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Orientation of the hermit crab Clibanarius antillensis: Effects of visual and chemical cues

Abstract:

Orientation of the hermit crabs Clibanarius antillensis to solid and striped targets of different visual angles was tested in a circular arena upon exposure to background sea water, calcium concentrations, gastropod odor, predatory fish odor, and seagrass odor. The test hypotheses were that (1) this hermit crab has the capacity to use visual cues for orientation and (2) it discriminates between objects on the basis of visual and chemical information. Adult crabs were tested during the day without their gastropod shells, and orientation varied with concentration and chemical cue. In general, orientation increased as concentration increased up to a maximum orientation response and then declined at higher concentrations. Solid targets representing gastropod shells attracted crabs in the presence of calcium and gastropod odor. Orientation toward striped targets representing seagrass increased in the presence of seagrass odor. Finally, orientation directly away from a target (predator avoidance response) was only observed in the presence of predator odor. Thus, both hypotheses were supported.