Association of the Hermit Crab Pagurus Longicarpus Say, 1817, With Symbiotic Hydroids: Consequences of Predation By Lobsters

Abstract

Previous studies indicate that symbiotic hydroids of the genus Hydractinia protect hermit crabs from certain predators, but have little effect on others. Laboratory experiments were performed to elucidate the relationship between the long-clawed hermit crab, Pagurus longicarpus, and its symbiotic hydroid, Hydractinia symbiolongicarpus, in environments with and without a predator, the lobster Homarus americanus. Hydroids did not protect P. longicarpus from predation by H. americanus. P. longicarpus escaped predation by burrowing into the sand or fleeing. The presence of H. americanus had no effect on the preference of P. longicarpus for hydroid-covered shells, further supporting the hypothesis that H. symbiolongicarpus does not protect P. longicarpus from predation by H. americanus. Overall, P. longicarpus showed no preference for shells with or without hydroids, suggesting that the costs of associating with hydroids roughly equal the benefits.