How hermit crabs adapt to a new 'home'

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Hermit crabs treat the shell they inhabit as an extension of their body, according to a new study.

In research to be published in a forthcoming issue of the journal Biology Letters, Kohei Sonoda and co-authors found that terrestrial hermit crabs (Coenobita rugosus) can modify their walking behaviour according to the shape of the shell they inhabit.

Studying crabs from Okinawa, the authors glued plastic plates in asymmetrical positions on the shells of the crabs, before observing their progress along a corridor with alternating left- and right-hand turns.

Although the crabs seemed out of balance initially, they rapidly adapted to their new, more awkward shape rapidly and in under 20 seconds, they were able to modify the way they walked and increase their turning angle when going around corners to accommodate their new shape.

The authors think that the crabs were able to modify their balance by altering their leg positions and posture within the shell.

"This suggests that the shell, when extended by the plate becomes assimilated to the hermit crab's own body,” says Yukio Gunji, one of the authors.

For more information, see the paper: Sonoda, K, A Asakura, M Minoura, RW Elwood and Y-P Gunji (2012) Hermit crabs perceive the extent of their virtual bodies. Biology Letters doi:10.1098/rsbl.2012.0085.

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