Effects of shell fit on the biology of the hermit crab Pagurus longicarpus (Say)

Abstract

Most hermit crabs have a specialized lifestyle that requires them to occupy gastropod shells. The size of shells that hermit crabs inhabit relative to their body size affects their growth, survival and fecundity. In this study, the effects of shell fit on individual growth rate, risk of predation, feeding rate, and activity level were examined in the laboratory for hermit crabs Pagurus longicarpus collected from Nahant, MA, USA. Feeding rate and general activity level of hermit crabs confined to tightly fitting shells and hermit crabs occupying shells of preferred size were not significantly different. Hermit crabs confined to tightly fitting shells grew at significantly slower rates, and were significantly more susceptible to predation by a common North Atlantic rock crab, Cancer irroratus. While this study provides further evidence of the negative effects of tight shell fit on growth and survivorship of hermit crabs, a mechanistic explanation for the decreased growth rate of hermit crabs in tightly fitting shells is still sought.