New Zealand Mudsnails
Category
Invasive Gastropod (Family Hydrobiidae) — operculate snail
Common Name
New Zealand Mudsnail
Species Name
Potamopyrgus antipodarum
Distribution / Status (Tahoe)
Established invasive; first detected in 2023 near the Tahoe Keys; as of 2025, distributed over about 4 km of the south shore littoral zone
Diagnostic Features
Tiny, right-coiling, hard shell with operculum and 5–9 whorls, operculum present
Commonly Confused Species
Sinistral Pond Snail / Bladder Snail (Physidae)
Shell Shape / Form
5–9 whorls, dextral (right-coiling); elongate-conical, pointed spire
Shell Size
4–6 mm long (adults mature ≈ 3 mm)
Shell Thickness
Thick for size; hard, calcified
Aperture
Oval, small, with complete lip edge
Shell Sculpture / Texture
Smooth, fine growth lines only
Color / Patterning
Light to dark brown or black
Operculum covering aperture
Present (horny, circular)
Soft Body Features
Small pale foot; distinct operculum on posterior foot end
Habitat Type
Benthic zones of streams and lakes; prefers cool, well-oxygenated waters but tolerates wide conditions including eutrophic habitats.
Substrate Preference
Can be found in most any substrate
Depth Range
4–50 m; benthic and on macrophytes
Temperature Range
0–33 °C (optimal 10–25 °C); intolerant of freezing
Association / Behavior
Free-living benthic grazer; non-burrowing. Crawls on sediment, rocks, and vegetation; often clings tightly to substrates and forms dense aggregations on hard surfaces.
Ecological Role / Impact
Invasive — forms dense colonies (>75,000 m⁻²); outcompetes natives; indigestible to fish; scrapes algae, detritus, and diatoms
Reproduction
Parthenogenetic females; up to 230 young per year
References
California Department of Fish and Wildlife. (n.d.). California’s Invaders: New Zealand Mudsnail. California Department of Fish and Wildlife. Retrieved from https://wildlife.ca.gov/Conservation/Invasives/Species/NZmudsnail
Hoddle, M. (n.d.). New Zealand Mud Snail. University of California Riverside Center for Invasive Species Research. Retrieved from https://cisr.ucr.edu/invasive-species/new-zealand-mud-snail
Smithsonian Environmental Research Center. (n.d.). Species summary: Potamopyrgus antipodarum (New Zealand mudsnail). National Exotic Marine and Estuarine Species Information System (NEMESIS). Retrieved October 28, 2025, from https://invasions.si.edu/nemesis/species_summary/205006
U.S. Department of Agriculture, National Invasive Species Information Center. (n.d.). New Zealand mud snail (Potamopyrgus antipodarum). U.S. Department of Agriculture. Retrieved from https://www.invasivespeciesinfo.gov/aquatic/invertebrates/new-zealand-mud-snail
Supporting Partners
The Martis Fund, a collaborative project of Martis Camp landowners, DMB/Highlands Group (the developers of Martis Camp), Mountain Area Preservation (MAP), and Sierra Watch. (See martisfund.org for more information)
The Community Impact Fund, Ashley Quinn Fund & the Foresight Fund held at the Tahoe Community Foundation
Additional thanks to the Tahoe Regional Planning Agency for providing specimens for studio filming
