It is native to
New Zealand, where it is found throughout the country.[3] However, it has been introduced to many other countries. It is often considered an
invasive species because populations of the snail can reach very high densities.
Shell description
The
shell of Potamopyrgus antipodarum is elongated and has dextral coiling, with 7 to 8
whorls. Between whorls are deep grooves. Shell colors vary from gray and dark brown to light brown. The average height of the shell is approximately 5 mm ( in); maximum size is approximately 12 mm ( in). The snail is usually 4–6 mm in length in the
Great Lakes, but grows to 12 mm in its native range.[4][5][6] It is an
operculate snail, with a 'lid' that can seal the opening of its shell. 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.[4][7][5][6]
Taxonomy
This species was originally described as Amnicola antipodarum in 1843 by
John Edward Gray:
Inhabits New Zealand, in fresh water. Shell ovate, acute, subperforated (generally covered with a black earthy coat); whorls rather rounded, mouth ovate, axis 3 lines; operculum horny and subspiral: variety, spire rather longer, whorls more rounded. This species is like Paludina nigra of Quoy and Gaimard, but the operculum is more spiral. Quoy described the operculum as concentric, but figured it subspiral. Paludina ventricosa of Quoy is evidently a Nematura.[2]
Forms
Potamopyrgus antipodarum f. carinata (J. T. Marshall, 1889)
Distribution
This species was originally
endemic to
New Zealand where it lives in freshwater streams and lakes in New Zealand and adjacent small islands.[8]
It has now spread widely and has become
naturalised, and an invasive species in many areas including: Europe (since 1859 in England), Australia (including Tasmania), Asia (Japan[9] and Iraq[10]), and North America (USA and Canada[11][9]), most likely due to inadvertent human intervention.
Invasion in Europe
Since being found in London as early as 1859, Potamopyrgus antipodarum has now spread to nearly the whole of Europe. It is considered as about the 42nd worst alien species in Europe and the second worst alien gastropod in Europe.[12]
It does not occur in Iceland, Albania or the former Yugoslavia.[13]
First detected in the
United States in
Idaho's
Snake River in 1987, the mudsnail has since spread to the
Madison River,
Firehole River, and other watercourses around
Yellowstone National Park; samples have been discovered throughout the western United States.[6] Although the exact means of transmission is unknown, it is likely that it was introduced in water transferred with live
game fish and has been spread by
ship ballast or contaminated recreational equipment such as wading gear.[20]
The New Zealand mudsnail has no natural predators or parasites in the United States, and consequently has become an invasive species. Densities have reached greater than 300,000 individuals per m2 in the Madison River. It can reach concentrations greater than 500,000 per m2, endangering the
food chain by outcompeting native snails and water insects for food, leading to sharp declines in native populations.[21] Fish populations then suffer because the native snails and insects are their main food source.
Mudsnails are impressively resilient. A snail can live for 24 hours without water. They can however survive for up to 50 days on a damp surface,[22] giving them ample time to be transferred from one body of water to another on fishing gear. The snails may even survive passing through the digestive systems of fish and birds.[23]
Mudsnails have now spread from Idaho to most western states of the U.S., including
Wyoming,
California,
Nevada,
Oregon,
Montana, and
Colorado. Environmental officials for these states have attempted to slow the spread of the snail by advising the public to keep an eye out for the snails, and bleach or heat any gear which may contain mudsnails. Rivers have also been temporarily closed to fishing to avoid anglers spreading the snails.[24][25]
The snails grow to a smaller size in the U.S. than in their native habitat, reaching 6 mm (1⁄4 in) at most in parts of Idaho, but can be much smaller making them easy to overlook when cleaning fishing gear.
Clonal species like the New Zealand mudsnail can often develop clonal lines with quite diverse appearances, called
morphs. Until 2005, all the snails found in the western states of the U.S. were believed to be from a single line. However a second morph has been identified in Idaho's Snake River. It grows to a similar size but has a distinctive appearance. (It has been nicknamed the salt-and-pepper mudsnail due to the final whorl being lighter than the rest of the shell.) This morph has apparently been present in the area for several years before being identified correctly as a distinct morph of Potamopyrgus antipodarum. It dominates the typical morph where they overlap, and has a much higher prevalence of males.[26]
In 1991, the New Zealand mudsnail was discovered in
Lake Ontario,[27] and has now been found in four of the five
Great Lakes. In 2005 and 2006, it was found to be widespread in Lake Erie.[28] By 2006 it had spread to
Duluth-Superior Harbour and the freshwater estuary of the
Saint Louis River.[29] It was found to be inhabiting
Lake Michigan, after scientists took water
samples in early summer of 2008.[30] The snails in the Great Lakes represent a different line from those found in western states, and were probably introduced indirectly through Europe.[26]
In 2002, the New Zealand mudsnail was discovered in the Columbia River Estuary. In 2009, the species was discovered in
Capitol Lake in Olympia, Washington. The lake has been closed to all public use, including boating and other recreation, since 2009.[31] A heavy cold snap in 2013, combined with a drawdown in water level in preparation, was roughly estimated to have killed 40–60% of the mudsnail population.[32][33] Other known locations include the Long Beach peninsula, Kelsey Creek (King County), Thornton Creek (King County), and
Lake Washington.
