Cuticular lipids and water balance

Abstract

Epicuticular lipids serve many roles in insects and other terrestrial arthropods (see other chapters in this volume), but the first to be recognized was as a barrier to transpiration through the surface of the animal. Surface-area to volume ratios increase as size decreases, so that smaller animals become increasingly susceptible to dehydration. Künelt (1928; cited by Wigglesworth, 1933) noted the presence of hydrophobic substances on the insect cuticle and proposed that these reduce water-loss. Their importance in water conservation is made apparent by the fact that even a brief treatment with organic solvents to remove surface lipids can result in water-loss rates increasing 10–100 fold (Hadley, 1994). On the other hand, water can be lost via other routes. These losses can be substantial (e.g. bloodsucking insects excrete huge amounts of fluid after a meal). Thus, under certain conditions, cuticular waterproofing may be a minor part of the overall water budget.