Some observations on the epizoic barnacle Octolasmis angulata within the branchial chambers of an Australian swimming crab

An epizoic stalked barnacle, Octolasmis angulata, was identified within the branchial chambers of Charybdis callianassa, a swimming crab from Moreton Bay, Queensland, Australia, making this crab a new host for O. angulata. In the present study fifty-two crabs, 30-49 mm carapace width, were dissected , and thirty-three were found to have the epizoite. The number and position of the O. angulata within the branchial chambers were noted. Octolasmis an gulata is principally found attached to the cuticle of the anterior chamber wall in the epibranchial space, although attachment to the gills does occu r. Charybdis callianassa is also parasitized by the sacculinid barnacle Het erosaccus lunatus, and one such parasitized crab contained eighty-seven O. angulata, the highest number recorded in the present study. The factors gov erning O. angulata distribution within the branchial chambers of C. callian assa are discussed.