In 2010, the Los Angeles Times reported that the New Zealand mudsnail had infested watersheds in the
Santa Monica Mountains, posing serious threats to native species and complicating efforts to improve stream-water quality for the endangered Southern California
Distinct Population Segment of
steelhead.[34] According to the article, the snails have expanded "from the first confirmed sample in Medea Creek in
Agoura Hills to nearly 30 other stream sites in four years." Researchers at the Santa Monica Bay Restoration Commission believe that the snails' expansion may have been expedited after the mollusks traveled from stream to stream on the gear of contractors and volunteers.[35]
As of 21 September 2010[update] In Colorado, Boulder Creek and Dry Creek have infestations of New Zealand mudsnails. The snails have been present in Boulder Creek since 2004 and were discovered in Dry Creek in September 2010. Access to both creeks has been closed to help avoid spread of the snails. In the summer of 2015 an industrial-scale wetland rehabilitation project was undertaken in northeast Boulder to rid the area of a mud snail infestation.[citation needed]
Ecology
Habitat
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.[4][6][36][37][38][39][40][41][42][43][44]
In the Great Lakes, the snail reaches densities as high as 5,600 per m2 and is found at depths of 4–45 m on a silt and sand substrate.[4][5][6]
This species is
euryhaline, establishing populations in fresh and
brackish water. The optimal
salinity is probably near or below 5
ppt, but Potamopyrgus 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.[4][6][45][46][47][48]
Potamopyrgus antipodarum is
ovoviviparous and
parthenogenic. This means that they can reproduce
asexually; females "are born with developing embryos in their reproductive system". 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.[6]
As the snails can reproduce both sexually and asexually, the snail has been used as a model organism for studying the costs and benefits of sexual reproduction. Asexual reproduction allows all members of a population to produce offspring and avoids the costs involved in finding mates. However, asexual offspring are
clonal, so lack variation. This makes them susceptible to parasites, as the entire clonal population has the same resistance mechanisms. Once a strain of parasite has overcome these mechanisms, it is able to infect any member of the population. Sexual reproduction mixes up resistance genes through
crossing over and the random assortment of gametes in
meiosis, meaning the members of a sexual population will all have subtly different combinations of resistance genes. This variation in resistance genes means no one parasite strain is able to sweep through the whole population. New Zealand mudsnails are commonly infected with
trematode parasites, which are particularly abundant in shallow water, but scarce in deeper water. As predicted, sexual reproduction dominates in shallow water, due to its advantages in parasite resistance. Asexual reproduction is dominant in the deeper water of lakes, as the scarcity of parasites means that the advantages of resistance are outweighed by the costs of sexual reproduction.[54]
Each female can produce between 20 and 120
embryos.[20] The snail produces approximately 230 young per year. Reproduction occurs in spring and summer, and the life cycle is annual.[4][6][8][48][55][56] The rapid reproduction rate of the snail has caused the numbers of individuals to increase rapidly in new environments. The highest concentration of New Zealand mudsnails ever reported was in
Lake Zurich,
Switzerland, where the species colonized the entire lake within seven years to a density of 800,000 per m2.[6][57]
Parasites
The parasites of this species include at least 11 species of Trematoda.[6][58] Common parasites of this snail include trematodes of the genus Microphallus.[6][59][60]
In their native habitat, these parasites sterilize many snails, keeping the populations to a manageable size. However, elsewhere in the world in the absence of these parasites, they have become an invasive pest species.[6]
Other interspecific relationships
Potamopyrgus antipodarum can survive passage through the
guts of fish and birds and may be transported by these animals.[23]
It can also float by itself or on mats of Cladophora spp., and move 60 m upstream in 3 months through positive rheotactic behavior.[4] 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.[6][61]
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^Holomuzki, J. R. and B. J. F. Biggs. 2006. Habitat–specific variation and performance trade–offs in shell armature of New Zealand mudsnails. Ecology 87(4):1038–1047.
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abHall, 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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abAamio, K. and E. Bornsdorff. 1997. Passing the gut of juvenile flounder Platichthys flesus (L.) – differential survival of zoobenthic prey species. Marine Biology 129: 11–14.
^"Non-native snail turns up in Truckee River". Elko Daily Free Press. 20 May 2013. p. 4.
^Collier, K. J., R. J. Wilcock and A. S. Meredith. 1998. Influence of substrate type and physico–chemical conditions on macroinvertebrate faunas and biotic indices in some lowland Waikato, New Zealand, streams. New Zealand Journal of Marine and Freshwater Research 32(1):1–19.
