ABSTRACT
The brittle-stars Ophionereis reticulate, Ophiocoma pumila and Ophiolepis impressa, in addition to other species, were found under slabs of coral rubble lying on sand, in 1-2 m of water in Jamaica. Analysis of the species distribution under stones showed that O. reticulate, O. pumila and O. impressa were negatively associated with each other, i.e. did not generally occur under the same stone. Ophionereis reticulate and Ophiocoma pumila were shown to alter the crevice dimensions under a stone, by shifting sand, but Ophiolepis impressa did not. Experiments were run to determine if competition for space occurred between O. reticulata and O. impressa. Under experimental conditions competition for space was found to occur between the two species and O. reticulate was the competitively dominant species. The interaction took 2-8 days. Alteration of the crevice dimensions is suggested as the competitive mechanism.
