Commercial clam and oyster fishermen have stiff competition--sea stars. Sea stars have a huge appetite for clams and oysters. When a sea star uses its two arms to grip a clam or oyster, it doesn't have strong muscles to rip the shell open. Instead, the sea star shows great patience. Eventually, the clam or oyster relaxes its muscle that keeps the shell closed. Then, the sea star easily opens the shell and eats the meat. Back in the day, whenever a fisherman found sea stars among their clam or oyster nets, the fishermen would cut the sea stars in half and throw the pieces back into the ocean. What fishermen didn't know was that sea stars could regenerate their missing body parts. So if a fisherman cut up fifty sea stars, one hundred regenerated sea stars would be formed, giving fishermen even more competition! Sounds like science fiction? Actually, regeneration is just one of the amazing features of animals belonging to phylum echinodermata, the spiny skinned invertebrates.