Ophiura ophiura
Encyclopedia
Ophiura ophiura or the serpent star is a species
of brittle star
in the order
Ophiurida
. It is typically found on coastal seabed
s around northwestern Europe.
e in each. There are a pair of pores between the underside plates at the root of the arms. There are five large mouth-shield plates 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 there are about five mouth papilla
e on each side of the jaw.
and the North Sea
from Norway
and Sweden
south to Madeira
and the Mediterranean Sea
. It is found below low tide mark in the neritic zone
down to a depth of about two hundred metres, on sandy bottoms. It shows a preference for sediments with a fine grain size and approximately 35% mud content. It is a common species with twenty individuals occurring per square metre in some years in the North Sea with a maximum of fifty.
It is a filter feeder
, feeding on a wide range of food, but also a bottom-feeding carnivore
and detrivore. 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.
, Parartotrogus richardi, is an ectoparasite of O. ophiura.
In the Clyde Sea fishery for scampi (Nephrops norvegicus) in Scotland
, the unwanted invertebrate
s that get caught up in the trawl include O. ophiura as well as the starfish Asterias rubens. A study was undertaken to discover the survival rate of these animals when discarded and returned to the water. It was 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 were preyed upon by seabirds, and the arms were eaten by fish. On the sea bed it was found that a succession of benthic scavengers thrived on their remains with crangonid shrimps
and crab
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.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of brittle star
Brittle star
Brittle stars or ophiuroids are echinoderms in the class Ophiuroidea closely related to starfish. They crawl across the seafloor using their flexible arms for locomotion. The ophiuroids generally have five long slender, whip-like arms which may reach up to in length on the largest specimens...
in the order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
Ophiurida
Ophiurida
The Ophiurida are an order of echinoderms within the class Ophiuroidea. It includes the vast majority of living brittle stars.-Characteristics:The upper surface of the disk of Ophiurida is covered with scales....
. It is typically found on coastal seabed
Seabed
The seabed is the bottom of the ocean.- Ocean structure :Most of the oceans have a common structure, created by common physical phenomena, mainly from tectonic movement, and sediment from various sources...
s around northwestern Europe.
Description
O. ophiura has a circular central disc up to 35 mm (1.5 in) wide and five radially arranged, narrow arms each up to 140 mm (6 in) 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. There are small spines on the arms which lie flat against the surface. There are four larger plates across the root of each arm with the outer pair having a comb-like edge, with twenty to thirty fine papillaPapilla
The term papilla generally means a nipple-like structure, and may refer to:* Mammary papilla, or nipple* Amphibian papilla and basal papilla, part of the inner ear of the frog.* Interdental papilla, part of the gingiva between teeth...
e in each. There are a pair of pores between the underside plates at the root of the arms. There are five large mouth-shield plates 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 there are about five mouth papilla
Papilla
The term papilla generally means a nipple-like structure, and may refer to:* Mammary papilla, or nipple* Amphibian papilla and basal papilla, part of the inner ear of the frog.* Interdental papilla, part of the gingiva between teeth...
e on each side of the jaw.
Distribution and habitat
O. ophiura is found on the sea floor in the north east Atlantic OceanAtlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
and the North Sea
North Sea
In the southwest, beyond the Straits of Dover, the North Sea becomes the English Channel connecting to the Atlantic Ocean. In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively...
from Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
and Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
south to Madeira
Madeira
Madeira is a Portuguese archipelago that lies between and , just under 400 km north of Tenerife, Canary Islands, in the north Atlantic Ocean and an outermost region of the European Union...
and the Mediterranean Sea
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
. It is found below low tide mark in the neritic zone
Neritic zone
The neritic zone, also called coastal waters, the coastal ocean or the sublittoral zone, is the part of the ocean extending from the low tide mark to the edge of the continental shelf, with a relatively shallow depth extending to about 200 meters...
down to a depth of about two hundred metres, on sandy bottoms. It shows a preference for sediments with a fine grain size and approximately 35% mud content. It is a common species with twenty individuals occurring per square metre in some years in the North Sea with a maximum of fifty.
Biology
O. ophiura is an active brittle star, moving with a jerky swimming action of its legs and sometimes burrowing.It is a filter feeder
Filter feeder
Filter feeders are animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feeding are clams, krill, sponges, baleen whales, and many fish and some sharks. Some birds,...
, feeding on a wide range of food, but also a bottom-feeding carnivore
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...
and detrivore. 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 copepodCopepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
, Parartotrogus richardi, is an ectoparasite of O. ophiura.
In the Clyde Sea fishery for scampi (Nephrops norvegicus) in Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
, the unwanted invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s that get caught up in the trawl include O. ophiura as well as the starfish Asterias rubens. A study was undertaken to discover the survival rate of these animals when discarded and returned to the water. It was 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 were preyed upon by seabirds, and the arms were eaten by fish. On the sea bed it was found that a succession of benthic scavengers thrived on their remains with crangonid shrimps
Crangonidae
The family Crangonidae is a taxon of shrimps, of the superfamily Crangonoidea, including the commercially important species Crangon crangon. Its type genus is Crangon...
and crab
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...
s such as Carcinus maenas
Carcinus maenas
Carcinus maenas is a common littoral crab, and an important invasive species, listed among the 100 "world's worst alien invasive species". It is native to the north-east Atlantic Ocean and Baltic Sea, but has colonised similar habitats in Australia, South Africa, South America and both Atlantic and...
and Liocarcinus depurator
Liocarcinus depurator
Liocarcinus depurator, sometimes called the harbour crab or sandy swimming crab, is a species of crab found in the North Sea, Atlantic Ocean, Mediterranean Sea and Black Sea. It grows up to in width and long, and it can be distinguished from other crabs, such as the shore crab Carcinus maenas by...
being prominent. In six hours little remained except the limbs of crustaceans and the discs of ophiuroids. The crab Pagurus bernhardus
Pagurus bernhardus
Pagurus bernhardus is the common marine hermit crab of Europe's Atlantic coasts. It is sometimes referred to as the common hermit crab or soldier crab. It is about long, and is found in both rocky and sandy areas, from the Arctic waters of Iceland, Svalbard and Russia as far south as southern...
was the most likely scavenger to consume O. ophiura in baited traps.