New Zealand mud snail
Potamopyrgus antipodarum
The New Zealand mud snail is a highly adaptable, small snail species originally native to New Zealand. It has spread globally as an invasive species in freshwater and brackish water ecosystems. Particularly notable is its ability for parthenogenetic reproduction, allowing a single female to establish an entire population. It often colonizes the bottom of water bodies in massive numbers and can displace native species.
Details
Identification
Shell dextral with 5 to 6 whorls, operculum present, color varies from horn-colored to dark brown.
Social behavior
Solitary, but occurs in extreme densities of up to 500,000 individuals per square meter.
Diet
Grazes on algae, diatoms, and organic detritus from hard substrates and aquatic plants.
Spawning substrate
No substrate required as the species is live-bearing (ovoviviparous).
Overwintering
Overwintering in sediment; shows some tolerance to low temperatures but sensitive to freezing.
Ecology
Ecological role
Primary consumer; can dominate nutrient cycling in high densities and displace native mollusks.
Natural predators
Some fish species and waterfowl; however, many predators cannot digest the snail due to its hard shell.
Competitor species
Native freshwater snails such as Theodoxus fluviatilis or Radix balthica.
Ecosystem service
Low; decomposition of organic material, but mostly negative impacts on biodiversity.
Threats
No significant threats; spread usually occurs passively through fishing and shipping.
Scientific profile
Profile
Distinguishing features
Characterized by the presence of an operculum and a slender, high-spired shell. In Europe, populations consist almost entirely of females reproducing parthenogenetically. A key feature is ovoviviparity: fully developed juveniles or embryos are often visible within the mother's brood pouch. Some individuals may exhibit a keel or bristles on the shell whorls.
Diet
Primarily periphyton (biofilm of algae and bacteria), diatoms, and organic detritus.
Reproduction
In invasive ranges, reproduction is almost exclusively parthenogenetic. The species is ovoviviparous (live-bearing); embryos develop within the female's brood pouch and are released as fully formed juveniles.
Role in food web
Primary consumer; in mass occurrences (up to 500,000 ind./m²), it can dominate nutrient dynamics and displace native species through exploitative competition.
Protection & threats
Main threats
None; the species is extremely adaptable and is considered highly invasive in Europe and North America.
Conservation measures
No conservation measures required. Management focuses on preventing spread (equipment cleaning, 'Clean-Drain-Dry').