The freshwater mussel has an outer shell consisting of two halves held together by a dorsal elastic hinge. This hinge permits the valves to open and close, allowing the clam's foot and siphons to protrude. In defense, the clam will pull in its muscular foot and siphons and lock itself tightly shut.
Freshwater mussels have no head, eyes, or appendages.
The insides consist of a mass of muscle, soft tissue, intestinal tract, and reproductive organs. A clam feeds by siphoning water through its internal digestive tract, where food such as zooplankton and algae are filtered out and digested. Clams don't get around much and are usually found in colonies called beds. They often bury themselves in the mud or sand bottoms of streams, with only their back ends exposed. This provides protection while allowing the siphons to bring in food, water, and oxygen.