Abstract
A flexible body image is required by animals if they are to adapt to body changes and move effectively within a structurally complex environment. Here, we show that terrestrial hermit crabs, Coenobita rugosus, which frequently change shells, can modify walking behaviour, dependent on the shape of the shell. Hermit crabs walked along a corridor that had alternating left and right corners; if it was narrow at the corner, crabs rotated their bodies to avoid the wall, indicating an awareness of environmental obstacles. This rotation increased when a plastic plate was attached to the shell. We suggest that the shell, when extended by the plate, becomes assimilated to the hermit crab's own body. While there are cases of a tool being assimilated with the body, our result is the first example of the habitat where an animal lives and/or carries being part of a virtual body.
Highlights
Animals must adapt and control their changing bodies, e.g. when a deer re-grows antlers
Hermit crabs walked along a corridor that had alternating left and right corners; if it was narrow at the corner, crabs rotated their bodies to avoid the wall, indicating an awareness of environmental obstacles
We suggest that the shell, when extended by the plate, becomes assimilated to the hermit crab’s own body
Summary
Animals must adapt and control their changing bodies, e.g. when a deer re-grows antlers. The phenomenon has been investigated in humans with the rubber hand illusion and in animals by examining how they use tools as extensions of their body [1] In both cases, new parts are accepted as being their own and under their own control [2]. Using tools (or other constructions [3]) as extensions of the body may have consequences for perception and cognition, as the object becomes embedded as an integrated functional body component, a process known as embodiment [2,4,5]. This may be exemplified by learning to drive a car. Full comprehension of the car body (whole body) occurs dynamically when steering the car between obstacles
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