GHERARDI, F; ATEMA, J; Univ. of Florence, Italy; BUMP, Woods Hole, Ma: Individual recognition in hermit crabs: learning and forgetting the opponent�s identity

One mechanism that permits the maintenance of dominance hierarchies is individual recognition, that is the ability of an animal to recognize a conspecific on the basis of one or more identifying cues. Our objective here was to examine the potential of the long-clawed hermit crab, Pagurus longicarpus, to differentiate between familiar and unfamiliar opponents, following in part the protocol used by Karavanich and Atema (1998) for the American lobster. Results showed that the agonistic level of hermit crabs was higher in unfamiliar than in familiar pairs; in addition, betas were more prone to initiate an interaction with unfamiliar than with familiar alphas. The identity of the opponent was acquired in 30 min of interaction and its memory lasted for four, but not six, days of isolation. Hermit crabs still remember the former opponent when separated from it for one day while housed with other five hermit crabs. Further studies are needed to clarify the proximate and ultimate causes of this phenomenon in hermit crabs. Acknowledgments: Funds were provided to F.G. by MBL Associates, Ann E. Kammer Memorial Fellowship Fund, H. Keffer Hartline Fellowship Fund, Frank R. Lillie Fund, Plum Foundation.