David Purcell, Age 11, of Allentown, Pa., for his question:
How does a starfish eat?
He looks like a petaled flower and some of his relatives are called sea lilies and sea cucumbers. However, all these sea dwellers ors animals, though none of them are classed among the fishes. The starfish, who looks so delicate, is really a sturdy little character. He can open an oyster with his bare fingers, which is more than you can do.
If you have ever tried, you know how hard it is to open a stubborn oyster. The starfish is very fond of oysters and his tapering arms use the suction power of water to pry apart the shells. He begins by humping over his victim with his arms fixed firmly to each shell. Then he pulls and pulls the shells apart with a steady pressure.
The oyster tries to resist, but after a while he must yield and his shells come apart. The starfish gets ready for dinner. His main body is a disk in the center of his radiating arms. It houses a hollow stomach and on the under side is a little round mouth. The starfish pushes part of his stomach through his mouth and of all things, sends it down inside the oyster.
This amazing traveling stomach digests the tender oyster meat right where it is, between the shells. When dinner is finished, the stomach goes back home. The starfish eats marine worms and other mushy morsels but his favorite foods are oysters and clams.
His tapering arms look far too fragile to open an oyster, but the fob is done by geritle hydraulic pressure, a method of using the suction power of water. On the top of his disk, he has a seive plate to let in the water to operate the tubes and suckers of his hydraulic system.
Hundreds of tiny suckers cover the under side of each of the starfish's arms. They are the ends of his tube feet. These elastic tubes stretch when filled with water and shrink when the water is withdrawn. When filled with water, the tubes press the suckers tight against a hard surface. This tough grip, controlled by water pressure. Enables the starfish to outpull a determined Oyster.
One tube foot cannot exert much pressure, but the starfish has hundreds of them. He uses his suckers in relays, some rest while others work. This enables him to exert a steady pressure without tiring. The Oyster has only one wad. Of Muscle to hold his shells together and after a while it must relax. When this happens, his shells come apart and the stomach of the starfish dips down to dine.