> Habitat & Distribution

Although native to southeast Asia, Cipangopaludina japonica (and the closely related C. chinensis) were first introduced to North America in the late 1890s and have now spread throughout the United States, especially in New England and the Midwest (Cordeiro 2002).  The earliest record in our database is a 1962 lot in the USNM from Lake Warren, Pennsylvania.  We also have several records from the mid-1970s and mid-1980s in Ohio, Pennsylvania, and Virginia.  The modern range of C. japonica extends throughout the drainages of The Ohio and Atlantic drainages south to the Carolinas, although not, as yet, the Tennessee/Cumberland.  Populations reach maximum abundance in lentic environments, especially artificial impoundments, and in large, slow-moving rivers.  FWGNA incidence rank I-4.

> Ecology & Life History

The initial introduction of Cipangopaludina into the New World seems to have occurred in the oriental markets of the American west coast, as an item of food (Jokinen 1982).  Rather incongruously with our western experience, concern has been expressed that populations of C. chinensis in Japanese rice paddies may be in decline (Nakanshi et al. 2014).

Cipangopaludina japonica populations seem to have arrived in the Carolinas in the mid-1990s (Anon. 1995) and spread rapidly through large hydroelectic impoundments in both states, including Lakes Norman, Wylie, Bowen, Greenwood, Hartwell, Wateree, Marion and Moultrie.  An anecdote relayed to me by North Carolina Fish and Game officials in 2005, involving fishermen of Laotian descent harvesting C. japonica from High Rock Reservoir by night, suggests that this phenomenon may have been promoted by artificial “seeding.”  See my essay of 6Oct05 from the link below for more.

“Water gardening” has, however, become a popular hobby throughout much of the United States.  The retail stores that have developed to supply hobbyists with pond liners, pumps, goldfish and ornamental lilies also commonly stock “mystery snails” or “trap-door snails” to clarify the water. These are almost always Cipangopaludina.  So, it is also certainly possible that most of the recent introductions in this country are simply excess snails casually released by hobbyists and water gardeners.

That Cipangopaludina populations can, in fact, clarify the water in small ornamental ponds attests to their efficiency as filter-feeders. They probably also graze, or at least scavenge excess fish food (Raut 1986). But they most certainly do not consume macrophytes, lest their popularity with water gardeners who invest heavily in such plants should be short-lived.

Johnson et al. (2009) reported some experimental evidence that Cipangopaludina invasion might have a negative impact on native populations of pulmonate snails, a finding that seems to be supported by the laboratory feeding experiments of Sura & Mahon (2011).  The field surveys of Solomon et al. (2010) found no evidence of the phenomenon in Northern Wisconsin, however.  Solomon and colleagues did document positive correlations between the presence of Cipangopaludina and several general measures of lake productivity, such as conductivity and Secchi turbidity. But additional evidence of correlations between Cipangopaludina and such measures of lake disturbance as boat landings and shoreline housing suggested to Solomon and his colleagues that Cipangopaludina populations had not “saturated the landscape” even in Wisconsin, where their invasion apparently dates to the 1950s.  See my essay of 18Dec09 from the link below for more.

Although we are aware of no good study following the life history of C. japonica, Khan & Chaudhuri (1984) reported six-month maturation, followed by iteroparous reproduction, in an Indian population of Bellamya bengalensis (Bii of Dillon 2000: 156- 162).

Adult Cipangopaludina can survive several weeks of aerial exposure (Havel 2011).  Populations of both species sometimes seem to reproduce explosively, then suffer dramatic crashes, as might be associated with spent-salmon semelparous reproduction (Vol 4, essay 10).  It seems more likely to us, however, that such mortalities may be better attributable to the colonization of marginal habitats as a consequence of population flushes accompanying invasion.  See our Cipangopaludina chinensis species page for a more complete discussion of population dynamics.

> Taxonomy & Systematics

Originally described by von Martens in the genus Paludina, the nomen japonica was transferred to Cipangopaludina by Hannibal (1912), appearing either as a subgenus of Viviparus (Clench & Fuller 1965) or accorded full generic status.  Smith (2000) pointed out that the genus Bellamya (Jousseaume 1886) is generally preferred throughout the Old World, however, the characters used by Hannibal to differentiate Cipangopaludina being generally variable or correlated with size.  The classification system adopted by the FWGNA project followed Smith from our inception until 2021.  More recently, however, the DNA sequence data developed by Stelbrink et al. (2020) have suggested a re-reassignment of the large oriental viviparids introduced into North America back to Cipangopaludina, leaving Bellamya as a genus for African species.  See my essay of 9Mar21 from the link below.

The two species introduced here, C. chinensis and C. japonica, have often been confused and sometimes even synonymized (eg, post of 5Aug14, below).  But Smith found no morphological overlap between the former (bearing a shell with more rounded shoulders) and the latter (with a more turreted shell) and recommended that the specific distinction be retained.  See my blog post of 18Dec09 for a figure comparing the shell morphologies the two species, both as adults and as juveniles, where the distinction is stronger.

