Little knowledge of starfish

Starfish are star-like echinoderms belonging to the asteroid order. The common usage is that these names also apply to serpentines, which are correctly called brittle stars or "basket stars". From tropical to cold polar waters, there are about 1,500 species of starfish on the ocean floors of all the world's oceans. They range from the intertidal zone all the way to the deep sea and are found 6,000 meters (20,000 feet) below the surface. Starfish are marine invertebrates. They usually have a central disc and five arms, although some species have more arms. The oral or upper surface may be smooth, granular, or prickly, and covered with overlapping floors. Many species are brightly colored, with a variety of shades of red or orange, while others are blue, gray or brown. Starfish has pins operated by a hydraulic system and a mouth located in the center or lower surface of the mouth. They are opportunistic carnivores, predominantly predators of benthic invertebrates. Some species have specific feeding behaviors, including gastric valgus and suspension feeding. They have complex life cycles and can reproduce sexually and asexually. Most people can repair damaged parts or lost weapons, and they can shed weapons as a means of defense. The asteroid belt plays several important ecological roles. Starfish, such as ochre starfish (Pisaster ochraceus) and reef starfish (Stichaster australis), have become widely known as examples of key species concepts in ecology. The tropical crested crown starfish (Acanthaster planci) is a voracious predator of corals throughout the Indo-Pacific region, and the North Pacific starfish is considered one of the 100 worst invasive species in the world. The fossil record of starfish is old, dating back to the Ordovician period about 450 million years ago, but it is rather poor because starfish tend to disintegrate after death. Only the animal's small bones and vertebrae may have been preserved, which makes the remains difficult to find. With its fascinating symmetrical shapes, starfish have played an important role in literature, legend, design and popular culture. They are sometimes collected as antiques for design or as a logo, and in some cultures they are eaten despite being toxic.