Post-eclosion temperature effects on insect cuticular hydrocarbon profiles

The insect cuticle is the interface between internal homeostasis and the often harsh external environment. Cuticular hydrocarbons (CHCs) are key constituents of this hard cuticle and are associated with a variety of functions including stress response and communication. CHC production and deposition on the insect cuticle vary among natural populations and are affected by developmental temperature; however, little is known about CHC plasticity in response to the environment experienced following eclosion, during which time the insect cuticle undergoes several crucial changes. We targeted this crucial phase and studied post-eclosion temperature effects on CHC profiles in two natural populations of Drosophila melanogaster. A forty-eight hour post-eclosion exposure to three different temperatures (18, 25, & 30 °C) significantly affected CHCs in both ancestral African and more recently derived North American populations of D. melanogaster. A clear shift from shorter to longer CHCs chain-length was observed with increasing temperature, and the effects of post-eclosion temperature varied across populations and between sexes. The quantitative differences in CHCs were associated with variation in desiccation tolerance among populations. Surprisingly, we did not detect any significant differences in water loss rate between African and North American populations. Overall, our results demonstrate strong genetic and plasticity effects in CHC profiles in response to environmental temperatures experienced at the adult stage as well as associations with desiccation tolerance, which is crucial in understanding holometabolan responses to stress.

昆虫表皮（insect cuticle）是机体内部稳态与严酷外部环境之间的界面。表皮碳氢化合物（Cuticular hydrocarbons, CHCs）是该硬质表皮的关键组成成分，与应激响应、信息通讯等多种生理功能密切相关。表皮碳氢化合物的合成与沉积在不同自然种群间存在差异，且受发育阶段温度的影响；然而，学界对于羽化后环境所引发的表皮碳氢化合物可塑性尚知之甚少——此阶段昆虫表皮会经历多项关键变化。本研究聚焦这一关键阶段，以两个自然种群的黑腹果蝇（Drosophila melanogaster）为研究对象，探究了羽化后温度对其表皮碳氢化合物谱的影响。将羽化后48小时的果蝇分别置于18、25、30℃三种温度下暴露48小时，结果显示，黑腹果蝇的祖先类群非洲种群与近年衍生的北美种群的表皮碳氢化合物谱均发生了显著变化。随着温度升高，表皮碳氢化合物的碳链长度呈现出从短到长的显著偏移，且羽化后温度的影响效应因种群和性别不同而存在差异。表皮碳氢化合物的数量差异与不同种群间的耐旱性变异存在关联。令人意外的是，本研究未检测到非洲种群与北美种群在水分流失速率上存在显著差异。总体而言，本研究结果表明，成虫阶段所经历的环境温度会对表皮碳氢化合物谱产生强烈的遗传效应与可塑性效应，且该效应与耐旱性存在关联——这一发现对于理解全变态昆虫的应激响应机制至关重要。