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.
Brittle stars, serpent stars, or ophiuroids are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their flexible arms for locomotion. The ophiuroids generally have five long, slender, whip-like arms which may reach up to 60 cm (24 in) in length on the largest specimens.
Mediaster aequalis is a species of sea star in the family Goniasteridae. It is native to the west coast of North America, ranging from Alaska to California. It is found in various habitats including beaches during very low tides, and at depths down to about 500 m (1,600 ft). Also known as the vermilion sea star, it is the type species of the genus Mediaster and was first described in 1857 by the American zoologist William Stimpson.
Solaster paxillatus, the orange sun star, is a species of starfish found at varying depths in the northern Pacific Ocean. It is a natural predator of the starfish Asterias amurensis.
Astropecten aranciacus, the red comb star, is a sea star of the family Astropectinidae. It is native to the east Atlantic Ocean and the Mediterranean Sea.
Ambulacral is a term typically used in the context of anatomical parts of the phylum Echinodermata or class Asteroidea and Edrioasteroidea. Echinoderms can have ambulacral parts that include ossicles, plates, spines, and suckers. For example, sea stars or "star fish" have an ambulacral groove on their oral side (underside). This ambulacral groove extends from the mouth to the end of each ray or arm. Each groove of each arm in turn has four rows of hollow tube feet that can be extended or withdrawn. Opposite the ambulacral groove is an ambulacral ridge on the aboral side of each ray, known as an ambulacrum. These have interambulacra between them.
Pisaster ochraceus, generally known as the purple sea star, ochre sea star, or ochre starfish, is a common seastar found among the waters of the Pacific Ocean. Identified as a keystone species, P. ochraceus is considered an important indicator for the health of the intertidal zone.
The Asterozoa are a subphylum in the phylum Echinodermata. Characteristics include a star-shaped body and radially divergent axes of symmetry. The subphylum includes the class Asteroidea, the class Ophiuroidea, and the extinct order Somasteroidea.
Astropecten spinulosus is a sea star of the family Astropectinidae.
Luidia clathrata is a tropical species of starfish in the family Luidiidae. It is variously known as the slender-armed starfish, the gray sea star, or the lined sea star. It is found in the western Atlantic Ocean.
Luidia senegalensis, the nine-armed sea star, is a tropical species of starfish in the family Luidiidae found in the western Atlantic Ocean.
Stylasterias is a genus of starfish in the family Asteriidae. Stylasterias forreri, the velcro star, is the only species in the genus. It is found on the Pacific coast of Canada and the United States.
Pteraster tesselatus, the slime star or cushion star, is a species of starfish in the family Pterasteridae found in the North Pacific.
Xyloplax medusiformis is a sea daisy, a member of an unusual group of marine taxa belonging to the phylum Echinodermata. It is found at bathyal depths in waters around New Zealand. It was first described in 1986 by Baker, Rowe and Clark and is the type taxon of the genus Xyloplax. Its generic name derives from the Greek "xylo" meaning wood and its specific name was chosen because its morphology superficially resembles that of a cnidarian medusa.
Ossicles are small calcareous elements embedded in the dermis of the body wall of echinoderms. They form part of the endoskeleton and provide rigidity and protection. They are found in different forms and arrangements in sea urchins, starfish, brittle stars, sea cucumbers, and crinoids. The ossicles and spines are the only parts of the animal likely to be fossilized after an echinoderm dies.
Poraniidae is a family of starfishes in the order Valvatida.
Poraniopsis inflata, the spiny sea star, is a species of starfish in the family Poraniidae. It is native to the Pacific Ocean and is found in deep water off the coast of North America.
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".
Astrostole scabra, commonly called the seven-armed starfish, is a sea star in the family Asteriidae, native to New Zealand, eastern Australia and southern Australia. A frequent inhabitant of the intertidal zone also seen attached to wharf piles, it is among the larger sea-stars found in New Zealand. Adults often prey on mussels, forcing the shells open by applying pressure for long periods with the tube feet.
The sun star (Heliaster helianthus) is a species of Asteroidea (starfish) in the family Heliasteridae. It is found in shallow water rocky habitats and in the kelp forests off the Pacific coast of Ecuador, Peru and Chile.
