River snail
Viviparus viviparus
The river snail is a large freshwater snail with a conical shell and a horny operculum. It belongs to the Viviparidae family and is notable for being ovoviviparous, meaning it gives birth to live young. It is commonly found in slow-moving or stagnant waters with high oxygen levels, where it both grazes on algae and filters food from the water column.
Details
Identification
Dextral, thick-walled shell with 5-6 whorls; usually three dark brown bands on a yellowish-green base; circular operculum with concentric rings.
Social behavior
Peaceful and gregarious; often found in large groups on the water body floor or on aquatic plants.
Diet
Omnivore and filter feeder; feeds on algae, detritus, and organic suspended matter filtered from the water using its gills.
Hunting strategy
Passive filtering and active grazing of biofilms on stones and plants.
Spawning substrate
No substrate needed as they are ovoviviparous (development within the female's uterus).
Overwintering
Overwintering in the mud of the water body floor with a reduced metabolic rate.
Ecology
Ecological role
Important decomposer and filter feeder; contributes to the reduction of algae and the biological self-purification of water bodies.
Natural predators
Cyprinid fish, water birds (e.g., ducks), muskrats, and large predatory invertebrates.
Competitor species
Other large freshwater snails such as the great pond snail (Lymnaea stagnalis).
Ecosystem service
Water clarification through filtration; decomposition of organic waste; algae control.
Threats
Water pollution, excessive eutrophication, canalization of shores, and habitat loss.
Scientific profile
Profile
Distinguishing features
Key features include the blunt apex (shell tip) and moderately convex whorls without a deep suture (unlike V. contectus). The three dark bands are usually clearly visible. As a member of the Viviparidae, the species is dioecious and ovoviviparous (gives birth to live young). The presence of an operculum distinguishes it from pulmonate snails.
Diet
Detritus, phytoplankton, unicellular algae, and organic biofilm.
Reproduction
Ovoviviparous; fertilization is internal. Eggs develop within the female's uterus. Juveniles are born individually over several months (mostly summer), fully developed with a small shell.
Role in food web
Primary consumer and important link between benthic production and higher trophic levels.
Protection & threats
Main threats
River engineering, bank stabilization, excessive eutrophication (oxygen depletion at the bottom), and chemical pollution (pesticides).
Conservation measures
Preservation and restoration of near-natural bank structures and shallow water zones; reduction of nutrient inputs.