Mussels are filter feeders that filter microscopic aquatic life, such as plankton, from the water around them. The larvae of some mussel species are temporarily parasitic.
Mussels are bivalves, like clams and oysters, that live in both saltwater and freshwater habitats. A mussel feeds by filtering water through the body. Water enters through the incurrent syphon organ and moves through the body via the motion of cilia. Wastewater exits the mussel's body through the excurrent syphon. Food filters out of the water, and labial palps pass it to the mussel's mouth. A mussel's food typically consists of phytoplankton, zooplankton and algae.
The larvae of certain freshwater mussels spend a portion of their lives as a sort of parasite, living on the gills of a host fish. This does not typically harm a fish unless the larval load is extremely high.
Mussels are important indicators of the health of a waterway. Mussels also keep waterways clean of excess plankton and algae and may even filter out some harmful bacteria.
Zebra mussels are a mussel species native to eastern Europe that is invasive in many North American waterways. Like other mussels, zebra mussels are filter feeders. They inhabit waterways in numbers so great that their populations are capable of filtering the entire contents of some lakes and ponds in a single day, robbing native aquatic species of sustenance.