Protection of Hermit Crabs (Dardanus spp.) from Octopus by Commensal Sea Anemones (Calliactis spp.)

Abstract

PARTNERSHIPS between sea anemones and hermit crabs have long been considered as examples of commensal associations that seem to benefit both partners. In some of these partnerships the pagurid shows no behaviour pattern towards the anemone (Pagurus bernhardus (L.) and Calliactis parasitica (Couch)¹). In these associations the crab probably receives no benefit, all gain going to the anemone which, by clinging to the shell and transferring itself to it, has the advantage of being transported. In most cases, however, especially those involving Dardanus spp., the pagurids actively transfer their commensal anemones to their shells^2–5; in these associations the crab could be expected to benefit in some way. Camouflage, assistance in capturing prey, protection from predators and cover for weak shells have all been suggested as possible gains for pagurids that carry anemones, but there has been little direct evidence to support any of these possibilities⁶.