An echinoderm is any member of the phylum Echinodermata. The adults are recognisable by their radial symmetry, and include starfish, brittle stars, 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 7,000 living species, making it the second-largest grouping of deuterostomes, after the chordates. Echinoderms are the largest entirely marine 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 occur 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.
Sea pens are colonial marine cnidarians belonging to the order Pennatulacea. There are 14 families within the order; 35 extant genera, and it is estimated that of 450 described species, around 200 are valid. Sea pens have a cosmopolitan distribution, being found in tropical and temperate waters worldwide, as well as from the intertidal to depths of more than 6100 m. Sea pens are grouped with the octocorals, together with sea whips (gorgonians).
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.
The common ling, also known as the white ling or simply the ling, is a large member of the family Lotidae, a group of cod-like fishes. It resembles the related rocklings, but it is much larger and has a single barbel. This species is unrelated to the pink ling, Genypterus blacodes, from the Southern Hemisphere. The common ling is found in the northern Atlantic, mainly off Europe, and into the Mediterranean Basin. It is an important quarry species for fisheries, especially in the northeastern Atlantic, although some doubts exist as the sustainability of the fisheries. As an edible species, it is eaten fresh, frozen, or dried, but also preserved in lye, while the roe is a delicacy in Spain.
The white ghost catshark is a shark of the catshark family Scyliorhinidae found in deep water in the northeast Atlantic between latitudes 57°N and 58°N. A deep-water catshark known from the eastern North Atlantic from depths of 1,014 to 1,800 m, it is known from only a limited number of specimens. It reaches a maximum of 54 cm or 1.7 ft total length which is a medium size for the Apristurus genus.
The common starfish, common sea star or sugar starfish is the most common and familiar starfish in the north-east Atlantic. Belonging to the family Asteriidae, it has five arms and usually grows to between 10–30 cm across, although larger specimens are known. The common starfish is usually orange or brownish in color, and sometimes violet; specimens found in deeper waters are pale. The common starfish is found on rocky and gravelly substrates where it feeds on mollusks and other benthic invertebrates.
Luidia sarsii is a species of starfish. Sand colored with a velvety texture, the species expresses pentamerism or pentaradial symmetry as adults. The five gently tapering arms have conspicuous bands of long white marginal spines in groups of three. Luidia sarsi grow to approximately 20 cm across and are found in deeper water (20 m+) from Norway to the Mediterranean but in deep colder water in the south. They are usually found on muddy sediment and are most active at night, burying themselves under the sand during the day. Luidia sarsii larva develop from a fertilized egg and are unique in a number of respects. The larva of the species attains an unusual size and a juvenile starfish develops inside the larva. During metamorphosis the juvenile migrates to the outside and detaches from the swimming larval bipinnaria stage. The larva continues to live separately for several months.
Sea Life Bangkok Ocean World is an aquarium in Bangkok, Thailand, the largest in South East Asia. It covers approximately 10,000 square meters (110,000 sq ft) with hundreds of different species on display in exhibits totalling about 5,000,000 liters (1,300,000 U.S. gal).
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".
Diplasterias brucei is a species of starfish in the family Asteriidae. It is found in the Pacific Ocean and Southern Ocean. It is a predator and scavenger and is unusual among starfish in that it broods its young.
Eupentacta quinquesemita is a species of sea cucumber, a marine invertebrate with an elongated body, a leathery skin and tentacles surrounding the mouth. It is commonly known as the stiff-footed sea cucumber or white sea cucumber, and occurs on rocky coasts in the northeastern Pacific Ocean.
Novodinia antillensis, the velcro sea star, is a species of starfish in the family Brisingidae. It is found in the deep sea in the tropical and subtropical western Atlantic Ocean, being quite common at a depth of around 500 m (1,640 ft) on the Mesoamerican Reef off Roatán, Honduras.
Paulasterias mcclaini is a species of starfish in the family Paulasteriidae. It is found in deep water at hydrothermal vents.
Paulasterias tyleri is a species of starfish in the family Paulasteriidae. It is found in deep water at hydrothermal vents in the Antarctic. It is the type species of the newly erected genus Paulasterias, the only other member of the genus being Paulasterias mcclaini.
Asterodiscides truncatus, the firebrick starfish, is a species of five-armed starfish in the family Asterodiscididae. It is native to eastern and southern Australia, the Norfolk Ridge and the Kermadec Islands of New Zealand.
Stichaster striatus, the common light striated star, is a species of starfish in the family Stichasteridae, found in the southeastern Pacific Ocean. It was first described by the German zoologists Johannes Peter Müller and Franz Hermann Troschel in 1840.
Meyenaster is a genus of starfish in the family Asteriidae. It is a monotypic genus and the only species is Meyenaster gelatinosus which was first described by the Prussian botanist and zoologist Franz Julius Ferdinand Meyen in 1834. It is found in the southeastern Pacific Ocean on the coasts of South America.
Freyella elegans is a species of deep-water starfish in the family Freyellidae in the order Brisingida, living at abyssal depths in the northwestern Atlantic Ocean.
Thromidia catalai, sometimes called the heavy starfish, is a species of starfish in the family Mithrodiidae in the order Valvatida. It is native to the Indo-Pacific region. Thromidia catalai is one of the largest and heaviest starfishes in the world. It is reported to weigh as much as 6 kg (13 lb) and have a diameter of 60 to 65 cm. This species was first described by the Australian biologists E. C. Pope and F. W. E. Rowe in 1977, the type locality being New Caledonia.
