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   Bellamya chinensis (mollusc)
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      Bellamya chinensis (Photo: Amy Benson, USGS) - Click for full size
    Taxonomic name: Bellamya chinensis (Gray, 1834)
    Synonyms: Cipangopaludina chinensis malleata, Cipangopaludina chinensis (von Martens, 1861), Cipangopaludina malleata, Paludina japonicus, Paludina malleata, Viviparus japonicus (von Martens), Viviparus malleatus, Viviparus stelmaphora, Viviparus chinensis malleatus
    Common names: Asian apple snail, Asian freshwater snail, Chinese mystery snail, Chinese mysterysnail, mystery snail, Oriental mystery snail, trapdoor snail
    Organism type: mollusc
    Bellamya (=Cipangopaludina) chinensis or Chinese mystery snail is a freshwater gastropod native to southeast Asia, Japan, China, Korea and eastern Russia. It has been introduced to Canada and much of the United States probably via the aquarium trade, water gardening industry or for culinary purposes and first documented in Chinese markets of San Francisco, and has recently been discovered in the Netherlands which represents the first record for Europe. It may outcompete native snails and transmit human parasites, but very little is known about its ecological impacts in invaded systems and more research is necessary.
    Bellamya chinensis is a large freshwater snail that may reach a shell length of up to 70 mm (measured from the apex to the basal inflection of the aperture) and dry tissue mass of ~1 g (Olden et al., 2009; Solomon et al., 2010). It exhibits a robust morphology with a width to height ratio of 0.74-0.82. The shell is globose and has 6 to 7 whorls that are convex and have a clear suture. It exhibits light coloration as a juvenile, which darkens to olive green, greenish brown, brown or reddish brown as an adult. The inner coloration is white to pale blue and the lip is a black colour. B. chinensis have a thick outer shell and a hard operculum flap or trapdoor covering the shell opening (aperture) that affords a high degree of protection from predators and unfavourable environmental conditions.

    In juveniles the last shell whorl displays a distinct cartilaginous ridge (carina) and the shell contains grooves with 20 striae/mm between each groove. Juveniles also have a detailed pattern on their periostracum consisting of 2 apical and 3 body whorl rows of hairs with long hooks on the ends, distinct ridges and many other hairs with short hooks.

    Considerable variation between individuals exists, and distinct shell variations have been designated as morphotypes assumed to reflect variations in allometric shell growth in different environmental regimes (AIS, 2005; Prezant et al., 2006; Benson, 2007; Kipp & Benson, 2011; Soes et al., 2011).

    Similar Species
    Bellamya japonica

    Occurs in:
    lakes, wetlands
    Habitat description
    Bellamya chinensis occurs in large lentic or slow-moving lotic systems with soft, muddy or silty bottoms (Benson, 2007; Distler, 2003). Such suitable freshwater bodies include rivers, streams, ponds, lakes, rice paddies, roadside ditches and irrigation canals (Jokinen, 1982; AIS, 2005). Adults are typically found on surfaces or partially buried under mud or silt, while juveniles are often found in crevices or under rocks (Prezant et al., 2006). It is a temperate species with a lower limit of 0 °C and upper limit of 30 °C (Kipp & Benson, 2008 in Karatayev et al., 2009), and thus cannot tolerate high summer temperatures in the United States (Karatayev et al., 2009).

    It has been found in depths of 0.2-3 m and waters with pH of 6.5-8.4, conductivity of 63–400 μmhos/cm, and concentrations of calcium (5-97 ppm), magnesium (13-31 ppm), oxygen (7-11ppm), and sodium ( 2–49 ppm) (Jokinen 1982; Jokinen 1992 in Kipp & Benson, 2011). It can tolerate conditions in stagnant waters near septic tanks (Perron & Probert, 1973 in Kipp & Benson, 2011). A recent study also suggests that B. chinensis is highly resistant to desiccation, giving potential for overland transport via boats (Havel, 2010).

