Behavioral evidence illuminating the visual abilities of the terrestrial Caribbean hermit crab Coenobita clypeatus

Abstract

a b s t r a c tHermit 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.

Peer Review #2 of "Hermit crab response to a visual threat is sensitive to looming cues (v0.1)"

“…For example, evidence is mixed as to whether pigeons (Columba livia) can perceive the pictorial or representational aspects of pictorial displays (Fagot, 2000). We've found evidence that the Caribbean hermit crab lacks color vision (Ping et al, 2015). Unpublished studies from our lab also fail to find evidence that hermit crabs can distinguish between pictorial content that is naturalistic (e.g., photographs of a hawk, coconut crab, sea gull), man-made real objects (e.g., a…”

“…Caribbean terrestrial hermit crabs (Coenobita clypeatus) are an ideal invertebrate system to test looming image discrimination and processing. Prior work in our lab demonstrated that hermit crabs have a binary escape response; they hide (or fail to hide) in their shells when presented with a looming image of a predator or geometric shape presented on a computer screen (Chan et al 2010b;Ping et al, 2015;Ryan et al 2012;Stahlman et al 2011;Watanabe et al 2012).…”

Doors to the Homes: Signal Potential of Red Coloration of Claws in Social Hermit Crabs

“…A key criterion for a signal, including a signal of RHP, is that recipients must be able to perceive and hence respond to the signal ( Searcy and Nowicki 2005 ; Bradbury and Vehrencamp 2011 ; Laidre and Johnstone 2013 ). Interestingly, laboratory experiments in terrestrial hermit crabs have revealed that individuals can differentiate artificial red coloration from blue and green coloration ( Ping et al. 2015 ).…”

Hermit crab response to a visual threat is sensitive to looming cues

“…For example, evidence is mixed as to whether pigeons ( Columba livia ) can perceive the pictorial or representational aspects of pictorial displays ( Fagot, 2000 ). We’ve found evidence that the Caribbean hermit crab lacks color vision ( Ping et al, 2015 ). Unpublished studies from our lab also fail to find evidence that hermit crabs can distinguish between pictorial content that is naturalistic (e.g., photographs of a hawk, coconut crab, sea gull), man-made real objects (e.g., a picture of a couch), and simple geometric shapes (e.g., a square, star, or oval).…”

“…Caribbean terrestrial hermit crabs (Coenobita clypeatus ) are an ideal invertebrate system to test looming image discrimination and processing. Prior work in our lab demonstrated that hermit crabs have a binary escape response; they hide (or fail to hide) in their shells when presented with a looming image of a predator or geometric shape presented on a computer screen ( Chan et al, 2010b ; Ping et al, 2015 ; Ryan et al, 2012 ; Stahlman et al, 2011 ; Watanabe et al, 2012 ).…”