abundance of L. stagnalis declined by 90%, while C. chinensis was less affected by the presence of the crayfish, with a decreased abundance of small individuals, but no reduction in biomass (Johnson et al. 2009). With a larger size and thicker shell, C. chinensis is less vulnerable to crayfish predation than the native snails (Johnson et al. 2009). A field survey of Wisconsin lakes indicated that the effects of C. chinensis on native snail occurrence and diversity were smaller than the mesocosm study indicated. However, several species of native snails tended to be rare or absent when C. chinensis was abundant (Solomon et al. 2010).

Herbivory: In mesocom experiments, the addition of C. chinensis to an assemblage of three native snails resulted in decreased biomass of sediment and wall periphyton (Johnson et al. 2009).

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
GL-III Lake Ontario 1931 Def Estab
GL-II Lake Erie 1945 Def Estab
GL-I Lakes Huron, Superior and Michigan 1974 Def Estab
P260 Columbia River 2002 Def Estab
M090 Delaware Bay 1925 Def Estab
M130 Chesapeake Bay 1960 Def Unk
P090 San Francisco Bay 1938 Def Estab
L084 _CDA_L084 (Lake St. Clair) 2013 Def Unk
L123 _CDA_L123 (St. Lawrence River) 1971 Def Estab
L066 _CDA_L066 (Thunder Bay) 2006 Def Estab
L071 _CDA_L071 (Saginaw River) 2008 Def Estab
L106 _CDA_L106 (Niagara) 1931 Def Estab
L099 _CDA_L099 (Cuyahoga) 1965 Def Estab
L096 _CDA_L096 (Sandusky) 1968 Def Estab
L043 _CDA_L043 (Door-Kewaunee) 1974 Def Estab
L127 _CDA_L127 (English-Salmon) 2003 Def Estab
P135 _CDA_P135 (Mad-Redwood) 2009 Def Estab
M130 Chesapeake Bay 1960 Def Unk

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude


Abeyrathna, Wijesooriya Arachchilage Nimanthi Upeksha; Sanders, Shawn H.; Barreto, Ashley; Davinack, (2023) First genetically confirmed report of the Japanese mystery snail, Heterogen japonica (Martens, 1861) from California more than a century after its first introduction, BioInvasions records 12: In press

Bury, Jennifer A.; Sietman, Bernard E.; Karns, Byron N. (2007) Distribution of the non-native viviparid snails, Bellamya chinensis and Viviparus georgianus, in Minnesota and the first record of Bellamya japonica from Wisconsin, Journal of Freshwater Ecology 22(4): 697-703

Clench, William J.; Fuller, Samuel L. H (1965) The genus Viviparus in North America, Occasional Papers on Mollusks, Museum of Comparative Zoology, Harvard University 2(32): 385-412

Cohen, Andrew N.; Carlton, James T. (1995) Nonindigenous aquatic species in a United States estuary: a case study of the biological invasions of the San Francisco Bay and Delta, U.S. Fish and Wildlife Service and National Sea Grant College Program (Connecticut Sea Grant), Washington DC, Silver Spring MD.. Pp. <missing location>

Cohen, Andrew N.; Chapman, John T. (2005) <missing title>, San Francisco Estuary Institute, San Francisco. Pp. <missing location>

Cowie, Robert H. (1998) Patterns of introduction of non-indigenous non-marine snails and slugs in the Hawaiian Islands., Biodiversity and Conservation 7: 349-368

Dillon, R. T. Jr.; Watson, B.T.; Stewart, T. W.; Reeves, W. K. 2006-2024 The freshwater gastropods of North America.

Dundee, Dee S. (1974) Catalog of introduced molluscs of eastern North America (North of Mexico), Sterkiana 55: 1-37

Englund, R.A.; Arakaki, K.; Preston, D.J.; Coles, S.L.; Eldredge, L.G. (2000) <missing title>, Hawaii Biological Survey, Bishop Museum, Honolulu. Pp. <missing location>

Havel, John E. (2011) Survival of the exotic Chinese mystery snail (Cipangopaludina chinensis malleata) during air exposure and implications for overland dispersal by boats, Hydrobiologia 668: 195-202

Johnson, C. W. (1918) Viviparus malleatus and contectoides in Massachusetts, Nautilus 31(3): 107-108

Johnson, Pieter T. J.; Olden, Julian D.; Solomon, Christopher T.; Vander Zanden, M. Jake (2009) Interactions among invaders: community and ecosystem effects of multiple invasive species in an experimental aquatic system, Oecologia 159: 161-170

Jokinen, Eileen H. (1982) Cipangopaludina chinensis (Gastropoda: Viviparidae) in North America, review and update, Nautilus 96(3): 89-95

Jokinen, Eileen H. (1992) The freshwater snails (Mollusca: Gastropoda) of New York State, New York State Museum Bulletin 482: 1-89

