Starfish (Asteroidea) are a group of animals belonging to the echinoderms. Starfish have a star-shaped body with a central disc and usually five lobes elongate arms which can be mentioned. The central body bracket includes the stomach, with the mouth opening at the bottom. In the event that the species has a anus, which is located on the upper side. The appearance is a species apart. So known species with several dozen poor and there are many besides the brown-gray also red, blue and yellow starfish species. Some species have spines, others a smooth body surface. At the bottom of the arms are tubular feet with sticky pans. In addition, each arm accommodates parts of the gastro-intestinal tract and genital organs. Starfish couples do not just put their gametes off in the seawater. Some species have a form of parental care. The larvae of starfish are free swimming and look like translucent shrimp-like creatures. The larvae go through several stages before they turn into a small starfish. In starfish can regenerate lost or damaged parts of the body. They are predators and some types can consume a lot of clams in a short time. Starfish are found worldwide, tidal waters into the deep sea, but only in salt water. The best known species in Belgium and the Netherlands is the common starfish (Asterias rubens), which can reach a diameter of up to 50 centimeters. Starfish are approximately 1900 species of one of the largest groups of echinoderms. There are many extinct species known. Sea stars are often found alive on the beach and in tidal pools.