Freshwater mussels live burrowed in muck and sand. They are known as filter feeders because they feed by drawing in water through their siphons and filtering out suspended particles and algae. In doing so they improve the quality and the clarity of the water. Additionally they are a valuable food source for many mammals. Though mussels are generally sedentary, they can move slowly in the bottom substrate with their foot. When they are disturbed they will withdraw into their shell and hold it tightly closed.
Pictured above is a fresh water mussel that clamped its shell on a fishing lure that had touched it.
Female mussels reproduce by taking in sperm released by males to fertilize their eggs. The eggs develop into free swimming larvae call Glochidia which parasitize fish by encysting themselves on the gills or fins of their host. The larvae will use the fish as transportation for 1 to 4 weeks until it drops off to become an adult. Generally this is not terribly harmful to the fish but it can be if too many Glochidia encyst themselves. Many freshwater mussels are very specific about the species of fish they will parasitize and will not be successful in reproducing if that particular species is not present.