The Physical Properties of the Pedal Mucus of the Terrestrial Slug, Ariolimax Columbianus

ABSTRACT The pedal mucus of gastropods functions in locomotion by coupling the movements of the foot to the substratum. The pedal mucus of the terrestrial slug, Ariolimax columbianus, is suited to this role by the following unusual physical properties. At small deformations the mucus is a viscoelastic solid with a shear modulus of 100–300 Pa. The mucus shows a sharp yield point at a strain of 5–6, the yield stress increasing with increasing strain rate. At strains greater than 6 the mucus is a viscous liquid (η = 30–50 poise). The mucus recovers its solidity if allowed to ‘heal’ for a period of time, the amount of solidity recovered increasing with increasing time.