An echinoderm is any deuterostomal animal of the phylum Echinodermata, which includes starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, as well as the sessile sea lilies or "stone lilies". While bilaterally symmetrical as larvae, as adults echinoderms are recognisable by their usually five-pointed radial symmetry, and are found on the sea bed at every ocean depth from the intertidal zone to the abyssal zone. The phylum contains about 7,600 living species, making it the second-largest group of deuterostomes after the chordates, as well as the largest marine-only phylum. The first definitive echinoderms appeared near the start of the Cambrian.
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.
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.
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. Fragmentation occurs on star fishes.
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.
Solaster dawsoni, the morning sun star, is a species of starfish in the family Solasteridae. It is found on either side of the northern Pacific Ocean. It has two subspecies:
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 distinguishing shape, starfish are most recognized for their remarkable ability to regenerate, or regrow, arms and, in some cases, entire bodies. While most species require the central body to be intact in order to regenerate arms, a few tropical species can grow an entirely new starfish from just 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.
Ophiothela mirabilis is a species of ophiuroid brittle star within the family Ophiotrichidae. O. mirabilis is an epizoic species which have a non-parasitic relationship with host sponges or gorgonians. Although native to the Pacific Ocean, it has invaded the Caribbean and southwestern Atlantic since late 2000. Many of its characteristics, including reproduction and diet, allow O. mirabilis opportunities to quickly propagate and spread through habitats.