    General impacts
    Bellamya chinensis is a relatively large snail species that can reach very high densities of up to 40 per m² (Soes et al., 2011; Johnson et al., 2009). While negative impacts on native snail species and ecosystems are expected (Bury et al., 2007) very little is known about its ecological impacts and significance in invaded systems (Johnson et al., 2009; Solomon et al., 2010; Soes et al., 2011)

    Competition: Presence of B. chinensis was found to cause substantial declines in the growth and abundance of native Physella gyrina and Lymnaea stagnalis snails in mesocosm experiments, probably through competition for food (Johnson et al., 2009). However such negative impacts on native gastropod assemblages have not yet been confirmed in field studies. Solomon et al. (2010) found no difference in snail assemblage structure associated with B. chinensis presence or abundance at the scale of an entire lake, although some native snail species tended not to occur at sites where B. chinensis was abundant.

    Ecosystem change: In a mesocosm experiment B. chinensis grazing was found to reduce algal biomass, algal species composition and increase the N: P ratio in the water column. Such effects may have important ecological consequences (Johnson et al., 2009).

    Interaction with other invasive species: In a mesocosm experiment in Wisconsin, the dual effects of predation by an invasive crayfish (Orconectes rusticus) and competition by B. chinensis were found to have more severe impacts on native snail species than either invader alone. Due to its large size and thicker shell B. chinensis was less vulnerable to predation by this crayfish. The combined impact of both invasive species was found to extirpate one native snail species and reduce the abundance of a second by >95%. This may be because O. rusticus reduces native snail abundance via predation but has limited effects on B. chinensis, thus promoting additional food resources for B. chinensis (Johnson et al., 2009).

    An experimental study in Washington suggests that B. chinensis may facilitate establishment and exacerbate the establishment success and ecological impacts of an invasive crayfish (Orconectes virilis) by providing an abundant prey resource (i.e. invasional meltdown). This hypothesis requires further research and testing (Olden et al., 2009).

    Human health: B. chinensis is also the host for several helminth parasites that affect humans in native Asia. Thus it may serve as a vector for parasites and diseases, including human intestinal fluke (Chung & Jung, 1999; Havel, 2010; NAPIS, 2010). However there is little data to support this (Soes et al., 2011), and there have been no reported cases involving human intestinal fluke transmitted by B. chinensis in the United States (Bury et al., 2007).

    Human nuisance: Shells may clog the screens of water intake pipes and thus inhabit the flow of water (AIS, 2005). Additionally, dead and decaying shells can form large windrows on lake shores, which is viewed as a nuisance by residents in some regions (Bury et al., 2007). In the Laurentian Great Lakes, fisherman often made seine hauls containing “2 tons” of snails, which were likely B. chinensis or B. japonica (Wolfert & Hiltunen, 1968).

    Other: B. chinensis were found to provide a novel food resource for both native and invasive crayfish in Washington, despite their thick shell and trapdoor defense behaviour. For all snail size classes native Pacifastacus leniusculus was able to consume greater numbers of snails than an invasive crayfish species. Whether this translates into P. leniusculus having a competitive advantage over invasive crayfish in a natural setting is unknown (Olden et al., 2009).

    Bellamya chinensis is edible and is sold in Chinese food markets in the United States (Benson, 2007). B. chinensis may also be useful in eliminating sewage sludge and heavy metals in rice paddy soil (Kurihara & Suzuki, 1987).
    Oriental mystery snails include the closely related Japanese mystery snail (Bellamya japonica) and the Chinese mystery snail (Bellamya chinensis). However the taxonomy of introduced populations of Oriental mystery snails is confusing and there are many scientific names in use. In older literature the genus name Cipangopaludina is commonly used for both species. Smith (2000) argues that Cipangopaludina is a subgenus of Bellamya. The current literature has preferred the name Bellamya (Soes et al., 2011), which is used throughout this document.

    Two subspecies or variations of Bellamya chinensis are recognized: chinensis and malleata (AIS, 2005; IT IS, 2009).

