A starfish isn’t actually a fish at all. Fish have a backbone. Starfish have exoskeletons (from the Greek exo which means “outside” and from the Latin skeletos meaning “dried out”) like crabs and insects. There are about two thousands kinds of starfish (also called sea stars) living in all the oceans in the World.
Starfish are only live only in saltwater; there are no freshwater sea stars anywhere in the world.
The kind we see most often is the five armed type, however there are some that will have as many as forty arms. Most sea stars are about 8 inches across, but some are as large as a small automobile. Most sea stars also have an incredible way to eat. A starfish has 2 stomachs. A sea star eats by pushing one of its stomachs outside of its body. Using tiny, suction-cupped tube feet, they open clams or oysters, and their stomach emerges from their mouth (in the center of the starfish) and oozes inside the shell of its victim. The stomach then surrounds its dinner and digests it while it is inside the shell of its victim. Then the stomach returns back into the body of the sea star and this stomach dumps its contents into the sea star’s second stomach.
Starfish breathe through their feet and have little tiny breathing tubes all over their bodies. They have no eyes, but have instead a small eyespot on the end of their arms, so they can tell if it is light or dark. Sea stars are famous for being able to regrow their arms. In some cases their entire bodies can be regrown from just a bit of an arm. This can happen because sea stars have most of their vital organs only in their arms. Sea stars do not have a brain.
Most starfish live for three to five years. Sea stars have been on Earth for about 40 million years.
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