title: Behavioral evidence illuminating the visual abilities of the terrestrial Caribbean hermit crab Coenobita clypeatus.
abstract: Hermit crabs hide into shells when confronted with potential dangers, including images presented on a monitor. We do not know, however, what hermit crabs can see and how they perceive different objects. We examined the hiding response of the Caribbean hermit crab (Coenobita clypeatus) to various stimuli presented on a monitor in seven experiments to explore whether crabs could discriminate different properties of a threatening digital image, including color, brightness, contrast, shape and orientation. We found crabs responded differently to expanding circles presented in wavelengths of light corresponding to what humans see as red, blue, and green. "Blue" stimuli elicited the strongest hiding response (Experiments 1, 2, & 7). "Blue" was also more effective than a gray stimulus of similar brightness (Experiment 3). Hermit crabs were sensitive to the amount of contrast between a stimulus and its background rather than absolute brightness of the stimulus (Experiment 4). Moreover, we did not find evidence that crabs could discriminate orientation (Experiment 6), and mixed evidence that they could discriminate stimulus shape (Experiments 5 & 7). These results suggest that the Caribbean hermit crab is sensitive to color features, but not spatial features, of a threatening object presented on a computer screen. This is the first study to use the hiding response of the hermit crab to examine its visual ability, and demonstrates that the hiding response provides a useful behavioral approach with which to study learning and discrimination in the hermit crab.
authors.affiliation: Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China; Department of Psychology, University of California, Los Angeles, USA.
authors.forename: Xiaoge
authors.initials: X
authors.lastname: Ping
authors.affiliation: Department of Psychology, University of California, Los Angeles, USA.
authors.forename: Ji Sun
authors.initials: JS
authors.lastname: Lee
authors.affiliation: Department of Psychology, University of California, Los Angeles, USA.
authors.forename: Dennis
authors.initials: D
authors.lastname: Garlick
authors.affiliation: Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Jiang
authors.affiliation: Department of Psychology, University of California, Los Angeles, USA. Electronic address: blaisdell@psych.ucla.edu.
authors.forename: Aaron P
authors.initials: AP
authors.lastname: Blaisdell
mesh_terms: D000818:Animals; D033381:Anomura / Q000502:physiology*; D000067290:Behavior Rating Scale; D001522:Behavior, Animal / Q000502:physiology; D017691:Caribbean Region; D010775:Photic Stimulation; D014785:Vision, Ocular / Q000502:physiology
keywords: Color; Discrimination; Habituation; Hiding response; Shape; Threat detection