Marine Animal Encyclopedia
Common Brittlestar Ophiothrix fragilis
This large brittlestar species gathers in dense groups that may cover several square miles of sea bed in areas where there are strong tidal currents. Common brittlestars have been recorded in densities of 2,000 individuals per square yard. Each brittlestar holds up one or two arms into the current to feed on plankton, while linking its remaining arms with surrounding individuals to form a strong mat and prevent itself being swept away. Common brittlestars vary greatly in color, ranging from red, yellow, and orange to brown and gray, and they often have alternate light and dark bands on the arms. The fragile arms of this species are covered in long, untidy spines, while its small disk, which is only 1 in (2 cm) across, has a covering of shorter spines. In the intertidal zone, common brittlestars are not usually found in groups, but occur as individuals hiding in crevices and beneath stones.