Cuticular Water Pump in Insects

Abstract

AMONG the ways in which terrestrial arthropods can control their environmental water relations, the active retention of water¹, the regulation of water loss², and the active uptake of atmospheric water³ have been found to be concerned with the movement of water through the cuticle. All these phenomena imply a water pump associated with the cuticle and the most satisfactory mechanism so far proposed is based on an active process which reduces the water content of the solid cuticle to a level below that which would be in equilibrium with the blood⁴. If the gradient of water activity between atmosphere and inner cuticle across the epicuticular wax layer can be increased, retention, regulation or active uptake will be a consequence of the new conditions thus established. The body of evidence for a water pump makes it clear that, if reduction of cuticular water-content is a part of the mechanism, it should be sufficiently large to be demonstrable. This communication reports preliminary results of an investigation of the possibility of a water pump in the cuticle of two species of insect, the cockroach Periplaneta americana and the locust Locusta migratoria.