The evaporation of water from Helix aspersa. IV. Loss from the mantle of the inactive snail.

When a snail withdraws into its shell the only parts of the body left exposed to the air are a number of fleshy extensions of the mantle; the so-called mantle collar. This area of the body is a potentially serious source of water loss in the inactive terrestrial snail. The evaporation of water from active specimens of the common garden snail, Helix aspersa, is nearly identical to that from a free water surface (Machin, 1964a). However, preliminary findings (Machin, 1965) indicate that the rate of evaporation from the exposed surface of the mantle is reduced following withdrawal of the snail to the inactive state. That this species of snail is able to ' regulate' evaporation is of considerable physiological and ecological importance. The present work represents a critical examination of the physiological mechanisms which operate to modify water evaporation from the exposed integument of inactive snails.