Partners for Life: A Brittle Star and Its Octocoral Host

Throughout the New England and Corner Rise seamounts of the western North Atlantic Ocean, several ophiuroid species are conspicuously epizoic on octocorals. One species, Ophiocreas oedipus, was found only on the chrysogorgiid octocoral Metallogorgia melanotrichos. Colonies of M. melanotrichos were collected from 11 seamounts during expeditions in 2003, 2004, and 2005 at depths between 1300 and 2200 m. O. oedipus is obligately associated with M. melanotrichos, leading a solitary existence on all octocorals observed. Evidence suggests that a young brittle star settles directly on a young octocoral and the 2 species then grow, mature, and senesce together. The brittle star benefits directly by being above the bottom for suspension feeding and is passively protected by the octocoral, but the latter, as far as we have been able to determine, Seems neither to benefit nor be disadvantaged by the relationship.