How do echinoderms move and get their food?

For the sea star, they grap a clam with all five arms, then it pulls on the tightly closed shell with its tube feet. When the shell opens, the sea star forces its stomach out through its mouth and into the opening between the clam's shells. And then the digestive chemicals break down the clam's tissues, and the star sucks in the partially digested body of its prey.