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Archive - July 2018

What are Mussels?
Mussels are invertebrate animals. They are members of the Phylum Mollusca, commonly known as mollusks. A mussel has a soft body surrounded by a hard, outer shell. There are two parts to the shell (bivalve), a left side and a right side. A ligament holds the two pieces together at the hinge. The soft body tissues include the mantle that secretes the shell, the foot that is used for movement and muscles that open and close the shell. Gills are present and have several functions. They are used for exchanging carbon dioxide and oxygen with the water that the mussel lives in.

They strain food particles from water. They are also the place where mussel larvae live and feed. Siphons move water into and out of the shell.

What Do They Look Like? 
There are many types of mussels so there are many different sizes, shapes and colors of them. Mussel species can be identified by their shell characteristics.

How Big are They?
Mussel species found in Illinois range from the smallest at about one inch in length to the largest at about eight inches long.

Where Do They Live?
Mussels live in water. Most species live in rivers and streams where the water moves. Other mussel species can be found in ponds and lakes. Different types of mussels may have specific habitats that they need. Many mussel species require clean water with little or no silt. Mature mussels live partially or entirely buried on the bottom of their water body in mud, gravel or sand.

How Do They Reproduce?
Usually, mussels are either male or female, but some are hermaphrodites (have both male and female reproductive organs in the body). When they are ready to reproduce, the males release their sperm into the water. If the sperm are drawn into the body of a female of the same species, they may fertilize her eggs. Fertilized eggs develop into larvae (glochidia) that start their life living on the female’s gills. When larvae are mature, the female releases them into the water where they must find and attach to the fins or gills of a fish. They are parasites of the fish and must stay there for weeks or months as they develop their adult structures. When they can live on their own, they drop to the bottom of the water body.

What Do They Eat?
They filter food items from the water. Their food includes pieces of dead plants and animals as well as microscopic plants and animals.

What Else Should I Know About Them?

  • If conditions are good, mussels can live for 10-100 years.
  • Mussel shells were once used to make buttons for clothing.
  • Pieces of freshwater mussel shells are used to form the nucleus of cultured pearls produced from oysters.
  • There are 80 species of mussels native to Illinois. More than half of them are endangered, threatened, extirpated or extinct.
  • Mussels are very sensitive to changes in the environment. Mussel populations have been declining due to habitat loss, siltation, pollution and competition from exotic species.

Can I Catch and Keep Them?
Persons possessing a sport fishing license may possess up to 50 relic mussel shells for a personal collection. Restrictions may apply due to property rules and the fact that many mussel species are endangered or threatened. Never take live mussels.

Teacher Resources and Additional Information