Potamopyrgus antipodarum (J.E. Gray, 1853)

Common Name: New Zealand mudsnail

Synonyms and Other Names:

Potamopyrgus jenkinsi, Hydrobia jenkinsi



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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).


Great Lakes Nonindigenous Occurrences: 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.).


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 Potamopyrgus antipodarum are found here.

Full list of USGS occurrences

State/ProvinceFirst ObservedLast ObservedTotal HUCs with observations†HUCs with observations†
IL200620212Lake Michigan; Little Calumet-Galien
MI201220236Au Sable; Boardman-Charlevoix; Lake Erie; Lake Michigan; Manistee; Pere Marquette-White
MN200520202Lake Superior; St. Louis
NY199120164Lake Erie; Lake Ontario; Oak Orchard-Twelvemile; Seneca
OH200620191Lake Erie
PA200520232Chautauqua-Conneaut; Lake Erie
WI200520213Lake Michigan; Lake Superior; St. Louis

Table last updated 3/28/2024

† Populations may not be currently present.


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). Vazquez et al. (2016) demonstrated with field surveys and laboratory studies that P. antipodarum reproduction may be limited in low conductivity and environmental calcium waters.

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 (Dalton 2012). This snail is moved between streams and lakes by angler's or paddler's equipment (River Alliance of Wisconsin 2017; Richards et al. 2004). 

To prevent the spread of New Zealand mudsnails between adjacent waterbodies, it is recommended that gear be cleaned and disinfected after visiting a waterbody that may contain the snails, since accidental hitchhiking is one of the primary vectors for dispersal in the United States. Some effective ways of decontamination are outlined in detail by the Pennsylvania Fish and Boat Commission (see them here) and include:

  • Freezing gear for a minimum of six hours
  • Soaking gear in hot (>120 Fahrenheit) for at least five minutes
  • Soaking gear in a 1:1 solution of Formula 409 Degreaser Disinfectant and water



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). It is also established in all western states where it is found in the US.


Great Lakes Impacts:
Summary of species impacts derived from literature review. Click on an icon to find out more...

EnvironmentalSocioeconomicBeneficial



 

Potamopyrgus antipodarum has a moderate environmental impact in the Great Lakes.

Potential:
This species has a high reproductive capacity and a wide tolerance of abiotic conditions, increasing the potential for populations to grow and be widely-distributed (Alonso and Castro-Diez 2008). It is likely to find all shallower waters (<50 m depth) as suitable habitat (USEPA 2008). Potamopyrgus 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). Due to its ability to colonize empty spaces and habitats in early successional phases, P. antipodarum may also have greater invasion success in disturbed areas; however, its impacts are not limited to these types of systems (Alonso and Castro-Diez 2008).

Abundant populations of introduced P. antipodarum may outcompete other grazers for food resources and inhibit colonization by other macroinvertebrates and native snails (Kerans et al. 2005). Thus far, research efforts focused on interactions between P. antipodarum and native invertebrates have yielded mixed results, from commensalism to competition (Brenneis et al. 2010). In one Australian stream, increasing densities of P. antipodarum were positively correlated with density and species richness of native invertebrates, possibly due to coprophagy (ingestion of the snail's feces) (Schreiber et al. 2002). However, in Europe, P. antipodarum has caused declines in species richness and abundance of native snails in constructed ponds (Strzelec 2005).

A colonization experiment in Yellowstone National Park found a negative relationship between the abundance of P. antipodarum colonizers and native macroinvertebrate colonizers on stone tiles placed in several rivers, suggesting that P. antipodarum may interfere with the colonization activity of native species (Kerans et al. 2005). However, across sites, Kerans et al. (2005) did not find significant negative correlations between the densities of P. antipodarum and native macroinvertebrate densities, and overall impacts in this area remain largely unknown.

Brenneis et al. (2010) used field surveys, stable isotope analysis, and a laboratory experiment to analyze the extent of competition between P. antipodarum and native benthic invertebrates in the Columbia River Estuary. The authors found that while P. antipodarum was among one of the most abundant invertebrates, its abundance was also positively correlated with other native invertebrates (Brenneis et al. 2010). Stable isotope analysis indicated that the diet of P. antipodarum overlaps with the diets of coexisting invertebrates; however, the authors also found that P. antipodarum foraging was decreased in the presence of native Gnorimosphaeroma insulare, while foraging of G. insulare was unaffected by interspecific competition. Intraspecific competition had a stronger effect than interspecific competition for both species (Brenneis et al. 2010).

