To survive adverse environments, many animals enter a dormant state such as hibernation, dauer, or diapause. Various Drosophila species undergo adult reproductive diapause in response to cool temperatures and/or short day-length. While flies are less active during diapause, it is unclear how adverse environmental conditions affect circadian rhythms and sleep. Here we show that in diapause-inducing cool temperatures, Drosophila melanogaster exhibit altered circadian activity profiles, including severely reduced morning activity and an advanced evening activity peak. Consequently, the flies have a single activity peak at a time similar to when nondiapausing flies take a siesta. Temperatures ≤15 °C, rather than photoperiod, primarily drive this behavior. At cool temperatures, flies rapidly enter a deep-sleep state that lacks the sleep cycles of flies at higher temperatures and require high levels of stimulation for arousal. Furthermore, we show that at 25 °C, flies prefer to siesta in the shade, a preference that is virtually eliminated at 10 °C. Resting in the shade is driven by an aversion to blue light that is sensed by Rhodopsin 7 outside of the eyes. Flies at 10 °C show neuronal markers of elevated sleep pressure, including increased expression of Bruchpilot and elevated Ca 2+ in the R5 ellipsoid body neurons. Therefore, sleep pressure might overcome blue light aversion. Thus, at the same temperatures that cause reproductive arrest, preserve germline stem cells, and extend lifespan, D. melanogaster are prone to deep sleep and exhibit dramatically altered, yet rhythmic, daily activity patterns.

中文翻译：

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黑腹果蝇滞育期间昼夜节律、睡眠和视紫质 7 依赖性遮荫偏好的改变


为了在恶劣的环境中生存，许多动物进入休眠状态，例如冬眠、滞育或滞育。各种果蝇物种都会因低温和/或短日照而经历成虫生殖滞育。虽然果蝇在滞育期间不太活跃，但尚不清楚不利的环境条件如何影响昼夜节律和睡眠。在这里，我们发现，在滞育引起的凉爽温度下，果蝇表现出昼夜节律活动特征的改变，包括早晨活动严重减少和晚间活动高峰提前。因此，果蝇在同一时间有一个活动峰值，类似于非滞育果蝇午睡的时间。导致这种行为的主要因素是温度≤15°C，而不是光周期。在凉爽的温度下，果蝇迅速进入深度睡眠状态，该状态缺乏果蝇在较高温度下的睡眠周期，并且需要高水平的刺激才能唤醒。此外，我们发现，在 25°C 时，苍蝇更喜欢在阴凉处午睡，而在 10°C 时，这种偏好几乎被消除。在阴凉处休息是由于眼睛外部的视紫红质 7 感觉到对蓝光的厌恶。 10 °C 的果蝇显示出睡眠压力升高的神经元标志物，包括 R5 椭球体神经元中 Bruchpilot 表达增加和 Ca 2+ 升高。因此，睡眠压力可能会克服蓝光厌恶。因此，在导致繁殖停滞、保存生殖干细胞和延长寿命的相同温度下，黑腹果蝇容易进入深度睡眠，并表现出显着改变但有节奏的日常活动模式。