Ophiocomina nigra, commonly known as the black brittle star or black serpent star, is a species of marine invertebrate in the order Ophiurida. It occurs in the north-eastern Atlantic Ocean, the North Sea and the Mediterranean Sea.[1]
O. nigra is a large brittle star with five narrow arms up to 125mm long and a quite distinct central disc which is up to 25mm wide. The general colour is black or varying shades of brown, but pale coloured specimens occasionally occur. The upper surface of the disc is covered with fine granules which obscure the plates which cover the surface. On the underside the granules are restricted to the outer portion and the plates are visible towards the central mouth. This is surrounded by the feeding apparatus known as Aristotle's lantern with five toothed jaws each with oval jaw plates.[2] There is a comb-like arrangement of spines down either side of the arms giving them a bristly appearance.[3] On the upper side, each arm segment is covered by a broad plate with 5 to 7 spines. On the underside there are tube feet but these have no suckers.[2]
O. nigra occurs in the eastern Atlantic Ocean from Norway south to the Azores, and also the North Sea and the Mediterranean Sea.[2] It is found on rocks, boulders and gravel in the neritic zone down to about one hundred metres but is occasionally found at greater depths.[3] It is tolerant of low salinity levels.[2]
O. nigra is a predator, scavenger and filter feeder. It catches pieces of organic detritus and small invertebrate prey with its arms and thrusts them into its mouth. It can scavenge from carcases or graze on algal films.[4] As a suspension feeder, it raises one or more arms into the current of water flowing past. There is a net of mucous threads among the spines on the arms which trap plankton and other organic floating matter. These are then rolled into boluses and transported to the mouth by ciliary currents and the tube feet.[5]
Breeding of O. nigra takes place in June in the Firth of Clyde, Scotland. A large female is often found in association with a smaller male, which clings above or below her. Fertilisation however takes place in the water column and is a chance meeting of two gametes.[6] The larvae are planktonic and settle out after several months. The species seems to be slow-growing and long-lived, not becoming mature before the age of three or four years.[4]
O. nigra is often found living in association with another brittle star, Ophiothrix fragilis.[7] Numerous individuals of these two species sometimes form dense communities with hundreds of brittle stars per square metre. These beds may extend several hundred square metres over sandy and pebbly sediment on the sea floor and contain millions of brittle stars.[8] These can be either O. nigra or O. fragilis, or a mixed community of the two. The vast social agglomerations can be advantageous in enabling the brittle stars to filter feed in fast moving currents which would otherwise sweep them away.[8] Often the bed consists of adults and newly settled juveniles, with intermediate sized individuals living elsewhere. Other echinoderms likely to be in the same vicinity (and enjoying the feast) are the predatory starfish, Asterias rubens, Luidia ciliaris and Crossaster papposus and the sea urchins, Echinus esculentus and Psammechinus miliaris. Also present are likely to be the crabs Cancer pagurus, Necora puber and Liocarcinus spp., and the hermit crab, Pagurus bernhardus. On rocky outcrops among the seething mass of brittle stars the soft coral, Alcyonium digitatum, the hydroid, Nemertesia antennina and the sea anemone, Metridium senile, are often found. Another sea anemone, Urticina felina, may be semi-buried in the sediment and surrounded by an area clear of brittle stars.[8][9]
Ophiocomina nigra, commonly known as the black brittle star or black serpent star, is a species of marine invertebrate in the order Ophiurida. It occurs in the north-eastern Atlantic Ocean, the North Sea and the Mediterranean Sea.
Ophiure noire
Ophiocomina nigra, communément appelé Ophiure noire, est une espèce d'ophiures de la famille des Ophiuridae.
Comme la plupart des ophiures, l'ophiure noire est formée d'un disque central mou et aplati autour duquel rayonnent 5 bras allongés et effilés, permettant une reptation rapide[1].
Le disque central rigide mesure 3 cm de diamètre maximum, il est pentagonal et finement granuleux ; il est d'ordinaire d'un noir profond mais peut être décoré de motifs bruns. Les cinq bras sont relativement longs (jusqu'à 15 cm), et s'affinent vers la pointe ; ils sont généralement noirs mais parfois eux aussi décorés de brun. Le long des bras, de chaque côté, se trouve une rangée d'écailles qui ont pris la forme de piquants (10 à 14 par segment), et disposés en peigne[2].
On trouve cette ophiure en Atlantique du Nord-Est et Méditerranée[2].
Son habitat de prédilection est dans les fonds détritiques, rocheux, ou sableux-vaseux, à une profondeur variant de la surface à près de 400 m de profondeur[2]. Ophiocomina nigra se trouve le long de la bande littorale, affectionnant les eaux riches en nutriments, turbides ou polluées. On la trouve donc logiquement dans les ports et les embouchures d'égouts, parfois en densités importantes[2].
L'ophiure est omnivore opportuniste à tendance charognarde, pouvant manger des particules en suspension, des débris organiques, des feutrages bactériens, mais aussi des charognes ou même exercer une chasse à de petits animaux vivants[2].
La reproduction est gonochorique, et mâles et femelles relâchent leurs gamètes en même temps grâce à un signal phéromonal, en pleine eau, où œufs puis larves (appelées ophiopluteus) vont évoluer parmi le plancton pendant quelques semaines avant de rejoindre le sol.
Ophiure noire
Ophiocomina nigra, communément appelé Ophiure noire, est une espèce d'ophiures de la famille des Ophiuridae.
Ophiocomina nigra is een slangster uit de familie Ophiocomidae.
De wetenschappelijke naam van de soort werd in 1789 gepubliceerd door Peter Christian Abildgaard in deel 3 van Zoologia danica, een werk van Otto Frederik Müller dat na diens dood door Abildgaard werd voltooid.
De soort vangt zijn voedsel door een slijm uit te scheiden dat zich vormt tot draden. Deze draden dienen als hengels, waarmee plankton en andere organismen worden gevangen.[1]
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