''Ophiura ophiura'' or the serpent star is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

brittle star Brittle stars, serpent stars, or ophiuroids (; ; referring to the serpent-like arms of the brittle star) are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their flexible arms for locomot ...

in the order Ophiurida. It is typically found on coastal seabeds around northwestern Europe.

Description

''Ophiura ophiura'' has a circular central disc up to 35 mm (1.5 in) wide and five radially arranged, narrow arms each up to long. The general colour is mottled reddish-brown with a paler underside. Both the top and the underside of the disc are covered with calcareous plates. The arms are joined to the top rather than the edge of the disc and further small, articulating plates allow the arms to bend from side to side. Small spines on the arms lie flat against the surface. Four larger plates occur across the root of each arm with the outer pair having a comb-like edge, with 20 to 30 fine papillae in each.''Ophiura ophiura'' (Linnaeus, 1758)
''National Museums of Northern Ireland''. Retrieved August 10, 2011. A pair of pores is seen between the underside plates at the root of the arms.A brittlestar - ''Ophiura ophiura''
'' Marine Life Information Network''. Retrieved August 10, 2011. Five large mouth-shield plates are on the underside of the disc which surround the central mouth. The teeth are in a vertical row above each of the five jaws and about five mouth papillae are on each side of the jaw.Macrobenthos of the North Sea - Echinodermata
''Marine Species Identification Portal''. Retrieved August 10, 2011.

Distribution and habitat

''Ophiura ophiura'' is found on the sea floor in the northeast

Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...

and the

North Sea The North Sea lies between Great Britain, Denmark, Norway, Germany, the Netherlands, Belgium, and France. A sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian Se ...

from

Norway Norway, officially the Kingdom of Norway, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. The remote Arctic island of Jan Mayen and the archipelago of Svalbard also form part of the Kingdom of ...

and

Sweden Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic count ...

south to

Madeira Madeira ( ; ), officially the Autonomous Region of Madeira (), is an autonomous Regions of Portugal, autonomous region of Portugal. It is an archipelago situated in the North Atlantic Ocean, in the region of Macaronesia, just under north of ...

and the

Mediterranean Sea The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...

. It is found below low-tide mark in the neritic zone down about 200 m, on sandy bottoms. It shows a preference for sediments with a fine grain size and about 35% mud content. It is a common species with 20 to 50 individuals occurring per square metre in some years in the North Sea.

Biology

''Ophiura ophiura'' is an active brittle star, moving with a jerky swimming action of its legs and sometimes burrowing. It is a filter feeder, feeding on a wide range of food, but also a bottom-feeding

carnivore A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they ar ...

and detritivore. It can regenerate its arms if they are damaged or torn off. Sexual reproduction takes place during the summer. The larvae are the typical ophiopluteus larvae of brittle stars and later settle on the sea bed and develop into juveniles.

Ecology

The copepod, ''Parartotrogus richardi'', is an ectoparasite of ''O. ophiura''. In the Clyde sea fishery for scampi ('' Nephrops norvegicus'') in

Scotland Scotland is a Countries of the United Kingdom, country that is part of the United Kingdom. It contains nearly one-third of the United Kingdom's land area, consisting of the northern part of the island of Great Britain and more than 790 adjac ...

, the unwanted invertebrates that get caught up in the trawl include ''O. ophiura'', as well as the starfish '' Asterias rubens''. A study undertaken to discover the survival rate of these animals when discarded and returned to the water found that uninjured ''A. rubens'' had a mortality rate of 4%, whereas virtually all the ''O. ophiura'' died within 14 days, even when they were returned to the sea immediately after being caught. Another study examined the rate at which the discarded invertebrates sank to the bottom and their ultimate fates. ''O. ophiura'' sank relatively slowly and was preyed upon by seabirds, and the arms were eaten by fish. On the sea bed, a succession of benthic scavengers thrived on their remains with crangonid shrimps and

crab Crabs are decapod crustaceans of the infraorder Brachyura (meaning "short tailed" in Greek language, Greek), which typically have a very short projecting tail-like abdomen#Arthropoda, abdomen, usually hidden entirely under the Thorax (arthropo ...

s such as '' Carcinus maenas'' and '' Liocarcinus depurator'' being prominent. In six hours, little remained except the limbs of crustaceans and the discs of ophiuroids. The crab '' Pagurus bernhardus'' was the most likely scavenger to consume ''O. ophiura'' in baited traps.

Evolution

Extremely well-preserved fossils of ''Ophiura ophiura'' (=''Ophiura texturata'') have been recorded from a

Late Pliocene Late or LATE may refer to: Everyday usage * Tardy, or late, not being on time * Late (or the late) may refer to a person who is dead Music * Late (The 77s album), ''Late'' (The 77s album), 2000 * Late (Alvin Batiste album), 1993 * Late!, a pseudo ...

and early Pleistocene-aged fossil assemblage near Parma, Italy. They inhabited an offshore ecosystem off the paleo-

Adriatic Sea The Adriatic Sea () is a body of water separating the Italian Peninsula from the Balkans, Balkan Peninsula. The Adriatic is the northernmost arm of the Mediterranean Sea, extending from the Strait of Otranto (where it connects to the Ionian Se ...

between hypoxia events; during hypoxia events, they are replaced in the assemblage by the more tolerant '' Ophiura albida''.

References

{{Taxonbar, from=Q2223690 Ophiuridae Echinoderms described in 1758 Taxa named by Carl Linnaeus