CHEMICAL-DETECTION AND HOST SELECTION BY THE SYMBIOTIC CRAB PORCELLANA-SAYANA

The porcellanid crab Porcellana sayana is usually found associated wit h gastropod snails or hermit crabs that occupy gastropod shells. In th is study, we examined chemical mediation and host selection by P. saya na collected from hermit crabs. Chemical detection tests were done in a four-chamber choice apparatus. Odors tested were from the co-occurri ng symbiotic sea anemone Calliactis tricolor, the non-symbiotic anemon e Aiptasia pallida, the hermit crab Dardanus venosus, and the gastropo d snail Polinices duplicatus. In addition to odors from live animals, frozen and thawed snail muscle was tested. P. sayana was attracted che mically only to C. tricolor. In host selection tests involving sea ane mones and gastropod shells, P. sayana chose C. tricolor over shells, b ut chose shells over A. pallida. When given no other choice, P. sayana still avoided the non-symbiotic anemone while readily going to C. tri color in separate trials. Apparently, a symbiosis between P. sayana an d C. tricolor has ensued from the porcellanid/hermit crab association.