Ophiura ophiura
A brittle star found on sandy seabeds around northwestern Europe.
Ophiura ophiura, called the serpent star, is a brittle star belonging to the order Ophiurida. It lives on coastal seafloors near northwestern Europe.
Its body has a round central disc up to 35 mm wide, with five narrow arms arranged around it, each reaching up to 140 mm long. The animal is mottled reddish-brown on top and paler underneath. Both the upper and lower surfaces of the disc are covered with calcareous plates. The arms attach to the top of the disc, not the edge, and small articulating plates let them bend sideways. Tiny spines on the arms lie flat. At the base of each arm are four larger plates; the outer pair have comb-like edges with 20 to 30 fine papillae each. A pair of pores sits between the underside plates at the arm roots. On the disc’s underside, five large mouth-shield plates surround the central mouth. Each of the five jaws has a vertical row of teeth above it, and about five mouth papillae line each side of the jaw.
This brittle star is found on the seafloor in the northeast Atlantic Ocean and the North Sea, from Norway and Sweden south to Madeira and the Mediterranean Sea. It occurs below the low-tide mark in the neritic zone down to about 200 m, on sandy bottoms. It prefers fine-grained sediment with about 35% mud content. It is common, with 20 to 50 individuals per square meter in some years in the North Sea.
Ophiura ophiura is active, moving with a jerky swimming motion of its legs and sometimes burrowing. It filter-feeds on a wide range of food, but also acts as a bottom-feeding carnivore and detritivore. It can regrow arms that are damaged or torn off. Sexual reproduction happens in summer. The larvae are typical ophiopluteus larvae, which later settle on the seabed and develop into juveniles.
The copepod *Parartotrogus richardi* is an ectoparasite of *O. ophiura*. In the Clyde sea fishery for scampi (*Nephrops norvegicus*) in Scotland, unwanted invertebrates caught in trawls include *O. ophiura* and the starfish *Asterias rubens*. A study on survival rates after discarding found that uninjured *A. rubens* had a 4% mortality rate, while nearly all *O. ophiura* died within 14 days, even if returned to the water immediately. Another study looked at how fast discarded invertebrates sank and what happened to them. *O. ophiura* sank slowly, was eaten by seabirds, and its arms were consumed by fish.
Quick Facts
- Genus
- Ophiura
Facts from the source article.
Lore & Background
Ophiura ophiura has a circular central disc up to 35 mm wide and five narrow arms each up to 140 mm long. The general colour is mottled reddish-brown with a paler underside. Both the top and underside of the disc are covered with calcareous plates. The arms are joined to the top rather than the edge of the disc, and 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 bearing 20 to 30 fine papillae. A pair of pores is seen between the underside plates at the root of the arms. Five large mouth-shield plates surround the central mouth on the underside of the disc. 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.
It is found on the sea floor in the northeast Atlantic Ocean and the North Sea from Norway and Sweden south to Madeira and the Mediterranean Sea, below the low-tide mark in the neritic zone down about 200 m, on sandy bottoms with a preference for fine sediment and about 35% mud content. It is a common species, with 20 to 50 individuals per square metre in some years in the North Sea.
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 and detritivore. It can regenerate its arms if damaged or torn off. Sexual reproduction takes place during the summer, and the larvae are the typical ophiopluteus larvae of brittle stars, later settling on the sea bed and developing into juveniles.
Reader's Guide
Ophiura ophiura is significant in the context of trawl fisheries discards. In the Clyde sea fishery for scampi (Nephrops norvegicus) in Scotland, it is among the unwanted invertebrates caught in trawls. A study found that virtually all O. ophiura died within 14 days when discarded and returned to the sea, even immediately after capture, whereas uninjured starfish Asterias rubens had a mortality rate of only 4%. Another study examined the fate of discarded invertebrates: O. ophiura sank relatively slowly and was preyed upon by seabirds, and its arms were eaten by fish. On the sea bed, a succession of benthic scavengers thrived on their remains, with crangonid shrimps and crabs such as Carcinus maenas and Liocarcinus depurator being prominent. Within 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.
The copepod Parartotrogus richardi is an ectoparasite of O. ophiura. Extremely well-preserved fossils of Ophiura ophiura (also recorded as Ophiura texturata) have been found in a Late Pliocene and early Pleistocene-aged fossil assemblage near Parma, Italy. These fossils inhabited an offshore ecosystem off the paleo-Adriatic Sea between hypoxia events; during hypoxia events, they are replaced in the assemblage by the more tolerant Ophiura albida.
Did You Know?
- Ophiura ophiura can regenerate its arms if they are damaged or torn off.
- Virtually all discarded O. ophiura died within 14 days after being caught in trawls and returned to the sea.
More in Sea Cucumbers and Brittle Stars, Part 3 1-24
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