Potamopyrgus antipodarum
Potamopyrgus antipodarum
(New Zealand mudsnail)
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Potamopyrgus antipodarum (J.E. Gray, 1853)

Common name: New Zealand mudsnail

Synonyms and Other Names: Potamopyrgus jenkinsi, Hydrobia jenkinsi

Taxonomy: available through www.itis.govITIS logo

Identification: Potamopyrgus antipodarum has a dextral (right-handed coiling), elongated shell with 7-8 whorls separated by deep grooves. The operculum is thin and corneus with an off-centre nucleus from which paucispiral markings (with few coils) radiate. The aperture is oval and its height is less than the height of the spire. Some morphs, including many from the Great Lakes, exhibit a keel in the middle of each whorl; others, excluding those from the Great Lakes, exhibit periostracal ornamentation such as spines for anti-predator defense (Holomuzki and Biggs 2006, Levri et al. 2007, Zaranko et al. 1997).  Shell colors vary from gray and dark brown to light brown.

Size: The snail is usually 4 to 6 mm in length in the Great Lakes, but grows to 12 mm in its native range (Levri et al. 2007, Zaranko et al. 1997).

Native Range: The freshwater streams and lakes of New Zealand and adjacent small islands; it is naturalized in Australia and Europe (Hall et al. 2003).

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Nonindigenous Occurrences: This snail was first discovered in the middle portion of the Snake River in Idaho in 1987.  By 1995, the mudsnail had reached the Madison River in Montana and into Yellowstone National Park the following year (Wyoming). It is also established in Minidoka National Wildlife Refuge, Idaho (USFWS 2005).  Since then, they have been found in the Madison River and several other rivers in and near Yellowstone National Park. Populations were discovered near the mouth of the Columbia River in Oregon in 1997, and the Owens River in California.  Since then, this species is becoming very widespread in California. This species became established in the lower Columbia River, Washington about 1999 (M. Sytsma, pers. comm.) and in the Colorado River in northern Arizona (M. Anderson, pers. comm.) by 2002.  In Utah, the first mudsnails were found about 2001 and have since been found in the Green River and many others. In 2004, mudsnails were found in small Colorado creek near Boulder (P. Walker, pers. comm.).

Great Lakes - P. antipodarum was found established in Lake Ontario in 1991 (Zaranko et al. 1997) and in Lake Erie (Ohio and Pennsylvania) in 2005 (Levri et al. 2007). It may also be established in Duluth-Superior Harbor (Minnesota/Wisconsin) of Lake Superior, where some individuals were found in 2001 (Grigorovich et al. 2003). They have also been collected from southwestern Lake Ontario, New York, the Welland Canal and northeastern Lake Ontario, Ontario, Canada as well as Lake Superior at Thunder Bay, Ontario, Canada in 2001. A population was discovered in Lake Michigan, off Waukegan, Illinois in 2006 (T. Nalepa, pers.comm.).

Ecology: Potamopyrgus antipodarum is a nocturnal grazer, feeding on plant and animal detritus, epiphytic and periphytic algae, sediments and diatoms (Broekhuizen et al. 2001, James et al. 2000, Kelly and Hawes 2005, Parkyn et al. 2005, Zaranko et al. 1997).

The snail tolerates siltation, thrives in disturbed watersheds, and benefits from high nutrient flows allowing for filamentous green algae growth. It occurs amongst macrophytes and prefers littoral zones in lakes or slow streams with silt and organic matter substrates, but tolerates high flow environments where it can burrow into the sediment (Collier et al. 1998, Death et al. 2003, Holomuzki and Biggs 1999, Holomuzki and Biggs 2000, Negovetic and Jokela 2000, Richards et al. 2001, Schreiber et al. 2003, Suren 2005, Weatherhead and James 2001, Zaranko et al. 1997).

Potamopyrgus antipodarum is ovoviviparous and parthenogenic. Native populations in New Zealand consist of diploid sexual and triploid parthenogenically cloned females, as well as sexually functional males (less than 5% of the total population). All introduced populations in North America are clonal, consisting of genetically identical females. The snail produces approximately 230 young per year. Reproduction occurs in spring and summer, and the life cycle is annual (Gerard et al. 2003, Hall et al. 2003, Lively and Jokela 2002, Schreiber et al. 1998, Zaranko et al. 1997). They are found in the Great Lakes at depths of 4-45 m on a silt and sand substrate (Levri et al. 2007, Zaranko et al. 1997)

This species is euryhaline, establishing populations in fresh and brackish water. The optimal salinity is probably near or below 5 ppt, but P. antipodarum is capable of feeding, growing, and reproducing at salinities of 0–15 ppt and can tolerate 30–35 ppt for short periods of time (Costil et al. 2001, Gerard et al. 2003, Jacobsen and Forbes 1997, Leppakoski and Olenin 2000, Zaranko et al. 1997). It tolerates temperatures of 0–34°C (Cox and Rutherford 2000, Zaranko et al. 1997).

