Keeled ramshorn snail
Planorbis carinatus
The keeled ramshorn snail is a medium-sized freshwater air-breathing snail in the family Planorbidae. Its shell is flat and disc-shaped, featuring a characteristic keel that runs almost exactly in the middle of the whorls. It prefers to inhabit plant-rich, stagnant, or slow-moving waters such as ponds, ditches, and lakes. The species is widespread across Europe and feeds primarily on algae and detritus.
Details
Identification
Flat, disc-shaped shell; keel is located centrally on the whorl (distinction from P. planorbis); shell diameter up to 20 mm; 4.5 to 5 whorls.
Social behavior
Solitary, but often occurs in high densities when food supply is abundant.
Diet
Feeds as a grazer on algal films (periphyton), detritus, and decaying aquatic plants.
Spawning substrate
Smooth surfaces such as aquatic plants, stones, or submerged leaf litter.
Overwintering
Overwintering in sediment or on aquatic plants in deeper, frost-free water zones.
Ecology
Ecological role
Important decomposer and algae grazer in the aquatic ecosystem; contributes to the nutrient cycle.
Natural predators
Fish (e.g., tench, carp), waterfowl, dragonfly larvae, and leeches.
Competitor species
Other planorbids such as Planorbis planorbis or Anisus species.
Ecosystem service
Supports the self-purification of water bodies by breaking down organic matter.
Threats
Loss of habitat through drainage of wetlands and intensive water body maintenance.
Scientific profile
Profile
Distinguishing features
Characteristic is the sharp keel located exactly in the middle of the whorl periphery (medial). Unlike Planorbis planorbis, where the keel is at the lower edge, it is central in P. carinatus. Furthermore, the whorls in P. carinatus expand much more rapidly than in related species.
Diet
Algal periphyton, detritus, and decaying plant material (diatoms, green algae).
Reproduction
Hermaphroditic; eggs are laid in flat, gelatinous capsules, usually attached to the underside of aquatic plant leaves.
Role in food web
Primary consumer; converts plant biomass and detritus into animal biomass and serves as important prey for higher trophic levels.
Protection & threats
Main threats
Habitat loss through drainage of wetlands, intensive water body maintenance (weed removal), excessive eutrophication, and herbicide use.
Conservation measures
Preservation and restoration of near-natural standing waters and oxbow lakes; avoidance of radical weed removal; protection of riparian vegetation.