Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea. 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 Asteroidea. About 1,900 species of starfish live on the seabed in all the world's oceans, from warm, tropical zones to frigid, polar regions. They are found from the intertidal zone down to abyssal depths, at 6,000 m (20,000 ft) below the surface.
Asterias is a genus of the Asteriidae family of sea stars. It includes several of the best-known species of sea stars, including the (Atlantic) common starfish, Asterias rubens, and the northern Pacific seastar, Asterias amurensis. The genus contains a total of eight species in all. All species have five arms and are native to shallow oceanic areas of cold to temperate parts of the Holarctic. These starfish have planktonic larvae. Asterias amurensis is an invasive species in Australia and can in some years become a pest in the Japanese mariculture industry.
The Valvatida are an order of starfish in the class Asteroidea, which contains 695 species in 172 genera in 17 families.
The Echinasteridae are a family of starfish in the monotypic order Spinulosida. The family includes eight genera and about 133 species found on the seabed in various habitats around the world.
The Asterinidae are a large family of sea stars in the order Valvatida.
Goniasteridae constitute the largest family of sea stars, included in the order Valvatida. They are mostly deep-dwelling species, but the family also include several colorful shallow tropical species.
The Brisingids are deep-sea-dwelling starfish in the order Brisingida.
Leptasterias is a genus of starfish in the family Asteriidae. Members of this genus are characterised by having six arms although five-armed specimens sometimes occur. L. muelleri is the type species. The taxonomy of the genus is confusing and Leptasterias hexactis seems to be a species complex. Some species brood their eggs.
Hippasteria is one of 70 genera of sea stars in the diverse family Goniasteridae.
Poraniidae is a family of starfishes in the order Valvatida.
The Freyellidae are a family of deep-sea-dwelling starfish. It is one of two families in the order Brisingida. The majority of species in this family are found in Antarctic waters and near Australia. Other species have been found near New Zealand and the United States.
Astropecten latespinosus is a species of starfish in the family Astropectinidae. It is one of the commonest starfish in the seas around Japan. The name in Japanese is hira momiji, "hira" meaning flattened and "momiji" meaning maple leaves tinged with bright red, a name given to certain starfish which resemble maple leaves in form.
Trophodiscus almus is a species of starfish in the family Astropectinidae. It is found in fairly deep waters in the Sea of Okhotsk, the Sea of Japan and around the Japanese island of Hokkaido. It is very unusual among starfish in that it broods its young on its upper surface. Its common name in Japanese is "Komochi-momiji".
Pterasteridae is a family of sea stars in the order Velatida, consisting of eight genera.
Bathyporania ascendens is a species of starfish in the family Poraniidae, and the only species of the genus Bathyporania. It is native to the Pacific Ocean and is found in deep water off the coast of North America.
Clavaporania fitchorum is a species of starfish in the family Poraniidae. It is the only known species of the genus Clavaporania. It is native to the South Pacific Ocean and is found in deep water off the coast of Australia.
Evoplosoma is a genus of deep-sea sea star in the family Goniasteridae.
Astroceramus is a genus of abyssal sea stars in the family Goniasteridae.
Apollonaster is a genus of abyssal sea stars in the family Goniasteridae. They can be identified by their bare abactinal plate surfaces and multiple accessory granule rows on their abactinal plates. To date, Apollonaster has been found in the tropical Atlantic region and Hawaiian Islands region oceans, with no other locations or species being known as of 2015.
Euretaster insignis, commonly known as the striking sea star, is a species of starfish in the family Pterasteridae found in the central west Pacific Ocean. It is one of only three species in the order Velatida to be found in shallow water in the tropics. The young are brooded in a cavity underneath a "supradorsal" membrane.
