Freshwater Mussels


Kingdom - Animalia

Phylum - Mollusca (Snails, Slugs, Clams, Octopus, Squids, etc.)

Class - Bivalvia (Clams, oysters, mussels, etc.)

Order - Unionoida

Families in Illinois - Margaritiferidae (1 species) Unionidae (78 species historically)

Freshwater Mussels have:

  • two shell halves connected by a hinge and "teeth."
  • a shell composed of calcium carbonate secreted by mantle.
  • no head region or radula.
  • separate males and females.
  • a siphon through which they filter nutrients.
  • ctenidia (gills) for breathing and feeding.
  • a foot to dig into substrate or move along.
  • a larval stage (glochidia) that parasitize fish.




There are approximately 300 species of freshwater mussels in the United States.  Most species live in streams, spending their life at least partially burried in the sediment.  Freshwater mussels are often referred to as the "Livers of the Rivers" because they continuously filter water, removing detritus and plankton for food, and absorbing pollutants in their tissues. 

Approximately 70% of North American mussel species are imperiled due to overharvest, siltation, pollutions and competition from exotic species.  Some simple things you can do to help protect our streams and mussel populations:

  • maintain riparian (shoreline) vegetation to decrease erosion and absorb pollutants;
  • clean all gear used in our waterways to prevent the spread of exotic species like zebra mussels;
  • properly dispose of household chemicals and medicines to keep them out of the waterways.

The video below demonstrates the important function of freshwater mussels.

INHS researchers conduct surveys to update the status of our freshwater mussel populations and compare historic and current distributions.

INHS researchers are involved with re-establishing populations of the federally endangered Northern Riffleshell (Epioblasma rangiana) and the Clubshell (Pleurobema clava), in Illinois.

Their newest project involves the confirmation of two new exotic aquatic mollusks, Corbicula fluminea and Corbicula largillliertiCorbicula has been described as a “hyper-invasive alien.”

For more information on these and other projects, visit the Mollusk Collection website