Water vapour sorption by the pedal mucus trail of a land snail

The hydrophilicity of pedal mucus trails deposited by snails influences the settlement of marine organisms and can potentially influence the trailing and homing mechanisms of terrestrial snails. The composition of pedal mucus deposited as a trail on a solid substrate by the giant African land snail (Achatina marginata) has been probed non-invasively using infrared ellipsometry. The primary chemical groups in the mucus (in its native state) have been identified through their characteristic infrared absorption frequencies. Water vapour sorption in the mucus trails in equilibrium with the atmosphere was measured as a function of the relative humidity (RH). When RH = 84%, the mucus contains 53 volume percent water. The water sorption isotherm of the mucus trail can be described through a Flory-Huggins polymer/solvent interaction parameter of chi = 0.54 +/- 0.1, which is comparable to the value for some synthetic hydrophilic polymers, such as poly(vinyl pyrrolidone). (C) 2003 Elsevier B.V. All rights reserved.