Elevated sleep quota in a stress-resilient Drosophila species

Sleep is broadly conserved across the animal kingdom but can vary widely between species. It is currently unclear which selective pressures and regulatory mechanisms influence differences in sleep between species. The fruit fly Drosophilamelanogaster has become a successful model system for examining sleep regulation and function, but little is known about the sleep patterns in many related fly species. Here, we find that fly species with adaptations to extreme desert environments, including D. mojavensis, exhibit strong increases in baseline sleep compared to D. melanogaster. Long-sleeping D. mojavensis show intact homeostasis, indicating that desert flies carry an elevated drive for sleep. In addition, D. mojavensis exhibit altered abundance or distribution of several sleep/wake related neuromodulators and neuropeptides that are consistent with their reduced locomotor activity and increased sleep. Finally, we find that in a nutrient-deprived environment, the sleep patterns of individual D. mojavensis are strongly correlated with their survival time and that disrupting sleep via constant light stimulation renders D. mojavensis more sensitive to starvation. Our results demonstrate that D. mojavensis is a novel model for studying organisms with high sleep drive, and for exploring sleep strategies that provide resilience in extreme environments.

睡眠在动物界中广泛保守，但不同物种间的睡眠模式差异显著。目前尚不清楚是哪些选择压力与调控机制影响了不同物种间的睡眠差异。黑腹果蝇（Drosophila melanogaster）已成为研究睡眠调控与功能的经典模式生物，但目前对诸多近缘果蝇物种的睡眠模式仍知之甚少。本研究发现，适应极端沙漠环境的果蝇物种（包括莫哈韦果蝇（Drosophila mojavensis）），其基础睡眠时长相较于黑腹果蝇显著增加。睡眠时长更长的莫哈韦果蝇保留了完整的睡眠稳态调节能力，这表明沙漠果蝇拥有更高的睡眠驱动水平。此外，莫哈韦果蝇体内多种与睡眠-觉醒相关的神经调质和神经肽的丰度或分布发生了改变，这与其运动活性降低、睡眠时长增加的表型相一致。最后，本研究发现，在营养匮乏的环境中，单只莫哈韦果蝇的睡眠模式与其存活时长显著相关；而通过持续光照干预睡眠的实验则表明，睡眠干扰会使莫哈韦果蝇对饥饿更为敏感。本研究结果证实，莫哈韦果蝇可作为研究高睡眠驱动生物的新型模式生物，同时也为探索极端环境下赋予生物适应性的睡眠策略提供了新的研究模型。