- Published: 05 May 2008
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Erin Marie Salisbury, age 7, of Eugene, Ore., for her question:
HOW IS A STARFISH BORN?
Female starfish release lots of tiny eggs into the sea through small holes between their arms. The eggs form into tiny swimming larvae. After a while, each larva settles down on the sea bottom and develops into a starfish.
Starfish can also regenerate. If you cut a starfish into two, each of the pieces will regenerate into a new animal. If one were to lose an arm, a new one will grow to replace the one that has been broken off.
Starfish live in all of the world's oceans. But they are not fish. They belong to a group of animals called echinoderms. Included in the echinoderm group are sea cucumbers, sea lillies and sea urchins.
Most starfish have five armlike extensions that give them somewhat the look of a five pointed star. One type, called the sun star, has many arms that make the creature resemble the sun and its rays.
A starfish has a mouth in the central disk of its body, on the underside. It leads directly into a large, baglike stomach. On the outside of the body, a groove extends from the mouth to the tip of each earm. Rows of slender tubes, called tube feet, line these grooves. The animal uses the suction disk at the end of each tube foot for crawling.
A starfish's disks can grip hard surfaces. It can easily cling to rocks.
Small colored eyespots are located at the tip of each arm which give the starfish an ability to "see." The starfish cannot actually form images but it can sense light.
The starfish uses its tube feet and a tiny, sensitive tentacle located at the tip of each arm to "feel."
Starfish feed on shelled animals such as mussels, clams and oysters. The starfish can push his stomach out through his mouth. When he feeds on an oyster, he attaches his tube feet to the two halves of the oyster's shell and pulls the shell halves apart, opening a crack between them.
After the starfish has opened the halves of an oyster's shell, he will push his stomach into the opening. Before doing this, the starfish turns his stomach inside out. He can push his stomach through a crack no larger than the thickness of a piece of cardboard.
Then the starfish's stomach surrounds the oyster's soft body, and slowly digests it, absorbing the food into his own body.
As you can imagine, the starfish is considered a pest in oyster breeding grounds of the eastern coast of the United States. Some starfish have no arms at all. They are simply shaped like pentagons.