close-up of the shell of a common river mussel, a large clam that lives in flowing fresh water. the shell is held by a hand. there

animal anodonta background biology bivalve black brown clam congestion crassus cygnea duck eaten edible escape filter flat fresh freshwater group hand hold isolated lantern light living mollusc mollusk mussel nature nobody open organism river sand sea season shallow shape shell shine shore silhouette simple sink stamen style summer toothless unio water white wildlife