Ophiocomina nigra
A large brittle star forming dense beds in the north-eastern Atlantic.
The black brittle star, or black serpent star, *Ophiocomina nigra*, is a marine invertebrate from the order Ophiurida. It lives in the northeastern Atlantic Ocean, the North Sea, and the Mediterranean Sea. This species is a large brittle star, with five slender arms reaching up to 125 mm in length and a distinct central disc up to 25 mm wide. Its color is typically black or various shades of brown, though pale individuals are occasionally seen. The upper disc is covered in fine granules that hide the underlying plates, while on the underside, granules are only on the outer part, leaving the plates visible near the central mouth. The mouth is surrounded by Aristotle's lantern, a feeding structure with five toothed jaws, each bearing oval jaw plates. A comb-like row of spines runs down each side of the arms, giving them a bristly look. On the upper arm, each segment has a broad plate with five to seven spines; on the underside are tube feet, but these lack suckers.
This brittle star ranges from Norway south to the Azores, across the North Sea, the Mediterranean Sea, and into the Indian Ocean. It lives on rocks, boulders, and gravel in the neritic zone down to about 100 meters, though it is occasionally found deeper. It tolerates low salinity.
*O. nigra* is a predator, scavenger, and filter feeder. It uses its arms to capture pieces of organic detritus and small invertebrate prey, pushing them into its mouth. It can scavenge carcasses or graze on algal films. As a suspension feeder, it raises one or more arms into the current. A net of mucous threads among the arm spines traps plankton and other floating organic matter, which is rolled into balls and moved to the mouth by ciliary currents and tube feet.
Breeding occurs in June in the Firth of Clyde, Scotland. A large female is often found with a smaller male clinging above or below her. Fertilization happens in the water column through chance meeting of gametes. The larvae are planktonic and settle after several months. The species grows slowly and lives long, not reaching maturity until three or four years old.
*O. nigra* often lives with another brittle star, *Ophiothrix fragilis*. Many individuals of both species sometimes form dense communities, with hundreds per square meter.
Quick Facts
- Taxon
- Ophiocomina nigra
Facts from the source article.
Lore & Background
Ophiocomina nigra is a large brittle star with five narrow arms up to 125 mm long and a distinct central disc up to 25 mm wide. Its general colour is black or varying shades of brown, though pale specimens occasionally occur. The upper surface of the disc is covered with fine granules that obscure the plates, while on the underside granules are restricted to the outer portion and plates are visible toward the central mouth. The mouth is surrounded by Aristotle's lantern with five toothed jaws, each with oval jaw plates. A comb-like arrangement of spines down either side of the arms gives them a bristly appearance; each upper arm segment bears a broad plate with 5 to 7 spines, and the underside has tube feet without suckers.
It occurs in the eastern Atlantic Ocean from Norway south to the Azores, the North Sea, the Mediterranean Sea, and the Indian Ocean. It is found on rocks, boulders, and gravel in the neritic zone down to about one hundred metres, occasionally at greater depths, and is tolerant of low salinity. O. nigra is a predator, scavenger, and filter feeder. It catches organic detritus and small invertebrate prey with its arms, scavenges from carcasses, grazes on algal films, and suspension-feeds by raising arms into currents. A net of mucous threads among the arm spines traps plankton, which is rolled into boluses and transported to the mouth by ciliary currents and tube feet.
Breeding takes place in June in the Firth of Clyde, Scotland. A large female is often found with a smaller male clinging above or below her, but fertilisation occurs in the water column. The larvae are planktonic and settle after several months. The species is slow-growing and long-lived, not becoming mature before three or four years of age.
Reader's Guide
Ophiocomina nigra is significant for its ecological role as a predator, scavenger, and filter feeder, and for its ability to form dense communities with Ophiothrix fragilis. These beds, which may extend several hundred square metres over sandy and pebbly sediment, contain hundreds of brittle stars per square metre and can be composed of either species or a mix. The vast social agglomerations are advantageous for filter feeding in fast-moving currents that would otherwise sweep individuals away. The beds often consist of adults and newly settled juveniles, with intermediate-sized individuals living elsewhere. Associated echinoderms in the same vicinity include predatory starfish such as Asterias rubens, Luidia ciliaris, and Crossaster papposus, and sea urchins Echinus esculentus and Psammechinus miliaris. Also present are crabs Cancer pagurus, Necora puber, and Liocarcinus spp., and the hermit crab Pagurus bernhardus. On rocky outcrops among the 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. The species' tolerance of low salinity and its slow growth and late maturity further shape its distribution and population dynamics.
Did You Know?
- Ophiocomina nigra has five narrow arms up to 125 mm long and a central disc up to 25 mm wide.
- It is tolerant of low salinity levels.
- It often forms dense communities with another brittle star, Ophiothrix fragilis.
Frequently Asked Questions
What is Ophiocomina nigra?
Ophiocomina nigra, commonly known as the black brittle star or black serpent star, is a marine invertebrate classified under the order Ophiurida. It is regarded as one of the larger species among brittle stars and is often found forming dense aggregations in its native waters.
How big does Ophiocomina nigra get?
Its five slender arms can extend to a maximum of 125 mm, while the central disc measures up to 25 mm in width. The upper surface of the disc is covered in fine granules that obscure the underlying plates, and the animal is typically black or various shades of brown, though pale specimens do occasionally appear.
Where does Ophiocomina nigra live?
This species ranges across the northeastern Atlantic Ocean, the North Sea, and the Mediterranean Sea. It occupies the neritic zone, generally at depths down to roughly one hundred metres, though it has been recorded at greater depths on occasion.
When does Ophiocomina nigra reproduce and how long until it matures?
In the Firth of Clyde, breeding activity peaks in June. The animal reaches sexual maturity at approximately three to four years of age.
Can Ophiocomina nigra tolerate low-salinity conditions?
Yes, this brittle star is notably tolerant of reduced salinity levels, which helps it persist in more sheltered or partially enclosed coastal habitats. That resilience, combined with its tendency to form dense beds, makes it a conspicuous component of northeastern Atlantic benthic communities.
More in Sea Cucumbers and Brittle Stars, Part 2 1-24
Spotted an error? Know more?
Reader corrections go straight into our review queue. Suggest an edit · How this site is sourced