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There are over 2,000 species of starfish found in all the seas. Most of these are found in shallow water, but a few do live in the deep seas. They appear to be most numerous in the northern part of the North Pacific.
The typical body is made up of five arms that radiate from a small central body with a toothless mouth on the underside. The number of arms may vary greatly, as well as the size, from species to species.
The colors of the starfish range from yellow, orange, pink, and red, with a few that are gray, blue, green, or purple.
Plates covered with a thin layer of skin support the body wall of the starfish. Spines also project from the surface singly or in a group. Muscles at their base move each spine. The surface may have little pincer-like jaws mounted on a short stalk on three spines that are positioned close together. They are important in preventing the surface of the starfish from becoming encrusted with algae or other small organisms.
Starfish move by numerous tube feet arranged in rows along the underside of each arm. The muscles of the tube feet propel the starfish along in the water. At the tips of the feet are suction discs, which help secure the starfish to a rock or to its prey.
A starfish has very good regenerative powers and can easily grow back an arm or two if it has lost them. Starfish are carnivorous and feed on fish, crustaceans, worms, and mollusks. There is one species that feeds on coral polyps.
The female starfish releases millions of eggs into the sea. A larva hatches from the egg and from the larva, in about two months time, a young starfish will break free. This is just a very simplified version for one species. There are other species of the starfish that are totally different in their development.
Starfish can be found on most beaches. These starfish are usually dead or dying. They are very popular to collect and are used in decorations.
Asteroidea Phanerozonia • Archaster typicus
Length: 1/2 inch to 3 feet across (1 cm–0.9 m)
Special Design Feature: The starfish can lose one or more of its arms and still survive, and the lost arms will regenerate.
Did You Know? The starfish typically have 5 arms, but there have been some reported with up to 50 arms.