PARASITES AND SYMBIONTS OF THE CRAB POR TUNUS PELAGICUS FROM

Fifteen parasites and symbionts were found in the tissues, in the branchial chambers, and on external surfaces of the sand crab Portunus pelagicus. Female crabs possessed more species of parasites and symbionts, and had a more specialized fauna than did male crabs. Females also had a higher prevalence of the peritrich ciliate Operculariella sp., a tetraphyllidean cestode, and the barnacles Octolasmis spp. Juvenile crabs had fewer parasites than mature crabs, being regularly colonized by only 2 parasites (the lecanicephalid cestode Polypocephalus moretonensis and the microphallid trematode Levinseniella sp.), and 2 symbionts (the barnacles Octolasmis spp. and Chelonibia patula). There were positive correlations between intensity of infection and host size (carapace width) for only 1 parasite and 2 symbionts (P. moretonensis, the nemertean Carcinonemertes mitsukurii, and Octolasmis spp., respectively). Not surprisingly, the molt condition of the crab influenced the abundances of the sessile external symbionts. Crabs in the postmolt condition had fewer Operculariella sp., C. patula, and Octolasmis spp. The abundances of the motile Carcinonemertes mitsukurii and the internal parasites and symbionts were not, however, affected by the molt condition of their hosts.