Starfish typically eat mussels, clams and other bivalves. A starfish eats small fish, snails and barnacles by using its mouth, which is located on the underside of its body.
A starfish wraps its arms around a mussel shell or clam shell to pull it open, then it pushes its stomach through its mouth and into the shell. The starfish then digests the animal and moves its stomach back in place in its own body. The starfish is able to eat larger prey than it would otherwise be able to fit in its small mouth because of this unique method of digestion.