An Introduction to Starfish (1/3)

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Starfish (2007-09-03 11-18-09a)

Starfish are aquatic, oceanic animals, but they are not fish. Instead they belong to the phylum Echinodermata, a word which comes from the Greek meaning “skin like a hedgehog” which, due to their rough, protective skin, is extremely appropriate.

There are between 1,500 and 2,000 species of starfish in the world depending on which expert you ask. All live in salt water but they can be found at a variety of depths ranging from tide pools to 20,000 feet (roughly 6,000 meters.) They are found in a wide variety of temperatures as well, ranging from tropical to frigid waters. They also come in a wide range of sizes as well. The smallest measure about half an inch while the largest reach about four feet in diameter.

Starfish are the most easily recognizable marine invertebrates (animals which do not possess a backbone). As the name implies, they look like stars with five “arms” extending from a central hub. Some starfish actually have more than five arms, as many as forty or fifty, but the number is almost always a multiple of five. The exception to the rule is the Seven-armed Starfish (Luidia ciliaris) which, as the name implies, has seven arms. Starfish occasionally loose arms but they can regrow a missing one. Sometime a regrowing arm will split and one arm will be replaced by two.

Written by Gary J Sibio

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