Practical information to identify and manage non-native, invasive plants and animals
The Quiet Invasion:
A Guide to Invasive Species of the Galveston Bay Area
New Zealand mud snail
Potamopyrgus antipodarum

ITIS TSN:205006
Presence:Species of Concern
Habitat:Aquatic
Native Range:New Zealand
Human Health
This species poses no known human health impacts.
Prohibited Lists
As of 2010, this species is not prohibited by the TPWD.
Introduction Pathways
The New Zealand mud snail was introduced to the U.S. in the mid 1980s, possibly via ballast water from international shipping trade. The species can be spread by boat hull and trailer fouling and contaminated fishing gear. The snail can also be transported via fish and birds, due to its ability to survive digestion (ANSTF 2006).
Geographic Distribution
In the U.S. the New Zealand mud snail has populations in the freshwater systems of 15 states as well as 3 of the 5 Great Lakes. There are no known populations of P. antipodarum in Texas (Benson and Kipp 2009).
Specific Primary Habitats
The New Zealand mud snail occurs in both fresh and brackish waters in lakes, estuaries, ponds, rivers, ditches, reservoirs, and even water tanks. It exhibits tolerance to a wide range of environmental conditions including temperature, salinity, flow and substrate (silt, sand, mud, concrete, gravel, and cobble) (Crosier et al. 2006).  The mud snail can reach densities of up to 500,000 per square meter in western watersheds and 5,600 per square meter in the Great Lakes, with highest densities occurring from July to September. The mud snail lives among aquatic vegetation with silty, organic-rich substrate. The optimum salinity for growth is near or below 5 ppt, but it can tolerate salinities of 0-35 ppt and temperatures of 0-34°C (Benson and Kipp 2009).
Ecological, Economic, or Social Impact
The New Zealand mud snail is a prolific breeder. It may compete with native mollusks for food and habitat and can alter nutrient dynamics (ANSTF 2006; Benson and Kipp 2009).
Physical Description
The New Zealand mud snail has an average shell length of 4-5 mm. The shell is elongate, with 5-6 whorls, opens to the right, and the shell color is light to dark brown (Crosier et al. 2006).
Reproduction Characteristics
Mudsnail populations consist mostly of asexually reproducing females that are born with developing embryos in their reproductive system. All introduced populations in North America are clonal, consisting of genetically identical females (Benson and Kipp 2009). Females produce approximately 230 eggs per year, with reproduction occurring in spring and summer (ANSTF 2006).
Feeding
The New Zealand mud snail feeds nocturnally on plant and animal detritus, attached algae, sediment, and diatoms (Benson and Kipp 2009).
Control
Early detection is key to preventing the spread and establishment of this species and regional/local monitoring or surveillance is essential. Nonnative snails should not be imported alive or released in local waterways. If found in local waters, note the location and notify the TPWD. Due to the fact that this species can withstand short periods of desiccation and long periods with small amounts of moisture, decontamination of hiking gear and fishing and recreational boating equipment are necessary to prevent the spread to new waterways. There are international shipping regulations in effect for this species (ANSTF 2006).

This species belongs to the following lists:
Images
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New Zealand mud snails <i>(Potamopyrgus antipodarum)</i>.  Photo courtesy of Mike Gangloff, USGS NAS Database, http://nas.er.usgs.gov.
New Zealand mud snails (Potamopyrgus antipodarum).  Photo courtesy of Mike Gangloff, USGS NAS Database, http://nas.er.usgs.gov.
New Zealand mud snails <i>(Potamopyrgus antipodarum)</i>.  Photo courtesy of Justin Morrison, USGS NAS Database, http://nas.er.usgs.gov.
New Zealand mud snails (Potamopyrgus antipodarum).  Photo courtesy of Justin Morrison, USGS NAS Database, http://nas.er.usgs.gov.
New Zealand mud snails <i>(Potamopyrgus antipodarum)</i>.  Photo courtesy of USGS, Southeast Ecological Science Center.
New Zealand mud snails (Potamopyrgus antipodarum).  Photo courtesy of USGS, Southeast Ecological Science Center.
Page Updated/Reviewed: 09/07/2010 10:20 AM
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