Temporal shifts in insect cuticular hydrocarbons in response to experimental desiccation.

Insects are vulnerable to desiccation as they are small and have a high surface area-to-volume ratios. Over 80% of their body water is lost through the cuticle, but insects possess specialised cells that synthesize cuticular hydrocarbons (CHCs) to form a hydrophobic waxy barrier that reduces water loss. However, how rapidly CHCs are synthesized and transported across the cuticle under desiccating conditions remains poorly understood. To examine this, we exposed male Drosophila melanogaster to varying desiccation durations (2, 4, 6, 8, and 10 h) and compared CHC profiles for each of these time-points to an experimental control (no desiccation: 0 h). We found a rapid, time-dependent shift in CHC composition, marked by an early increase in short-chain hydrocarbons followed by enrichment of longer chain, methyl-branched CHCs over longer periods of desiccation exposure. Cumulative water loss increased most sharply within the first 2 h of desiccation and then progressed more slowly from 2 to 8 h before rising again at 10 h. These changes were closely mirrored by temporal shifts in CHC composition, suggesting that CHCs are dynamic and respond rapidly to desiccation stress.