Crown of Thorns Starfish

Topics: Coral, Coral reef, Great Barrier Reef Pages: 3 (1127 words) Published: May 2, 2007
Starfish or sea stars are marine invertebrates belonging to the phylum Echinodermata; class Asteroidea. Crown of Thorns Starfish (Acanthaster planci) are found on coral reefs in the tropics ranging from the Red Sea, the Indian and Pacific Oceans, and all the way to the Pacific coast of Panama. It plays a major role in the destruction of fast growing coral species. Scientists believe that this starfish has lived on the reefs for tens of thousands of years and when the populations of this echinoderm increase in number, they can seriously damage the coral reefs. The Crown of Thorns Starfish has 16 to 18 arms and are covered all over with thousands of long, venomous spines. The spines are extremely sharp and are known to have a toxic reaction in humans. This is also the largest starfish in the world. Their size is usually 10 to 13 inches cm in diameter, but some can grow to 80 cm depending on availability of food and living conditions. It can be dull greyish green with pale tinges of red or a bright blue or purple. Their life expectancy is not certain but Crown of Thorns Starfish have lived up to 8 years in an aquarium. Crown of Thorns Starfish eat coral. Not the coral skeletons, just the delicate coral polyps. Coral flesh is just a thin film on the outside of the coral skeleton and the polyps can withdraw down into protective little cups, so coral is not very easy to make a meal out of. A hungry starfish climbs up on a coral and pulls its stomach out of its mouth with its tube feet. The starfish has thousands of these flexible tube feet, each ending with a little suction cup. The feet pass the stomach from one to the next until the big yellow stomach is spread out over the coral. Then the stomach expels digestive juices over the live coral to dissolve it. The cells of the stomach scoff up the bits of dissolving coral. When the starfish has cleaned the coral right to the white calcium carbonate skeleton, it sucks in its stomach and moves off, using its tube feet....
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