ABSTRACT
Moist-skinned terrestrial animals such as snails and slugs are highly susceptible to desiccation. It has been shown that active slugs can lose up to 35% of their initial body weight (%IBW) within 2-3 h (Dainton, 1954; Prior, Hume, Varga & Hess, 1983). They can, however, rapidly recover from dehydration by integumental absorption of water while in contact with a moist substrate (Burton, 1966; Prior, 1982, 1984). This process of contact-rehydration involves an increase in the epithelial paracellular permeability of the foot and is mediated by a well regulated behavioural sequence (Prior, 1982, 1984; Prior & Uglem, 1984). Contact-rehydration is initiated when slugs have been dehydrated to the threshold level of 60–70% IBW. They move onto a moist surface and assume a characteristic flattened posture while water is absorbed through the foot. They remain in this posture until enough water has been absorbed to achieve their rehydration set-point (93·6 ± 12·2% IBW for Limax maximus;Prior, 1984). Once rehydrated, the slugs move off the moist surface and come to rest on a dry surface, thus terminating the behaviour.
