Notched Brittle Star

Adult O. sarsii have arms that can extend up to 90 millimeters or 3-4 times the disk size. Their central disks are commonly up to 25 millimeters in diameter but can be as large as 40 millimeters in diameter. Their disk is rigid and heavily calcified. This is much larger than the species Ophiocten sericeum, a different species of cold water brittle star that inhabits the same habitats. O. sericeum only has a maximum disk size of 18 mm. As it transitions out of its larval stage, the central disk becomes a pentagonal shape with small perforations. As it continues to grow, it gains spines, arms and arm joints, as well as protective plates.

They have been found in the northern parts of the Atlantic and Pacific Oceans, as well as the entirety of the Arctic Ocean. Their distribution is primarily in the bathyal zone of the open ocean, in some parts covering as much as 96% of the seabed. In the Arctic sea, they mostly inhabit slopes and shelves with soft bottoms. They have been found to outnumber all other brittle star species in their habitat, making up 71% of the abundance in the benthic and epibenthic parts of the Arctic Ocean.

They are primarily carnivorous, feeding on mostly amphipods. But they have also been found to eat arthropods, molluscs, cnidarians and annelids making them trophic, generalist feeders. However, their diet is mostly restricted to the amphipod families Ampeliscidae and Lysianassidae, which made up 54-70% of their stomach contents in during sampling periods in an experiment done by Harris et al., 2009.

When fresh O. sarsii tissue is collected, sulfated steroidal polyols can be isolated from it. These steroids can potentially be used for anti-HIV medication since they can inhibit some enzymes and cause cell death. THA found in the limbs of them can be isolated into an anti-inflammatory and anti-allergenic substance. Since it is so abundant, they are widely used as a source of THA. There are no known fisheries for O. sarsii and other Arctic brittle stars.