Occurrence of Pedunculate Barnacle, Octolasmis spp. in Blue Swimming Crab, Portunus pelagicus

Barnacles are symbiont and harm to the crabs when they are in large numbers. They will affect the respiration, normal activity and growth of the crabs. The prevalence, mean intensity and identification of pedunculate barnacle, Octolasmis spp. on blue swimming crab, Portunus pelagicus from coastal area of Kuala Terengganu were studied. The site specificity of the different species of Octolasmis attached was examined. The crabs were measured and weight. The crabs were euthanized by put in ice until no movement. The Octolasmis were observed from the surfaces and gills or brachial chamber. The Octolasmis were observed from each gill. The prevalence and mean intensity were calculated. The Octolasmis were preserved in 70% alcohol and mounting using glycerine jelly to make permanent slide. A total of all 13 crabs were infested by four species of Octolasmis which is 218 Oc- tolasmis angulata, 191 Octolasmis warwickii, 16 Octolasmis tridens and 218 Octolasmis lowei. Octolasmis angulate showed highest prevalence (84.62%) and lowest prevalence was O. lowei (23.08%) and O. warwickii (23.08%). The barnacles were attached to the gill, carapace, abdomen and also walking legs. Barnacle occurred most frequently on the gill part by having 371 (57.70%) barnacles compared to other areas, 272 (42.30%) barnacles. The distributions of barnacle in this study suggest distal areas are more susceptible in infestation by Octolasmis spp. However, they did not show site specificity on the gill areas because it depends on the water current.