^Holomuzki, J. R. and B. J. F. Biggs. 1999. Distributional responses to flow disturbance by a stream–dwelling snail. Oikos 87(1):36–47.
^Holomuzki, J. R. and B. J. F. Biggs. 2000. Taxon–specific responses to high–flow disturbances in streams: implications for population persistence. Journal of the North American Benthological Society 19(4):670–679.
^Negovetic, S. and J. Jokela. 2000. Food choice behaviour may promote habitat specificity in mixed populations of clonal and sexual Potamopyrgus antipodarum. Experimental Ecology 60(4):435–441.
^Richards, D. C., L. D. Cazier and G. T. Lester. 2001. Spatial distribution of three snail species, including the invader Potamopyrgus antipodarum, in a freshwater spring. Western North American Naturalist 61(3):375–380.
^Weatherhead, M. A. and M. R. James. 2001. Distribution of macroinvertebrates in relation to physical and biological variables in the littoral zone of nine New Zealand lakes.
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^Schreiber, E. S. G., G. P. Quinn and P. S. Lake. 2003. Distribution of an alien aquatic snail in relation to flow variability, human activities and water quality. Freshwater Biology 48(6):951–961.
^Suren, A. M. 2005. Effects of deposited sediment on patch selection by two grazing stream invertebrates.
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^Jacobsen, R. and V. E. Forbes. 1997. Clonal variation in life–history traits and feeding rates in the gastropod, Potamopyrgus antipodarum: performance across a salinity gradient. Functional Ecology 11(2):260–267.
^Leppäkoski, E. and S. Olenin. 2000. Non–native species and rates of spread: lessons from the brackish Baltic Sea. Biological Invasions 2(2):151–163.
^Costil, K., G.B. J. Dussart and J. Daquzan. 2001. Biodiversity of aquatic gastropods in the Mont St–Michel basin (France) in relation to salinity and drying of habitats. Biodiversity and Conservation 10(1):1–18.
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^Cox, T. J. and J. C. Rutherford. 2000. Thermal tolerances of two stream invertebrates exposed to diurnally varying temperature. New Zealand Journal of Marine and Freshwater Research 34(2):203–208.
^Broekhuizen, N., S. Parkyn and D. Miller. 2001. Fine sediment effects on feeding and growth in the invertebrate grazer Potamopyrgus antipodarum (Gastropoda, Hydrobiidae) and Deleatidium sp. (Ephemeroptera, Letpophlebiidae).
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^James, M. R., I. Hawes and M. Weatherhead. 2000. Removal of settled sediments and periphyton from macrophytes by grazing invertebrates in the littoral zone of a large oligotrophic lake. Freshwater Biology 44(2):311–326.
^Kelly, D. J. and I. Hawes. 2005. Effects of invasive macrophytes on littoral–zone productivity and foodweb dynamics in a New Zealand high–country lake. Journal of the North American Benthological Society 24(2):300–320.
^Parkyn, S. M., J. M. Quinn, T. J. Cox and N. Broekhuizen. 2005. Pathways of N and C uptake and transfer in stream food webs: an isotope enrichment experiment. Journal of the North American Benthological Society 24(4):955–975.
^Fox J., Dybdahl M., Jokela J., Lively C. (1996). Genetic structure of coexisting sexual and clonal subpopulations in a freshwater snail (Potamopyrgus antipodarum). Evolution. 50 (4): 1541-1548
^Schreiber, E. S. G., A. Glaister, G. P. Quinn and P. S. Lake. 1998. Life history and population dynamics of the exotic snail Potamopyrgus antipodarum (Prosobranchia: Hydrobiidae) in Lake Purrumbete, Victoria, Australia. Marine and Freshwater Research 49(1):73–78.
^Lively, C. M. and J. Jokela. 2002. Temporal and spatial distribution of parasites and sex in a freshwater snail. Evolutionary Ecology Research 4(2):219–226.
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Further reading
Kerans, B. L, M. F. Dybdahl, M. M. Gangloff and J. E. Jannot. 2005. Potamopyrgus antipodarum: distribution, density, and effects on native macroinvertebrate assemblages in the Greater Yellowstone ecosystem. Journal of the North American Benthological Society 24(1):123–138.
Strzelec, M. 2005. Impact of the introduced Potamopyrgus antipodarum (Gastropods) on the snail fauna in post–industrial ponds in Poland. Biologia (Bratislava) 60(2):159–163.
de Kluijver, M. J.; Ingalsuo, S. S.; de Bruyne, R. H. (2000). Macrobenthos of the North Sea [CD-ROM]: 1. Keys to Mollusca and Brachiopoda. World Biodiversity Database CD-ROM Series. Expert Center for Taxonomic Identification (ETI): Amsterdam, the Netherlands.
ISBN3-540-14706-3. 1 cd-rom.