Detachment of Sea Anemones by Commensal Hermit Crabs and by Mechanical and Electrical Stimuli

Abstract

THE ability of some hermit crabs to detach commensal sea anemones and place them on their shells has interested ecologists and ethologists for many years¹. Anemones belonging to the genus Calliactis are perhaps best known in this respect. Excellent accounts of the behaviour of the Mediterranean hermit crab Dardanus (= Pagurus) arrosor Herbst, towards C. parasitica (Couch) have long been available^2,3. Ross⁴ showed that Pagurus bernhardus (L.) which lives with C. parasitica in the English Channel has no behaviour pattern in relation to the anemone. C. parasitica has its own behaviour pattern triggered by a chemical factor in the gastropod shell occupied by the pagurid and the anemone is able to transfer to the shell without help from the crab. Ross and Sutton⁵ have also shown that the success of D. arrosor in transferring Calliactis to its shells depends on the simultaneous occurrence of the anemone's behaviour pattern in response to the shell; they emphasized the co-operative roles of both partners in establishing the association.