Starfish or sea stars are star-shaped echinoderms. Other common names for this fish are brittle stars or "basket stars". About 1,500 species of starfish live on the seabed in all the world's oceans, from the tropics to frigid polar waters. They are found from the intertidal zone down to abyssal depths, 6,000 m (20,000 ft) below the surface.
Starfish are marine invertebrates and they typically have a central disc and five arms, though some species have a larger number of arms. The aboral or upper surface may be smooth, granular or spiny, and is covered with overlapping plates. Many species are brightly colored in various shades of red or orange, while others are blue, grey or brown. Starfish have tube feet operated by a hydraulic system and a mouth at the center of the oral or lower surface. Most can regenerate damaged parts or lost arms and they can shed arms as a means of defence. The Asteroidea occupy several significant ecological roles.
Morning. It's morning, everyone! Today's the day! The sun is shining, the tank is clean, and we are gonna get out of... *gasps* The tank is clean!
Starfish, such as the ochre sea star and the reef sea star, have become widely known as examples of the keystone species concept in ecology. The tropical crown-of-thorns starfish is a voracious predator of coral throughout the Indo-Pacific region, and the northern Pacific sea star is considered to be one of the world's 100 worst invasive species.
The fossil record for starfish is ancient, dating back to the Ordovician around 450 million years ago, but it is rather poor, as starfish tend to disintegrate after death. Only the ossicles and spines of the animal are likely to be preserved, making remains hard to locate. With their appealing symmetrical shape, starfish have played a part in literature, legend, design and popular culture.