Brittlestar

• It is one of the animals that contribute most to turning over and oxygenating the muddy bottoms of the north-eastern Atlantic, and its densities can exceed a thousand individuals per square metre.
• It is bioluminescent: the arms emit greenish flashes when something touches them, probably to give the predator away to a larger one.
• Fish and crustaceans constantly nip off the tips of the arms that protrude, and the brittle star regrows them endlessly; that cycle of loss and regeneration is in itself a pathway of energy transfer to the rest of the community.
• It lives buried with its disc several centimetres down and extends its arms into the water to capture particles, a way of life straddling the sediment and the water column.
• It is bioluminescent: the arms flash blue when something touches them, probably to startle a predator or to signal that the arm is expendable.
• Flatfish eat the arms that protrude, and it regenerates them continuously. That constant production of new tissue makes it one of the most important species in carbon recycling on muddy bottoms.
• Its burrows bioturbate the sediment and oxygenate deeper layers, which alters the chemistry of the seabed.
• It is used as a model for studying the effects of ocean acidification on regeneration and calcification.

Habitat & environment

Muddy bottoms of the continental shelf, from 5 to 200 m

Sources consulted: O.F. Müller (1776); Wood et al. (2008), Proceedings of the Royal Society B; Marine Life Information Network