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Montana Animal Field Guide

Montana Field Guides

New Zealand Mudsnail - Potamopyrgus antipodarum

Exotic Species (not native to Montana)

Global Rank: G5
State Rank: SNA
* (see State Rank Reason below)

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State Rank Reason (see State Rank above)
Not ranked, as this is an exotic species to Montana.
General Description
This is an introduced species to MT with an expanding distribution in the Missouri, Madison, Yellowstone, and Bighorn Rivers. It is not known in Montana west of the continental divide. In Montana this species was first discovered in the Madison River above Hebgen Reservoir in 1995 (Gustafson 2001). However, the very large population present at that time indicataes that the introduction was a few years earlier. It is a native of New Zealand, but long established in Australia and Europe. This species has been known in North America since 1987 in the Snake River basin of Idaho

Diagnostic Characteristics
Taxonomically, New Zealand mud snails are in the snail family Hydrobiidae. Hydrobiids can be distinguished from other aquatic snail families by having dextral (opening to the right with the spire pointing away from you) shells with an operculum (a hard calcareous flat that can seal the opening of the shell). New Zealand mud snails are small (~ 1-2 mm) and generally dark colored

Range Comments
Native to New Zealand. Introduced to Europe in the 1800's where it is now widespread. Introduced into the Snake River system (Idaho) in North America (first appeared in 1987) and is now present in the Great Lakes and Madison and Missouri rivers (Howells 1999). Since then it has spread to nearly a dozen sites in Lake Ontario (Zaranko et al., 1997). Kerans et al. (2005) list it from Idaho, Great Lakes, California, Wyoming and Montana.

Summary of Observations Submitted for Montana
Number of Observations: 5

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(Observations spanning multiple months or years are excluded from time charts)

New Zealand mud snails appear to prefer flowing water habitats with stable flows. Springs, spring creeks, and river sections downstream from dams are all places that they thrive in. They are most typically found on larger cobble substrates or on pieces of wood.

Reproductive Characteristics
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.

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Citation for data on this website:
New Zealand Mudsnail — Potamopyrgus antipodarum.  Montana Field Guide.  .  Retrieved on , from