Occurrence and distribution of invertebrate epizoites on the Rock Crab, Cancer Irroratus say from the Northumberland Strait, New Brunswick

Abundance and species distributions of invertebrate epizoites of Cancer irroratus Say were examined. A numerical technique for recording the location of epizoites upon the crab shell was devised. Cancer irroratus supported a total of 53 species. Ectoprocts, coelenterates and polychaetes were dominant phyla in terms of numbers of species, while bryozoans, hydroids, bivalves and tunicates were the four major taxa in terms of numbers of crabs colonized. Spirorbid worms, barancles, gastropods, amphipods and limpets were the six minor taxa that were recorded but were not sufficiently abundant (<2%) to justify further analysis. Fifty-eight percent of male and 76 percent of female Cancer irroratus had one or more epizoic taxa. Individual males supported as many as six taxa and females had up to three. Male crabs were significantly larger than females and a direct relationship between size of crab and percent of crabs colonized was found. Temporal abundance patterns of the four major epizoic taxa reflected the moulting biology of Cancer irroratus. Microdistributions of the 23 epizoic species examined in detail were influenced by the presence or absence of Setae on regions of the shell. The setae are considered to serve a structural function analogous to sessile organisms of the general fouling community, in that they insure a buildup of detritus and provide a substrate suitable for the establishment of motile species.