PREVALENCES OF PARASITIZED AND HYPERPARASITIZED CRABS NEAR SOUTH GEORGIA

This study identifies sources of variation in the prevalences of paras itized and hyperparasitized Paralomis spinosissima, a lithodid found a round South Georgia. The parasite is Briarosaccus callosus, a rhizocep halan; the hyperparasite is an undescribed liriopsinine. Generalized a dditive models were used to model data collected during 1992 and 1995. Parasites were less prevalent on female crabs and most prevalent in s ubmarine canyons. The former effect may be due to sex-specific differe nces in gill cleaning behavior, and the latter effect may result from reduced gill cleaning efficiency in areas where the seafloor is covere d with fine sediment. The size-prevalence curve was dome-shaped; this probably indicates that B, callosus reduces the growth rate and increa ses the mortality rate of P. spinosissima. Parasite prevalence decreas ed with increasing crab density but increased with increasing parasiti zed crab density. These results suggest that parasitized crabs do not aggregate with unparasitized males. Habitat was a significant source o f variation in hyperparasite prevalence during 1992 but not 1995. Betw een-year comparisons of parasite and hyperparasite prevalences were eq uivocal and failed to provide convincing evidence against parameter st ationarity and stability in the P. spinosissima-B, callosus-liriopsini ne system.