Karatayev, Alexander Y. and 5 authors (2012) Exotic molluscs in the Great Lakes host epizootically important trematodes, Journal of Shellfish Research 31: 885-894

Karatayev, Alexander Y.; Burlakova, Lyubov E.; Karatayev, Vadim A; Padilla, Dianna K. (2009) Introduction, distribution, spread, and impacts of exotic freshwater gastropods in Texas, Hydrobiologia 619: 181-194

Kingsbury, S. E.; McAlpine, Donald F.; Cheng, Y. ; Parker, E.; Campbell, L .M. (2021) A review of the non-indigenous Chinese mystery snail,Cipangopaludina chinensis (Viviparidae), in North America, with emphasis on occurrence in Canada and the potential impact on indigenous aquatic species, Environmental Reviews 29: 182-200
DOI: 10.1139/er-2020-0064

Marsden, J. Ellen; Hauser, Michael (2009) Exotic species in Lake Champlain, Journal of Great Lakes Research 35: 250-265

McAlpine, Donald F. and 8 authors (2016) Occurrence of the Chinese mystery snail, Cipangopaludina chinensis (Gray, 1834) (Mollusca: Viviparidae) in the Saint John River system, New Brunswick, with review of status in Atlantic Canada, BioInvasions Records 5: In press

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

Mills, Edward L.; Scheuerell, Mark D.; Carlton, James T.; Strayer, David (1997) Biological invasions in the Hudson River: an inventory and historical analysis., New York State Museum Circular 57: 1-51

Olden, Julian D.; Larson, Eric R.; Mims, Meryl C. (2009) Home-field advantage: native signal crayfish (Pacifastacus leniusculus) out consume newly introduced crayfishes for invasive Chinese mystery snail (Bellamya chinensis), Aquatic Ecology 43: 1073-1084

Pachelle, Paulo P.; Carvalho, Lena; , Alves, Douglas F. R.; Anker, Arthur (2020) A revision of the Brazilian species of Lysmata Risso, 1816 (Decapoda: Caridea: Lysmatidae), with discussion of the morphological characters used in their identification, Zootaxa 4789(1): 55-90

Richards, Horace G., Adams, Joseph W. (1929) Viviparus malleatus in Philadelphia, Nautilus 42(4): 141-142

Smith, Douglas G. (2000) Notes on the taxonomy of introduced Bellamya (Gastropoda: Viviparidae) species in northeastern North America., Nautilus 114(2): 31-37

Soes, D. Menno; Majoor, Gerard D.; Keulen, Stef M.A. (2011) Bellamya chinensis (Gray, 1834) (Gastropoda: Viviparidae), a new alien snail species for the European fauna, Aquatic Invasions 6: Corrected Proof

Solomon, Christopher T.; Olden, Julian D. Johnson, Pieter T. J.; Dillon Jr., Robert T.; Vander Zanden, M. Jake (2010) Distribution and community-level effects of the Chinese mystery snail (Bellamya chinensis) in northern Wisconsin lakes, Biological Invasions 12: 1591-1605

Stanczykowska, Anna, Magnin, Etienne, Dumouchel, André (1971) Etude de trois populations de Viviparus malleatus (Reeve) de la region de Montreal. 1. Croissance, fecondite, biomasse, et production annuelle., Canadian Journal of Zoology 49: 1431-1441

Stewart, Timothy; Dillon, Robert T. (2004) Species composition and geographic distribution of Virginia's freshwater gastropod fauna: A review using historical records., American Malacological Bulletin 10(1/2): 79-91

Stimpson, W. A. (1860) rodromus descriptionis animalium evertebratorum, quae in Expeditione ad Oceanum Pacificum Septemtrionalem, a Republica Federata missa, C. Ringgold et J. Rodgers, observavit et descriptist, Proceedings of the Academy of Natural Sciences of Philadelphia <missing volume>: <missing location>

Stimpson, W. A. (1860) rodromus descriptionis animalium evertebratorum, quae in Expeditione ad Oceanum Pacificum Septemtrionalem, a Republica Federata missa, C. Ringgold et J. Rodgers, observavit et descriptist, Proceedings of the Academy of Natural Sciences of Philadelphia 12: 22-47

Strayer, David (1987) Ecology and zoogeography of the freshwater mollusks of the Hudson River Basin, Malacological Review 20: 1-68

Sytsma, Mark D.; Cordell, Jeffrey R.; Chapman, John W.; Draheim, Robyn, C. (2004) <missing title>, Center for Lakes and Reservoirs, Portland State University, Portland OR. Pp. <missing location>

USGS Nonindigenous Aquatic Species Program 2003-2024 Nonindigenous Aquatic Species Database.

Wolfert; David R.; Hiltunen, Jarl K. (1968) Distribution and abundance of the Japanese snail, Viviparus japonicus, and associated macrobenthos in Sandusky Bay, Ohio, Ohio Journal of Science 68(1): 32-40