Parasitism of the Rhizocephalan Briarosaccus callosus on the Crab Paralomis verrilli (Crustacea: Lithodidae) in the Waters of Southeast Sakhalin

摘要

The crab Paralomis verrilli in the waters of southcast Sakhalin is infected by the parasitic rhizocephalan barnacle Briarosaccus callosus. The prevalence of parasitic infection was on the average 4.36% (6.29% for females, 3.28% for males) and varied between samples from none up to 14.9%. The degree of prevalencc was not related to the average carapace width and the scx ratio of crabs in samples. Sterilization of female P. verrilli was caused by the B. callosus infestation or its consequences. No more than two parasite exter-nae per crab were found. Crabs with two externae made up 5.6% of all infected specimens. The infestation of crab hosts with two B. callosus externae negatively influenced the growth of the externae. A positive relationship was found between the width of the crab carapace and the length of the parasitic externae. The survival rate of P. verrilli with either one or two parasite B. callosus externae did not differ substantially. The proportion of crabs with externae and those with "scars" (12.2% in our case) can be taken as the index of survival of the parasitized crabs.