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Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea (/ ˌ æ s t ə ˈ r ɔɪ d i ə /). Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or basket stars. Starfish are also known as asteroids due to being in the class
Heliaster kubiniji is a species of starfish in the order Forcipulatida. It is commonly known as the gulf sun star , the common sun star or estrella de mar de golfo and it occurs in the intertidal zone of the Pacific coast of California, Mexico and Nicaragua.
If attacked by a predator such as the morning sun star (Solaster dawsoni) or the sunflower star (Pycnopodia helianthoides), the slime star emits great quantities of repellent mucus and can often evade the predator. [3] The mucus is toxic and has been shown to kill other invertebrates immersed in it. [3]
That is, the internal organs of digestion and reproduction never enter the arms, as they do in the Asteroidea. The underside of the disk contains the mouth, which has five toothed jaws formed from skeletal plates. The madreporite is usually located within one of the jaw plates, and not on the upper side of the animal as it is in starfish. [5]
Ambush predation is widely distributed in the animal kingdom, spanning some members of numerous groups such as the starfish, cephalopods, crustaceans, spiders, insects such as mantises, and vertebrates such as many snakes and fishes.
Asterias amurensis, also known as the Northern Pacific seastar and Japanese common starfish, is a seastar found in shallow seas and estuaries, native to the coasts of northern China, Korea, far eastern Russia, Japan, Alaska, the Aleutian Islands and British Columbia in Canada.
Like other starfish in the family Asteriidae, Marthasterias glacialis is a predator and feeds mostly on bivalve molluscs and other invertebrates. [6] It has been found that secondary metabolites known as saponins , found within the starfish's tissues, have a dramatic effect on the whelk Buccinum undatum .
Aboral surface of an Asterias forbesi sea star showing ring of pedicellariae surrounding spine. Asterias, like most starfish genera in the order Forcipulatida, are recognisable externally by their pedicellariae, many thousands of tiny jaw-like structures on the skin which can snap shut to nip at prey or predators.