Potamopyrgus antipodarum can survive passage through the guts of fish and may be transported by these animals (Bruce 2006). It can also float by itself or on mats of Cladophora spp., and move 60 m upstream in 3 months through positive rheotactic behavior (Zaranko et al. 1997). It can respond to chemical stimuli in the water, including the odor of predatory fish, which causes it to migrate to the undersides of rocks to avoid predation (Levri 1998). Common parasites of this snail include trematodes of the genus Microphallus (Dybdahl and Krist 2004).

Means of Introduction: Potamopyrgus antipodarum was most likely introduced to the Great Lakes in ships from Europe, where there are nonindigenous populations (Leppäkoski & Olenin 2000, Levri et al. 2007, Zaranko et al. 1997) or in the water of live gamefish shipped from infested waters to western rivers in the United States.

Status: This species is established in Lake Ontario, Lake Erie, Lake Michigan and most likely in Lake Superior and is expanding its range within the Great Lakes basin (Levri et al. 2007).  In the Great Lakes, the snail reaches densities as high as 5,600 per square meter. ( Levri et al. 2007, Zaranko et al. 1997).  Also established in all western states where it is found in the US.

Impact of Introduction: A) Realized: None known.

B) Potential: Likely to find all shallower waters (<50 m depth) as suitable habitat. High spread potential (USEPA 2008). Abundant populations of introduced P. antipodarum may outcompete other grazers and inhibit colonization by other macroinvertebrates (Kerans et al. 2005). In Europe, P. antipodarum causes declines in species richness and abundance of native snails in constructed ponds (Strzelec 2005). By contrast, in one Australian stream, increasing densities of P. antipodarum are positively correlated with density and species richness of native invertebrates, possibly due to coprophagy (ingestion of the snail's faeces) (Schreiber et al. 2002). In geothermal streams in the western U.S., P. antipodarum reaches densities of 300,000 snails m2 and alters nutrient (nitrogen and carbon) flows, consumes large amounts of GPP, accounts for most of the invertebrate production (Hall et al. 2003).  P. antipodarum has yet to colonize streams in the Great Lakes basin, but these are the habitats in which the snail is expected to exert significant impacts (Levri et al. 2007). 

Densities have reached over 300,000 individuals per square meter in the Madison River. A species as prolific as this has potential to be a biofouler at facilities drawing from infested waters. It also may compete for food and space occupied by native snails. There is some evidence in their native range that trout may avoid these snails as a prey.

It is suspected that they can alter primary production of streams and spread rapidly (USEPA 2008).

Remarks: Potamopyrgus antipodarum is synonymous with P. jenkinsi and Hydrobia jenkinsi.

Mudsnail populations consist mostly of asexually reproducing females that are born with developing embryos in their reproductive system.  This species can be found in all types of aquatic habitats from eutrophic mud bottom ponds to clear rocky streams. It can tolerate a wide range of water temperatures (except freezing), salinity, and turbidity in clean as well as degraded waters. They feed on dead and dying plant and animal material, algae, and bacteria. Its tolerance of a broad range of ecological factors make the possibility of further spread likely. In moist conditions, this snail can withstand short periods of desiccation (Richards et al. 2004).

The public should be careful to decontaminate fishing and sporting equipment so as not to spread existing populations or start new ones.  Regulations on commercial shipping of this species are in effect. The species supports a number of parasites in its native range, but none have been found on North American populations examined.

References: (click for full references)

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Hall, R.O., Jr., J.L. Tank, and M.F. Dybdahl. 2003. Exotic snails dominate nitrogen and carbon cycling in a highly productive stream. Frontiers in Ecology and the Environment 1(8):407–411.

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

Revision Date: 6/26/2014

Citation Information:
Benson, A.J., R.M. Kipp, J. Larson, and A. Fusaro. 2017. Potamopyrgus antipodarum. USGS Nonindigenous Aquatic Species Database, Gainesville, FL.
https://nas.er.usgs.gov/queries/FactSheet.aspx?SpeciesID=1008 Revision Date: 6/26/2014

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Citation information: U.S. Geological Survey. [2017]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [2/20/2017].

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