Swan mussel
Anodonta cygnea
The swan mussel is one of the largest native freshwater mussels, reaching shell lengths of up to 20 centimeters. Its shell is thin-walled, oval-shaped, and usually yellowish to brownish in color, lacking hinge teeth. It prefers standing or slow-moving waters with muddy or sandy substrates. As a filter feeder, it plays an important role in the ecosystem by cleaning the water of suspended particles and serving as a host for the spawning of the European bitterling.
Details
Identification
Very thin shell, no hinge teeth present, umbo located before the center of the shell, usually yellow-brown coloration.
Social behavior
Usually lives gregariously in larger populations on the water bottom, but shows no active social behavior.
Diet
Actively filters plankton, bacteria, and fine organic detritus particles from the water column.
Hunting strategy
Passive suspension feeder by filtering the respiratory water.
Spawning substrate
The larvae (glochidia) require the gills of fish as a temporary developmental substrate.
Overwintering
Overwinters buried deep in the sediment with a significantly reduced metabolism.
Ecology
Ecological role
Important water filterer; provides the European bitterling (Rhodeus amarus) with protection for its eggs (symbiosis).
Natural predators
Muskrats, Eurasian otters, raccoons, and large predatory fish (for juvenile mussels).
Competitor species
Zebra mussel (Dreissena polymorpha), which can suffocate swan mussels by growing on their shells.
Ecosystem service
Biofiltration to reduce turbidity, nutrient cycling, and sediment stabilization.
Threats
Water pollution, predation by muskrats, loss of host fish, and habitat destruction through bank reinforcement.
Scientific profile
Profile
Distinguishing features
The most important feature is the toothless hinge (no cardinal or lateral teeth). Compared to the Duck Mussel (Anodonta anatina), the shell of A. cygnea is significantly larger, thinner, and the dorsal margin is almost parallel to the ventral margin. The umbonal rugae consist of fine, concentric lines that are not wavy.
Diet
Phytoplankton, bacteria, organic detritus, and fine suspended particles.
Reproduction
Brood care within the gill lamellae (marsupium). The larvae (glochidia) are released in spring and must live parasitically on the gills or fins of fish (e.g., stickleback, perch) for their development.
Role in food web
Important primary consumer; acts as a biological water filter and links pelagic primary production with the benthos (benthic-pelagic coupling).
Protection & threats
Main threats
River engineering, eutrophication (oxygen depletion at the bottom), loss of suitable host fish, predation by muskrats, and competition from invasive species like the zebra mussel (Dreissena polymorpha).
Conservation measures
Protection and promotion of host fish populations, reduction of nutrient inputs to prevent excessive siltation, preservation of natural shoreline structures.