The association of Calliactis tricolor with its pagurid, calappid, and majid partners in the Caribbean

Abstract

Calliactis tricolor (Lesucur) lives most commonly in Puerto Rico as a commensal on Turbo and Fasciolaria shells, and less commonly on Murex shells inhabited by the pagurid Dardanus venosus. The partnership is less dependent on the response of the anemone to the shell than the European partnership between C. parasitica and D. arrosor. Besides D. venosus, which is active towards C. tricolor, another larger pagurid, Petrochirus diogenes, and the spider crab Stenocionops furcata display extremely effective behavior patterns in transferring the anemone. S. furcata may carry as many as 20 to 30 C. tricolor on its carapace and legs. When it encounters C. tricolor attached to another surface, S. furcata uses chelipeds and walking legs in stroking, scratching, and pinching movements, at first gently, then more actively, until the anemone is freed. After a period of manipulation, the crab seizes the anemone firmly in one cheliped and hoists it overhead to place it on the carapace. Both chelipeds usually test the carapace beforehand for free areas. C. tricolor relaxes completely when stimulated and manipulated in these various ways, apparently in a state of general inhibition. A calappid crab, Hepatus epheliticus, on which C. tricolor lives in the Gulf of Mexico, occasionally showed rearing and rubbing of carapace on the tentacles in response to C. tricolor. This led the anemone to transfer to the crab. C. tricolor also transferred to H. epheliticus without such activity by the crab. In discussing the results, the authors emphasized the variety of tactile stimuli used by different crabs. This is reflected in a flexible response pattern in the anemone. The behavioral capacities of S. furcata, in responding to C. tricolor and in placing it on the carapace, are thought to be remarkable for a crustacean.