An echinoderm is any member of the phylum Echinodermata of marine animals. The adults are recognizable by their radial symmetry, and include starfish, sea urchins, sand dollars, and sea cucumbers, as well as the sea lilies or "stone lilies". Adult echinoderms are found on the sea bed at every ocean depth, from the intertidal zone to the abyssal zone. The phylum contains about 7000 living species, making it the second-largest grouping of deuterostomes, after the chordates. Echinoderms are the largest phylum that has no freshwater or terrestrial members.
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 1,500 species of starfish occur on the seabed in all the world's oceans, from the tropics to frigid polar waters. They are found from the intertidal zone down to abyssal depths, 6,000 m (20,000 ft) below the surface.
The crown-of-thorns starfish, Acanthaster planci, is a large starfish that preys upon hard, or stony, coral polyps (Scleractinia). The crown-of-thorns starfish receives its name from venomous thorn-like spines that cover its upper surface, resembling the biblical crown of thorns. It is one of the largest starfish in the world.
Linckia laevigata is a species of sea star in the shallow waters of tropical Indo-Pacific.
The Ophidiasteridae are a family of sea stars with about 30 genera. Occurring both in the Indo-Pacific and Atlantic Oceans, ophidiasterids are greatest in diversity in the Indo-Pacific. Many of the genera in this family exhibit brilliant colors and patterns, which sometimes can be attributed to aposematism and crypsis to protect themselves from predators. Some ophidiasterids possess remarkable powers of regeneration, enabling them to either reproduce asexually or to survive serious damage made by predators or forces of nature. Some species belonging to Linckia, Ophidiaster and Phataria shed single arms that regenerate the disc and the remaining rays to form a complete individual. Some of these also reproduce asexually by parthenogenesis.
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. Two forms are recognised: the nominate and formarobusta from the Strait of Tartary. It mostly preys on large bivalve molluscs, and it is mostly preyed on by other species of starfish. Population booms in Japan can affect the harvest of mariculture operations and are costly to combat.
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.
Linckia is a genus of sea stars found mainly in the Indo-Pacific region. They are known to be creatures with remarkable regenerative abilities, and capable of defensive autotomy against predators. They reproduce asexually.
Linckia guildingi, also called the common comet star, Guilding's sea star or the green Linckia, is a species of sea star reported from the shallow waters of the tropical Pacific Ocean, Indian Ocean, Atlantic Ocean and the Caribbean Sea.
Choriaster is monotypic genus in the family Oreasteridae containing the single species Choriaster granulatus commonly known as the granulated sea star. Other common names include big-plated sea star and doughboy starfish. This species is harmless to humans.
Asexual reproduction in starfish takes place by fission or through autotomy of arms. In fission, the central disc breaks into two pieces and each portion then regenerates the missing parts. In autotomy, an arm is shed with part of the central disc attached, which continues to live independently as a "comet", eventually growing a new set of arms. Although almost all sea stars can regenerate their limbs, only a select few sea star species are able to reproduce in these ways.
Linckia columbiae is a species of starfish in the family Ophidiasteridae. It is found in the East Pacific where it ranges from California (USA) to northwest Peru, including offshore islands such as the Galápagos. Common names include fragile star, Pacific comet sea star and variable sea star.
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.
Evasterias troschelii is a species of starfish in the family Asteriidae. Its common names include the mottled star, false ochre sea star and Troschel's true star. It is found in Kamchatka and the north western coast of North America.
Ophidiaster granifer, the grained seastar, is a species of starfish in the family Ophidiasteridae. It is found in the Red Sea and the Indo-Pacific and is the only known species of starfish to reproduce by parthenogenesis.
Thyca crystallina is a species of sea snail, a marine gastropod mollusc in the family Eulimidae. It is one of nine species within the genus Thyca, all of which are parasitic on starfish in the Indo-Pacific Ocean. This species was first described in 1846 by the American conchologist Augustus Addison Gould as Pileopsis crystallina but was later transferred to Thyca.
Aquilonastra conandae is a species of starfish from the family Asterinidae found near the Mascarene Islands in the Indian Ocean. It is known for its asexual reproduction and is fissiparous. It is a small starfish, discrete and camouflaged, and occurs in coral reefs in the surf zone of large waves. The species was described in 2006 by Australian marine biologists P. Mark O'Loughlin and Francis Winston Edric Rowe, and gets its name from Chantal Conand.
Starfish, or sea stars, are radially symmetrical, star-shaped organisms of the phylum Echinodermata and the class Asteroidea. Aside from their distinguished shape, starfish are most recognized for their remarkable ability to regenerate, or regrow, arms and, in some cases, entire bodies. While most species require some part of the central body to be intact in order to regenerate arms, a few tropical species can grow an entirely new starfish from a portion of a severed limb. Starfish regeneration across species follows a common three-phase model and can take up to a year or longer to complete. Though regeneration is used to recover limbs eaten or removed by predators, starfish are also capable of autotomizing and regenerating limbs to evade predators and reproduce.
Zenopontonia soror, the starfish shrimp or seastar shrimp, is a species of shrimp in the family Palaemonidae. It is found in shallow water in the tropical Indo-Pacific region. It lives in association with a starfish, often changing its colour to match that of its host.
