MEPS 170:215-229 (1998)  -  doi:10.3354/meps170215

Prevalences of parasitized and hyperparasitized crabs near South Georgia

George Watters*

U.S. AMLR Program, NOAA Fisheries, PO Box 271, San Diego, California 92038, USA
*Present address: Inter-American Tropical Tuna Commission, 8604 La Jolla Shores Drive, La Jolla, California 92037, USA. E-mail:

ABSTRACT: This study identifies sources of variation in the prevalences of parasitized and hyperparasitized Paralomis spinosissima, a lithodid found around South Georgia. The parasite is Briarosaccus callosus, a rhizocephalan; the hyperparasite is an undescribed liriopsinine. Generalized additive models were used to model data collected during 1992 and 1995. Parasites were less prevalent on female crabs and most prevalent in submarine canyons. The former effect may be due to sex-specific differences in gill cleaning behavior, and the latter effect may result from reduced gill cleaning efficiency in areas where the seafloor is covered with fine sediment. The size-prevalence curve was dome-shaped; this probably indicates that B. callosus reduces the growth rate and increases the mortality rate of P. spinosissima. Parasite prevalence decreased with increasing crab density but increased with increasing parasitized crab density. These results suggest that parasitized crabs do not aggregate with unparasitized males. Habitat was a significant source of variation in hyperparasite prevalence during 1992 but not 1995. Between-year comparisons of parasite and hyperparasite prevalences were equivocal and failed to provide convincing evidence against parameter stationarity and stability in the P. spinosissima-B. callosus-liriopsinine system.

KEY WORDS: Lithodid crabs · Rhizocephalan barnacles · Cryptoniscid isopods · Parasitism · Hyperparasitism · Prevalence · Generalized additive models

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