Taxonomic name: Potamopyrgus antipodarum (Gray, 1843)
Synonyms: Hydrobia jenkinsi (Smith, 1889), Potamopyrgus jenkinsi (Smith, 1889)
Common names: Jenkin's spire shell, New Zealand mudsnail
Organism type: mollusc Potamopyrgus antipodarum is an aquatic snail native to New Zealand and introduced to Australia, Europe, and North America. It can inhabit a wide range of ecosystems, including rivers, reservoirs, lakes, and estuaries. P. antipodarum can comprise over 95% of the invertebrate biomass in a river and it is suspected that it can alter primary production in some streams. They can spread rapidly in introduced areas and are able to withstand desiccation, a variety of temperature regimes, and are small enough that many types of water users could be the source of introduction to new areas. Description
Potamopyrgus antipodarum is a small, aquatic snail. Richards et al. (2002) state that the operculum is like all prosobranchs but that P. antipodarum "has an operculum to block the shell aperture when the animal is withdrawn into its shell. This is easily seen on live snails, but the operculum is lost from dead shells and it is normally withdrawn beyond view in shells that are directly preserved in alcohol or formalin." The authors also state that "the shell is normally horn coloured but ranges from light to dark brown. Encrusted shells can be any colour. Almost all western populations reach a maximal size very near 5mm. One population in Idaho (Cassia Creek of the Raft River) regularly pushes 6mm. The shell is rather elongate compared to most western species. Like most snails, it is dextral (opening to the animal's right). A full-grown shell normally has 5 or 6 whorls, which is higher than most western species. In some western populations, a weak keel is present about mid whorl in some to most individuals. Many populations lack this keel entirely. This keel is not present on any native western snail species." Occurs in:
estuarine habitats, lakes, water courses Habitat description
Richards et al. (2002) state that Potamopyrgus antipodarum has "a wide range of tolerances: rivers, reservoirs, lakes, and estuaries. Densities are usually highest in systems with high primary productivity, constant temperatures, and constant flow." In rivers it is found in all habitat substrates; silt, sand, gravel, cobbles, and vegetation (Richards et al. 2001, In Richards et al. 2002). In estuaries P. antipodarum can tolerate up to 17-24% salinity (Bondesen and Kaiser 1949, in Richards et al. 2002). Mud snails are able to withstand desiccation and a variety of temperature regimes (National Park Service, Undated). General impacts
USGS-FISC (Undated) states that Potamopyrgus antipodarum "densities of over one-half million per metre square in western streams are a cause for concern. Because the West is known for abundant trout and productive fishing spots, there is concern that P. antipodarum will impact the food chain for native trout and the physical characteristics of the streams themselves." Richards et al. (2002) report that "frequently, P. antipodarum will comprise over 95% of the invertebrate biomass in a river. To date, limited research has documented decreases in native macroinvertebrate populations in several rivers where P. antipodarum has invaded. P. antipodarum has also been shown to drastically alter primary production in some streams. Its invasion has generated much concern about the potential impacts it may have on native species, fisheries, and aquatic ecosystems in the western USA." The National Park Service (Undated) states that "these small molluscs have the potential to 'cover the stream bottom,' similar to impacts observed with the Zebra Mussel (Dreissena polymorpha) in the midwestern U.S. Preliminary baseline surveys indicate that P. antipodarum may be impacting the invertebrate community in the Madison, Firehole, and Gibbon rivers not only through physical displacement or crowding, but also through competitive interactions such as food availability. These streams not only support world famous recreational fisheries, but they also historically contained an abundance of native aquatic insects that form an important part of the aquatic food chain. Reductions in the insect species diversity or abundance could diminish the availability of this critical food resource to fish. Mud snails are a poor substitute for the traditional food base, yielding as little as 2% of their nutritional value when eaten by trout." Notes
Lively (Undated) reports that "genetic studies have shown that asexual lines are derived from sympatric sexual females and that clonal diversity in mixed populations is very high (Dybdahl & Lively 1995, in Lively, Undated). Geographical range
Native range: New Zealand (USGS-FISC, Undated).
Known introduced range: Europe, Australia, and North America (USGS-FISC, Undated) Introduction pathways to new locations
Ignorant possession: The National Park Service (Undated) states that "the rapid spread of P. antipodarum throughout the Madison River watershed may have been assisted by human transport. Mud snails are able to withstand desiccation, a variety of temperature regimes, and are small enough that many types of water users (anglers, swimmers, picnickers, pets) could inadvertently be the mechanism for interbasin transfer of this nuisance species."
Seafreight (container/bulk): JNCC (2002) states that P. antipodarum "was introduced in drinking water barrels in ships from Australia (Ponder 1988, in JNCC, 2002). The snails were probably liberated while washing or filling water barrels or tanks and, because they can survive in brackish water, they could probably survive liberation into estuarine areas such as the River Thames."
Local dispersal methods
Hikers' clothes/boots: The National Park Service (Undated) states that "the rapid spread of P. antipodarum throughout the Madison River watershed may have been assisted by human transport. Mud snails are able to withstand desiccation, a variety of temperature regimes, and are small enough that many types of water users (anglers, swimmers, picnickers, pets) could inadvertently be the mechanism for interbasin transfer of this nuisance species." Management information
Preventative measures: Expanding US National Park Service efforts to increase public awareness of potential threats to existing aquatic communities may be one of the best tools for containing P. antipodarum.
Physical: The National Park Service (Undated) states that "there are few effective treatments to completely eliminate P. antipodarum." The authors go on to state that "attempts at crushing or physical removal of the snails may only exacerbate the problem by spreading eggs to new sites."
Chemical: Chemical treatment would not necessarily be selective for snails only and could eliminate remnant invertebrate populations. Nutrition
Richards et al. (2002) state that Potamopyrgus antipodarum is "classified as a scraper/grazer. It prefers diatoms, plant and animal detritus, and attached periphyton." Reproduction
Richards et al. (2002) states that Potamopyrgus antipodarum “ranges from 20-120 embryos per female.” The authors go on to state that young are born every three months in New Zealand (Winterbourn 1970, in Richards et al. 2002) but that they can bear young at any time of year in spring habitats in the Western United States (Richards unpublished data, in Richards et al. 2002), but overall they will bear young in the summer and autumn. Lively (Undated) reports that "most populations of this gastropod consist solely of triploid parthenogenetic females, but many populations also contain diploid, sexual females and males.” Lifecycle stages
Richards et al. (2002) report that the lifespan of P. antipodarum has been observed at over a year in several marked individuals. Its growth rate depends on size. Richards et al. (2002) report that P. antipodarum "can grow 0.1mm/day at 21 degrees C under laboratory conditions. The author also states that "in western USA P. antipodarum reaches sexual maturity at 3.0mm." Reviewed by: Dr Sabine Schreiber, Arthur Rylah Institute for Environmental Research Department of Sustainability and Environment. Australia
Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
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Last Modified: Wednesday, 26 January 2005
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