Bryozoan colonization of the marine isopod Glyptonotus antarcticus at Signy Island, Antarctica

Sixty specimens of the giant marine isopod Glyptonotus antarcticus Eights, collected from Borge Bay, Signy Island, Antarctica were examined for epizoa ns. Ten species of cheilostomatid bryozoans were found on the isopods. The purpose of the study was to quantify the prevalence, intensity, abundance, and spatial distribution of the bryozoans on the isopods. The proportion of isopods colonized was 42%. The larger isopods had both significantly more epizoic bryozoan colonies and species. The greatest density of bryozoans wa s on the fused pleon and telson. There was no significant difference betwee n the dorsal and ventral abundance of bryozoan colonies. The diversity of e pizoic bryozoans on the isopods is higher than on other host organisms from more stable environments. This may be because of active selection by settl ing larvae. The frequency of local substrata bring scoured by ice is high a round Signy Island, so there may be a selective advantage in colonizing a m otile host.