Plasticity of shell preference and its antipredatory advantages in the hermit crabCalcinuscaliforniensis

Abstract

The preference of the hermit crab Calcinus californiensis Bouvier, 1898 among six shell species and different shell sizes was evaluated in the presence of the swimming crab Arenaeus mexicanus (Gerstaecker, 1856), a natural predator of this species. In a second experiment, the survival benefit of the shell choice made under predation threat was examined by exposing hermit crabs occupying three different shell species (including the most and least preferred shells of two fits) to a free swimming crab predator. The preference for shell species was similar in the absence and presence of the predator threat, although the hermit crabs choose larger shells (loose) when exposed to the predator compared with the ones chosen in its absence. The predatory experiment showed a higher survival chance for the hermit crabs occupying loose shells of the preferred shell species (Cantharus sanguinolentus (Duclos, 1833)). The results of this study show that the hermit crab C. californiensis is able to change their preference for shell size in response to a predation threat and that the change in preference confers survival benefits for hermit crabs. This study is consistent with the assumption that predation is an important selective pressure for intertidal hermit crabs.