The New Zealand mud snail (Potamopyrgus antipodarum) is a species of very small freshwater snail with a gill and an operculum. This aquatic gastropod mollusk is in the family Tateidae.
It is native to New Zealand, where it is found throughout the country. 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. 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.Zaranko, D. T., D. G. Farara and F. G. Thompson. 1997. Another exotic mollusk in the Laurentian Great Lakes: the New Zealand native Potamopyrgus antipodarum (Gray 1843) (Gastropoda, Hydrobiidae).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.Levri, E.P., A.A. Kelly and E. Love. 2007. The invasive New Zealand mud snail (Potamopyrgus antipodarum) in Lake Erie. Journal of Great Lakes Research 33: 1–6.
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.
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.
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 (JapanTimothy M. Davidson, Valance E. F. Brenneis, Catherine de Rivera, Robyn Draheim & Graham E. Gillespie. Northern range expansion and coastal occurrences of the New Zealand mud snail Potamopyrgus antipodarum (Gray, 1843) in the northeast Pacific Aquatic Invasions (2008) Volume 3, Issue 3: 349-353. and IraqMurtada D. Naser & Mikhail O. Son. 2009. First record of the New Zealand mud snail Potamopyrgus antipodarum (Gray 1843) from Iraq: the start of expansion to Western Asia? . Aquatic Invasions, Volume 4, Issue 2: 369-372, DOI 10.3391/ai.2009.4.2.11.), and North America (USA and Canada), 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.
It does not occur in Iceland, Albania or the former Yugoslavia.Mikhail O. Son. Rapid expansion of the New Zealand mud snail Potamopyrgus antipodarum (Gray, 1843) in the Azov-Black Sea Region . Aquatic Invasions (2008) Volume 3, Issue 3: 335-340.
Countries where it is found include: Great Britain since 1859 Ireland Germany Poland Western Baltic Sea since 1887Dmitry P. Filippenko & Mikhail O. Son. The New Zealand mud snail Potamopyrgus antipodarum (Gray, 1843) is colonising the artificial lakes of Kaliningrad City, Russia (Baltic Sea Coast) . Aquatic Invasions (2008) Volume 3, Issue 3: 345-347. Russia Azov Black Sea region, since 1951, Ukraine since 1951 in brackish waters, and since 2005 in freshwaterBoris Alexandrov, Alexandr Boltachev, Taras Kharchenko, Artiom Lyashenko, Mikhail Son, Piotr Tsarenko & Valeriy Zhukinsky. Trends of aquatic alien species invasions in Ukraine . Aquatic Invasions (2007) Volume 2, Issue 3: 215-242. Catalonia in Spain, since 1952 Mediterranean region of France, since the end of 1950s Italy, since 1961 Turkey Czech Republic, since September 3, 1981Kuchař P. Potamopyrgus jenkinsi poprvé v Československu. Źiva, Prague, 31(1): page 23. (in Czech). Slovakia, since 1986Čejka T., Dvořák L. & Košel V. 2008: Present distribution of Potamopyrgus antipodarum (Gray, 1843) (Mollusca: Gastropoda) in the Slovak Republic. - Malacologica Bohemoslovaca, 7: 21-25. Online serial at <http://mollusca.sav.sk> ; 25-February-2008. Greece, since November 2007Canella Radea, Ioanna Louvrou and Athena Economou-Amilli First record of the New Zealand mud snail Potamopyrgus antipodarum J.E. Gray 1843 (Mollusca: Hydrobiidae) in Greece – Notes on its population structure and associated microalgae . Aquatic Invasions (2008) Volume 3, Issue 3: 341-344
Distribution within the United States
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. 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.
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. 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, 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.
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 freeze or heat any gear which may contain mudsnails. Rivers have also been temporarily closed to fishing to avoid anglers spreading the snails.
The snails grow to a smaller size in the U.S. than in their native habitat, reaching 6 mm ( 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.
In 1991, the New Zealand mudsnail was discovered in Lake Ontario, 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.New Zealand Mud Snails Invade Lake Erie!, International Association for Great Lakes Research, 26 March 2007. By 2006 it had spread to Duluth-Superior Harbour and the freshwater estuary of the Saint Louis River. It was found to be inhabiting Lake Michigan, after scientists took water samples in early summer of 2008. The snails in the Great Lakes represent a different line from those found in western states, and were probably introduced indirectly through Europe.
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. 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. 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. 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.
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.
Ecology
Habitat