Cross et al. (2010) did not detect any impact on native species biomass following the invasion of P. antiodarum in Glen Canyon of the Colorado River. In contrast, field surveys below the Flaming Gorge Dam, documented an overall decrease in total invertebrate abundance following P. antipodarum invasion (Vinson et al. 2007). Interestingly, some invertebrate groups that were not affected by P. antipodarum overall were reduced in the presence of P. antipodarum in certain habitats (e.g., amphipods in eddies and mayflies in runs/riffles) (Vinson et al. 2007). In an enclosure competition experiment in Branbury Springs, ID, Richards (2004) found that resource-related competitive interactions likely have adverse effects on growth rates of a threatened native snail, Taylorconcha serpenticola, at P. antipodarum densities above 4,000 m-2. Riley et al. (2008) also found that P. antipodarum was a superior competitor to a native snail Pyrgulopsis robusta in Yellowstone National Park, documenting a negative correlation between their growth rates. Interestingly, analysis indicated that both species consumed similar amounts of algal resources, discrediting resource acquisition ability as a mechanism for interspecific competition. The authors suggest that adverse impacts on P. robusta could stem from lower maintenance costs or more efficient resource conversion within P. antipodarum (Riley et al. 2008).

Potamopyrgus antipodarum may have an impact on higher trophic levels of the food web. While P. antipodarum has been documented as a food source for Chinook salmon (Oncorhynchus tshawytscha; Bersine et al. 2008), brown trout (Salmo trutta; Vinson et al. 2007), and rainbow trout (Oncorhynchus mykiss), its lack of digestibility could be detrimental to its predators (Vinson and Baker 2008). Vinson and Baker (2008) found that 53.8% of New Zealand mudsnails passed through the digestive system of rainbow trout alive, with only 8.5% of snails estimated to have been fully digested. Furthermore, rainbow trout that were fed on a diet of P. antipodarum lost 0.14–0.48% of their initial weight per day. Unsuitability of P. anitopodarum as a food source and its potential competitive effects within lower trophic levels may affect food availability and alter food web processes in invaded systems (Kerans et al. 2005).

Potamopyrgus antipodarum is capable of serving as a host for a number of trematode parasites, although the extent of occurrence and consequences in its nonindigenous range is largely unknown (see Morley 2008).

A study by Arango et al. (2009) found that P. antipodarum altered periphyton community composition over a short time period by selective feeding. The study also suggested that by selectively grazing on non-nitrogen-fixing components of the algal assembly, P. antipodarum was able to increase nitrogen fixation in a high-productivity stream. In geothermal streams of the western U.S., P. antipodarum can reach densities of 300,000 snails/m2 and has been shown to alter nutrient (nitrogen and carbon) flows, consume a large portion of daily gross primary production (GPP), and account for most of the invertebrate production (Hall et al. 2003, Hall et al. 2006). For instance, Hall et al. (2006) found that P. antipodarum production accounted for 65–92% of invertebrate production within three geothermal streams. In one of these streams, the authors documented a biomass production rate of 194 gm-2 yr-1—among the greatest reported for any stream benthic invertebrates, and much higher than the observed production rate of natives (4.4-5.1 gm-2 yr-1) (Hall et al. 2006). Potamopyrgus antipodarum also appeared to play a large role in nitrogen cycling through extensive ammonium excretion (Hall et al. 2006). Although the authors suggest that P. antipodarum impact has been high in this area, comparably severe consequences are not yet widely reported, and may be partially attributed to this system’s particular hydrology, temperature, and productivity (Hall et al. 2006).

Current research on the socio-economic impact of Potamopyrgus antipodarum in the Great Lakes is inadequate to support proper assessment.

Potential:
Densities have reached 500,000 individuals per square meter in a Snake River tributary of Idaho (Richards et al. 2001); a species this prolific has potential to be a biofouler at facilities drawing from infested waters. Historically, P. antipodarum has both blocked and been distributed through water pipes in Australia (Ponder 1988).

If P. antipodarum has adverse impacts on food web interactions in invaded ecosystems (see above), it is possible that certain recreationally or commercially valuable species such as rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta) could be negatively impacted at high snail densities (NZMWG 2007).

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

Potential:
Partially due to their relatively high tolerance of environmental stressors, P. antipodarum is often used as a research organism to test novel experimental/analytical techniques (e.g., Myrick 2009, Schmitt et al. 2010a) or to test the physiological effects of toxic chemicals an aquatic fauna—particularly effects on the endocrine system (e.g., Alonso and Camargo 2009, Gust et al. 2009, Schmitt et al. 2010b)


Management: Regulations (pertaining to the Great Lakes region)

New Zealand mudsnails are listed as a prohibited species in Wisconsin (NR40.04: Prohibited), Minnesota (MN Administrative Rules, 6216.0250 Prohibited), Michigan (Michigan Invasive Species: Prohibited and Restricted) and New York (Regulatory Systems for Non-Native Species, Part 575).  Potamopyrgus antipodarum is prohibited in Ontario (regulatory amendments to Ontario Regulation 354/16 under the Invasive Species Act, 2015).