    Geographical range
    Native range: Eastern Russia, China, Japan, Java, Korea, Myanmar (Burma), Philippines, Taiwan, Vietnam.
    Introduced range: Alaska, Canada, continental United States, Hawaii, Netherlands.
    Introduction pathways to new locations
    Horticulture: B. chinenis may have been transported to the United States as a passive attachment on ornamental lotus plants (Smith, 1995 in Martin, 1999).
    Live food trade: This species is thought to have been brought to the United States from Japan as a food source for humans (Wood, 1892).
    Other: B. chinensis was intentionally stocked as food for the channel catfish, Ictalurus punctatus in Lake Erie in the 1940s (Wolfert & Hiltunen, 1968; Mills et al., 1993).
    Pet/aquarium trade: Deliberate release from aquariums is a potential vector for the spread of Bellamya chinensis. Rixon et al. (2005) found that it was only sold in 10% of aquarium stores surveyed in the Great Lakes region, although it was the only mollusc species in the study predicted to survive Great Lakes winter temperatures. By contrast, a survey of aquarium stores in Seattle, Washington did not find B. chinenis (Strecker et al., 2011).
    Ship/boat hull fouling: Recreational boaters may tranport this snail to new locations as it attaches to macrophytes which often infest boat hulls. B. chinensis can survive for long periods of air exposure, making transport between lakes on overland vectors such as trailered boats likely (Havel, 2010). Indeed, a survey of 21 lakes found that this snail was more likely to occur at sites near boat launches (Solomon et al., 2009).
    Management information
    Preventative measures: It is currently legal to own B. chinensis in the United States. Rixon et al. (2005) recommend the erection of trade restrictions regarding the sale, importation or breeding of high-risk species in areas where they have potential for establishing populations. In particular, vectors of invasion such as live fish marks and the aquarium industry should be addressed (Rixon et al., 2005; Strecker et al., 2011). It does not feed on macrophytes, making it popular with aquarists and water gardeners.

    B. chinensis is thought to be spread overland by attachment to macrophytes on boat hulls. Changing human behaviour such as encouraging removal of macrophytes may reduce the spread of this snail, as well as other invasive species of concern (Havel, 2010).

    Chemical control: Copper sulfate is approved by the U.S. Environmental Protection Agency as a snailicide commonly used for control of other invasive snail species. It has recently been used for the first time against B. chinensis in Jackson County, Oregon. While 100% eradication has not been achieved, it may be a successful method for controlling populations (Freeman, 2010).

    Bellamya chinensis is a filter feeder and detritivore, but also browses on microalgae (Dillon, 2000).. Based on examination of gut contents it feeds non-selectively on inorganic-organic debris and epiphytic-benthic algae, predominantly diatoms (Jokinen, 1982). It does not feed readily on plants; snails fed on spinach were found to perform poorly compared to those fed with detritus (Mohrman, 2007 in Soes et al., 2011). Carbon stable isotope ratios of B. chinensis collected from one Wisconsin lake lakes suggest heavy reliance on benthic resources and little if any reliance on pelagic resources (Solomon et al., 2010), although this has not been tested.
    Bellamya chinensis is viviparous, giving birth to fully developed juveniles (Dillon, 2000). Females continuously release small numbers of juveniles (Havel, 2010), reportedly producing in the order of 65 live offspring per year (Keller et al., 2006). Males of B. chinensis can be identified by the presence of a modified right tentacle that acts as a penis.

    Prezant et al. (2006) found that in the presence of crayfish predators B. chinensis may exhibit predator-induced defensive responses. Females in the presence of crayfish released significantly more juveniles than control females, and juveniles were smaller, more variable in size and had higher organic content of shells. The generally smaller size of juveniles released in the presence of a predator reflects a faster rate of generation and passage through the uterus.

    Lifecycle stages
    All stages of development (from newly fertilized ova to 5 mm long fully shelled juveniles) are found simultaneously within the uterine sac of females (Prezant et al., 2006). Changes in the parent’s environment, including exposure to predators may be reflected in biochemical, physiological and morphological changes in developing young. For example, females in the presence of crayfish gave birth to higher numbers of smaller young that had higher organic content of shells (Prezant et al., 2006).

    Young are born live and fully formed and growth is allometric (the height of the shell increases more rapidly than the width). The lifespan is four to five years (Jokinen, 1982), and individuals have the potential to overwinter in cold conditions (Rixon et al., 2005).

    Reviewed by: Julian Olden, School of Aquatic and Fishery Sciences, University of Washington
    Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
    Last Modified: Friday, 15 April 2011

ISSG Landcare Research NBII IUCN University of Auckland