When the mussels feels it s in danger, the foot is quickly retracted within the shell to protect itself from predators. The mussel reproductive system is very unique, because the juvenile stage is parasitic on fish. Larva called glochidium attatch themselves to the gills and the fins of a fish host. The fish s tissue reacts by growing around the glochidia. After several weeks, the parasitic larval form is released and develop into free-living clams.
Mussels use gills like fishes to breathe underwater.
The water taken in through the siphons for food passes through their gills to deliver the oxygen mussels need to survive. The gills are thin plate-like structures that remove the oxygen that is dissolved in the water. A mussel can be identified by it s outer shell. Mussels shells within the same species closely resemble one anothers. Thus, by examining the mussel s shell, you can identify what type of mussel it is.