SIZE AND LOCATION RELATIONSHIPS OF STALKED BARNACLES OF THE GENUS OCTOLASMIS ON THE MANGROVE CRAB SCYLLA SERRATA

Abstract

Abstract Cyprid larvae of the lepadomorph Octolasmis colonize the gill chambers of the edible mangrove crab Scylla seratta (Forskal, 1755). In a natural population of 856 mangrove crabs from southern Thailand, 260 individuals were infested by 3,670 Octolasmis cor and 1,758 O. angulata, including 1,014 subadults, 168 cyprids, and 38 peduncles of the two species. This population of gill chamber symbionts was examined to investigate the relationship between barnacle size and barnacle spatial distributions. The habitat of the branchial chamber was partitioned for study into gills one through eight, the inside (hypobranchial) and outside (hyperbranchial) gill surfaces, and the proximal, medial, and distal regions of each gill. The collective data from 260 crabs were pooled for an analysis that showed a nonrandom relationship between the size of octolasmids and thier location within the gill chamber. On the inside gill surfaces O. angulata attained its largest average size on gills 3, 7, and 8, whereas on the o...