> Maps and Supplementary Resources

• Cipangopaludina distribution in Atlantic drainages (2023)
• Cipangopaludina in the drainage of The Ohio (2019)
• Pretty photo of living C. japonica, courtesy of Chris Lukhaup.
  
• Large-scale mortality of C. japonica on the Neabsco River, northern Virginia, summer 2010.
  

> Essays

• Cipangopaludina was mentioned parenthetically in my 29Oct03 essay on Invasive Viviparids in South Carolina. The distributional info is a bit obsolete, but there are several additional photos.
• See my Bellamya News of 6Oct05 for items about Cipangopaludina Ranching in North Carolina, Cipangopaludina Roundup in Massachusetts, and Cipangopaludina as a Model for Invertebrate Anatomy.
• The Community Consequences of Bellamya Invasion in Wisconsin lakes were explored in my FWGNA blog post of 18Dec09.  There was also a nice photo comparing C. chinensis to C. japonica, both juvenile and adult.
• My FWGNA blog post of 12Sept11, Dispatches from the Viviparid Front, included one item on a citizen's monitoring effort in Wisconsin (with links to some good references) and a second item on controlling Cipangopaludina in Ontario by hand-picking. 
• In Just Before The Bust (5Aug14) I described a C. japonica population explosion in the tailwaters of the the Wateree Dam in central South Carolina.  That post featured several striking in situ photos, including a high resolution jpeg of a "bed" of Cipangopaludina apparently filter feeding like mussels.
• I reviewed the Cipangopaludina records in the USGS Nonindigenous Aquatic Species database in my post of 16Oct15, To Only Know Invasives.  That essay featured two photos of C. chinensis shells, one of which was incorrectly labeled japonica by the USGS.
• Unsurprisingly, Cipangopaludina of many species are widely retailed through the online aquarium trade.  See my post of 24Jan18, Snails by Mail.
• I reviewed A Gene Tree for the Worldwide Viviparidae published by Stelbrink et al. (2020) in my post of 9Mar21.  That essay focused on the question of genus assignment for our big oriental viviparids here in North America, Cipangopaludina or Bellamya?

> References

Anon. (1995) Exotic Aquatics show up in South Carolina. South Carolina Wildlife, July-August, p. 48.
Anon. (2001) Technical Comittee Reports/Concerns, Exotics. American Fiseries Society Southern Division Newsletter, July, p. 16.
Benson, A. J., Fuller, P. L, & Jacono, C. C. (2001) Summary report of nonindigenous aquatic species in US Fish & Wildlife Service Region 4. USFWS, Arlington, Va, p. 60.
Chaine, N. M., C. Allen, K. Fricke, D. Haak, M. Hellman, R. Kill, K. Nemec, K. Pope, N. Smeenk, B. Stephen, D. Uden, K. Unstad & A. VanderHam (2012)  Population estimate of Chinese mystery snail (Bellamya chinensis) in a Nebraska reservoir.  BioInvasions Records 1: 283-287.
Clench, W. & Fuller, S. (1965) The genus Viviparus in North America. Occas. Pprs. on Mollusks, Mus. Comp. Zool. Harvard, 2, 385-412.
Cordeiro, J. R. (2002) Proliferation of the Chinese mystery snail, Cipangopaludina chinensis malleata (Reeve, 1863) throughout Connecticut [Abstract]. Program and Abstracts of the 68th Meeting of the American Malacological Society, Charleston, SC (R. T. Dillon, ed.) p. 37.
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Havel, J.E. (2011)  Survival of the exotic Chinese mystery snail (Cipangopaludina chinensis malleata) during air exposure and implications for overland dispersal by boats.  Hydrobiologia  668(1):195-202.
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Nakanishi, K., K-I. Takakura, R. Kanai, K. Tawa, D. Murakami and H. Sawada (2014)  Impacts of environmental factors in rice paddy fields on abundance of the mud snail (Cipangopaludina chinensis laeta).  Journal of Molluscan Studies  80(4):460-463.
Raut, S. (1986) Inhibition of fish growth by the freshwater snail Bellamya bengalensis. Environ. Ecol., 4: 332-333.
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Stelbrink, B., R. Richter, F. Köhler, F. Riedel, E. Strong, B. Van Bocxlaer, C. Albrecht, T. Hauffe, T. Page, D. Aldridge, A. Bogan, L-N. Du, M. Manuel-Santos, R. Marwoto, A Shirokaya, and T. Von Rintelen (2020)  Global diversification dynamics since the Jurassic: Low dispersal and habitat-dependent evolution explain hotspots of diversity and shell disparity in river snails (Viviparidae).  Systematic Biology 69: 944 – 961.
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