The shadow of the shell: a cue for a new home

Abstract

AbstractHermit crabs use different senses to search for and find shells. In most cases, chemical cues have been proven to act as a very efficient way of finding new shells. However, in intertidal environments, the water transports chemical signals in different directions and velocities may make it harder to track the source of the cue, so visual stimuli may be a more precise source of information. The hermit crabCalcinus californiensisshows a preference for the biconical shells ofStramonita biserialis, although the crabs may also use the less preferred shell ofNerita scabricosta. We were interested in exploring ifC. californiensisidentify the preferred shell species through vision in the absence of chemical stimuli. We presented both shell species to hermit crabs in two different sets of experiments. In one experiment, we presented to the hermit crabs real shells ofN. scabricostaandS. biserialis, and in another, we presented only the silhouettes of the same shells. The hermit crabs discriminated between the real shells and the silhouettes ofN. scabricostaandS. biserialis. Females attended with higher frequency to real shells and silhouettes ofS. biserialis; while males attended more to shells and silhouettes ofN. scabricosta. Although, larger males biased their attendance toward shells ofS. biserialis. Our results show that visual perception may be more important than we have thought in intertidal animals.