Hemolymph responses of Alaskan king crabs to rhizocephalan parasitism

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Abstract
Hemolymph from three king crab species, red (Paralithodes camtschatica), blue (P. platypus), and golden (Lithodes aequispina), parasitized by the rhizocephalan Briarosaccus callosus was examined for parasite-induced changes. Protein, hemoglobin, hemocyanin, and glucose concentrations, hemocyte counts, pH, osmolality, and hemolymph ion concentrations were measured. Parasite hemolymph was also examined. Effects on host hemolymph were decreased osmolality and sodium and chloride concentrations, and increased protein, hemocyanin, and glucose concentrations. Not all effects occurred in each host species. Correlations existed in some host species between number of externae and sodium and protein concentrations and shell condition. Protein electrophoregrams of parasitized and unparasitized crabs were similar. The red color of parasite hemolymph was due to hemoglobin averaging 5.8 mg/mL. No parasite hemoglobin was found in the host hemolymph. Electrophoregrams of parasite hemolymph from the three host species were similar. Hemocyanin was present in parasite hemolymph from red and golden king crab hosts. No significant difference in hemocyte count existed between parasitized and unparasitized blue king crabs. Red and golden king crabs exhibited a response that could explain their lower rates of parasitism and less frequent multiple infections, while blue king crabs had little defense against the parasite.

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