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Drosophila ezoanauses an hour-glass or highly damped circadian clock for measuring night length and inducing diapause
Physiological Entomology ( IF 1.5 ) Pub Date : 2016-09-08 , DOI: 10.1111/phen.12165
Koustubh M Vaze 1 , Charlotte Helfrich-Förster 1
Affiliation  

Insects inhabiting the temperate zones measure seasonal changes in day or night length to enter the overwintering diapause. Diapause induction occurs after the duration of the night exceeds a critical night length (CNL). Our understanding of the time measurement mechanisms is continuously evolving subsequent to Bünning's proposal that circadian systems play the clock role in photoperiodic time measurement (Bünning, 1936). Initially, the photoperiodic clocks were considered to be either based on circadian oscillators or on simple hour‐glasses, depending on ‘positive’ or ‘negative’ responses in Nanda–Hamner and Bünsow experiments (Nanda & Hammer, 1958; Bünsow, 1960). However, there are also species whose responses can be regarded as neither ‘positive’, nor as ‘negative’, such as the Northern Drosophila species Drosophila ezoana, which is investigated in the present study. In addition, modelling efforts show that the ‘positive’ and ‘negative’ Nanda–Hamner responses can also be provoked by circadian oscillators that are damped to different degrees: animals with highly sustained circadian clocks will respond ‘positive’ and those with heavily damped circadian clocks will respond ‘negative’. In the present study, an experimental assay is proposed that characterizes the photoperiodic oscillators by determining the effects of non‐24‐h light/dark cycles (T‐cycles) on critical night length. It is predicted that there is (i) a change in the critical night length as a function of T‐cycle period in sustained‐oscillator‐based clocks and (ii) a fixed night‐length measurement (i.e. no change in critical night length) in damped‐oscillator‐based clocks. Drosophila ezoana flies show a critical night length of approximately 7 h irrespective of T‐cycle period, suggesting a damped‐oscillator‐based photoperiodic clock. The conclusion is strengthened by activity recordings revealing that the activity rhythm of D. ezoana flies also dampens in constant darkness.

中文翻译:

Drosophila ezoanauses 一个沙漏或高阻尼生物钟,用于测量夜间长度和诱导滞育

栖息在温带的昆虫测量昼夜长度的季节性变化,以进入越冬滞育期。滞育诱导发生在夜间持续时间超过临界夜间长度 (CNL) 后。在 Bünning 提出昼夜节律系统在光周期时间测量中扮演时钟角色之后,我们对时间测量机制的理解不断发展(Bünning,1936)。最初,光周期时钟被认为要么基于昼夜节律振荡器,要么基于简单的沙漏,这取决于 Nanda-Hamner 和 Bünsow 实验中的“正面”或“负面”反应(Nanda & Hammer,1958 年;Bünsow,1960 年)。然而,也有一些物种的反应既不能被视为“积极”,也不能被视为“消极”,例如北方果蝇物种 Drosophila ezoana,本研究对此进行了调查。此外,建模工作表明,“积极”和“消极”的 Nanda-Hamner 反应也可以由受到不同程度阻尼的昼夜节律振荡器引起:具有高度持续的生物钟的动物将响应“积极”,而昼夜节律严重阻尼的动物时钟将响应“否定”。在本研究中,提出了一种实验测定法,通过确定非 24 小时光/暗周期(T 周期)对临界夜间长度的影响来表征光周期振荡器。据预测,在基于持续振荡器的时钟中,作为 T 循环周期函数的临界夜间长度会发生变化,以及 (ii) 固定的夜间长度测量(即临界夜间长度没有变化)在基于阻尼振荡器的时钟中。果蝇的临界夜间长度约为 7 小时,而与 T 周期无关,这表明基于阻尼振荡器的光周期时钟。活动记录证实了该结论,表明 D. ezoana 苍蝇的活动节律在持续黑暗中也会减弱。
更新日期:2016-09-08
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