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

Control
Many times NZ mudsnails may be in a river or lake where chemical eradication will not be feasible and physical eradication difficult. Areas where eradication may be possible include small lakes and ponds, waterbodies that can be temporarily hydrologically separated. 

Biological
Parasites of NZ mudsnails from New Zealand may also become useful to control population size by inhibiting reproduction. Studies of the efficacy and specificity of a trematode parasite from the native range of NZ mudsnails as a biological control agent have shown positive results so far (Dybdahl et al. 2005).


Physical
New Zealand mudsnails easily hitchhike with fish and aquatic plants.  Inspection of boats/trailers/gear is essential, but equipment should also be dried thoroughly before moving from infected to uninfected waters.  Putting fishing gear in a freezer for 6-8 hours will kill all attached NZ mudsnails (Medhurst 2003, Richards 2004). Putting fishing gear in water maintained at 120°F for a few minutes will eliminate NZ mudsnails (Medhurst 2003). The mudsnails can survive at 110°F so the water temperature needs to be accurate. Dry fishing gear at 84-86°F for at least 24 hours or at 104°F for at least two hours (Richards et al. 2004).

For (aquaculture) facilities where no known NZ mudsnail contamination occurs, close visual inspection of water systems, raceways, stocking equipment, as well as regular gut content analysis can detect the arrival of snails before they can be spread. 

Physical treatments include the use of temperature, humidity or desiccation to kill the target species. This includes draining the infested areas. NZ mudsnails can survive for long periods in a cool damp environment; however, draining the areas where they are congregated and exposing them to sunlight during the summer months may be sufficient for eradication. Using a flamethrower in a hatchery situation against the walls of raceways will kill any mudsnails attached. Mudsnails cannot withstand warm temperatures (Dwyer et al. 2003; Richards et al. 2004) or low humidity situations (Dwyer and Kerans, unpublished; Richards et al. 2004). Alternately, if an infested area could be drained in the winter and the substrate is frozen to a depth containing the mudsnails, then total eradication will occur. There is preliminary evidence that hydrocyclonic separators may also be a useful tool to decontaminate fish hatchery water supplies and prevent the spread of NZ mudsnails within a hatchery.

Chemical
Chemical methods used to eradicate NZ mudsnails include: Bayer 73, copper sulfate, and 4-nitro-3-trifluoromethylphenol sodium salt (TFM). The only molluscicide known to have been tested against NZ mudsnails is Bayluscide (a.i. niclosamide). Preliminary investigations also suggest that copper and carbon dioxide under pressure may prove useful in both decontaminating fish hatchery water supplies and preventing spread into uncontaminated areas of a hatchery. Ozone has not been shown to be effective in killing NZ mudsnails in a hatchery environment.

The most effective solutions for killing NZ mudsnails which can be used in the field, according to this research are copper sulfate (252mg/L Cu), benzethonium chloride (1,940 mg/L) and 50% Commercial Solutions Formula 409® Cleaner Degreaser Disinfectant.

Copper sulfate, hyamine & hydrogen peroxide, have all been used to control New Zealand mud snails (IJC 2011). 

De Stasio et al (2019) found that total immersion in and spray treatments of 2% Virkon Aquatic were effective at killing mudsnails within 20 minutes. Formula 409 was also effective at killing mudsnails in both immersion and spray forms, but the presence of mud reduced its efficacy. The same study found that bleach was ineffective as a treatment for this species.

Other
It has been suggested that barriers such as copper stripping or electrical weirs may limit volitional movement of NZ mudsnails, particularly as a means of protecting high risk sites like fish hatchery water systems. Some investigations are underway but there is no applicable tool available yet.

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


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

Potamopyrgus antipodarum, in laboratory settings, has exhibited avoidance behaviors and the ability to detect and respond to novel piscine (fish) predators. This may be an important trait in the specie's invasion success (Levri et al. 2017). 

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.

In 2020, Potamopyrgus antipodarum were found in the Bluewater State Fish Hatchery in Montana, near Blues Creek, a tributary to the Clarks Fork Yellowstone River; decontamination of the facility occurred after discovery. In 2022, the snails were discovered again, and another decontamination procedure, including fish destruction, occurred, with an estimated cost of $225,000 UDS (NBC Montana Staff 2022)


References (click for full reference list)


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


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Revision Date: 11/1/2022


Citation for this information:
Benson, A.J., R.M. Kipp, J. Larson, and A. Fusaro, 2024, Potamopyrgus antipodarum (J.E. Gray, 1853): U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, and NOAA Great Lakes Aquatic Nonindigenous Species Information System, Ann Arbor, MI, https://nas.er.usgs.gov/queries/greatlakes/FactSheet.aspx?Species_ID=1008&Potential=N&Type=0&HUCNumber=DHuron, Revision Date: 11/1/2022, Access Date: 3/28/2024

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.