Kyle Cabana, age 12, of Richmond, Virginia, for his question:

 How does a starfish eat a clam?

Opening a stubborn clam with your bare hands is just about impossible. Yet the clam is a main dish on the menu of the starfish. Naturally a clam resents this and clamps his shells together with ail.his might. But all his might is not enough to resist the hungry starfish. In his own remarkable way he manages to pry the shells apart. And in his own very remarkable way he scoops up and digests the tender clam meat inside.

A starfish looks like a harmless little creature, but fishermen complain that he robs them of clams and raids their oyster beds. True, he seems rather helpless and slow. But he can move fast enough to catch a clam or an oyster, who never moves from his chosen location. These bivalves, or two shelled creatures, share the same tidal waters with their enemy the starfish, host of the time they keep their protective shells partly open to let in sea water, which serves them oxygen and morsels of food. But in times of trouble they close their shells and hold them tightly shut with strong hinges of muscular ligaments.

Trouble starts, for example, when a starfish selects a clam for his dinner. The undersides of the starfish's arms are fitted with rows of tiny tube feet. These are linked to an elaborate system of tubes inside his arms. This tubular network is an elaborate plumbing system that uses hydraulic power to exert tremendous pressure. The starfish can control his water power system to pull, to hold on, or to relax his grip. This is the built in tool he uses to aspen a stubborn clam.

First he humps himself onto the clam and attaches a few arms to each shell. His hydraulic system starts working and his little tube feet cling and begin to pull. The clam uses his muscular hinge to resist the pressure. But the crafty starf fish uses his numerous tube feet in relays to avoid fatigue. He can keep pulling indefinitely, but finally the clam's muscle grows weary, too weary to go on working. The hinge relaxes and the determined starfish pulls the shells apart.

Now comes an interesting problem. The starfish's mouth is in the center of his circle of arms and the small hole is much too small to engulf a clam. But the problem is solved by his most remarkable stomach. People and most animals must swallow their  food and send it down to the stomach to be digested. The starfish's stomach can turn inside out and poke itself through his small mouth. So, when the clam shells are parted, out pops this remarkable stomach and the starfish pokes it down into the juicy meat. There it partially digests the tender portions. This food is swallowed in morsels and sent to five digestive glands inside his arms for further treatment.

Starfish do, indeed, devour enormous numbers of clams and oysters. In the past, people caught starfish, chopped them in pieces and threw them back into the sea. This attempt to save the tasty shellfish failed because the starfish has a marvelous talent for rejuvenating himself. He can regrow one, two or more legs. When cut in half he often manages to regrow both pieces and become two hungry starfishes.