An experimental and theoretical analysis of photoperiodic induction in the flesh-Fly,Sarcophaga argyrostoma
An experimental and theoretical analysis of photoperiodic induction in the flesh-Fly,Sarcophaga argyrostoma
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肉蝇石蝇光周期诱导的实验与理论分析
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发表时间：
1978
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通讯作者：
David S. Saunders
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作者：
David S. Saunders
摘要 1.在光周期诱导的实验和正式分析中，石蝇蛹羽化的昼夜节律被用作隐蔽光周期振荡相位的“测量”，特别是在多振荡器昼夜节律系统内的夹带和相位相干性方面。2.羽化起搏器的相位响应曲线是在一系列脉冲长度（1至20）的单脉冲重置实验中获得的。 h）。还根据 Winfree (1970) 心律失常或 R 值对这些数据进行羽化峰的“相干性”分析。 3. 1 小时和 3 小时白光脉冲 (240 μW cm−2) 产生“弱”或 1 型重置曲线，而 5 小时或更长的脉冲产生“强”或 0 型曲线。从LL到DD转换后接近4小时的点开始持续时间接近4小时的脉冲产生高度心律失常的羽化模式，表明脉冲持续时间和相位的这种组合使系统进入其“奇点”。4.在LL/DD转换和重置脉冲开始之间的黑暗小时数（D小时）和脉冲持续时间（L小时）加起来达到一个值的培养物中也观察到心律失常。 (D+L) 接近 12、36、60、84 或 108 小时（模 τ+1/2τ）。然而，当 D+L 加起来接近 24、48、72、96 或 120 小时（模 τ）的值时，获得高度节律的培养物。5. 在幼虫生命的前 5 天跟踪单个 12 小时白光脉冲的相位响应曲线。在从 LL 过渡到 DD 后的前两个周期中，这些脉冲产生了强（0 型）曲线；在随后的周期中，这些曲线从 0 型“衰减”到 1 型。这种变化被认为与发育变化有关，可能与光感受器或其与“时钟”的耦合有关，或者仅仅是行为的变化。 6.从相位响应曲线获得的数据用于计算机程序中，以计算各种“完整”和“骨架”光周期的稳态夹带。这些计算数据还与暴露于相同条件下的培养物的实验确定数据以及从早期实验中获得的滞育诱导数据进行了比较。7.在“完整”光周期（T = 24小时）中，羽化中值（φr）在包含少于14小时光的周期中显示出相位超前黎明，但在较长光周期中相位滞后黎明。 φr 穿过“黎明阈值”的点与滞育诱导的临界光周期值密切匹配。在对称“骨架”（T= 24 h）和不对称“骨架”（T=24 和 72 h）中，计算出的 φr 相位、观测到的 φr 相位和滞育诱导数据都非常一致。 8. 结果根据 Pittendriigh（1966）的光周期时钟“外部符合”模型进行解释，该模型似乎为该物种的光周期诱导提供了最合理的解释。然而，对该模型进行了修改，以纳入多振荡器昼夜节律系统内的内部组织或无组织程度。特别是，这解释了超短日照时滞育发生率的下降，以及“共振”实验的结果。9.S采用的“外部巧合”模型。 argyrostoma 与其他昆虫物种的光周期时钟的形式特性进行了比较，这些特性已得到充分研究。特别是，S之间有很强的相似性。 argyrostoma 和蚜虫 Megoura viciae (Lees, 1973) 都受到胁迫。
Summary1.The circadian rhythm of pupal eclosion inSarcophaga argyrostoma was used as a “measure” of the phase of the covert photoperiodic oscillation in an experimental and formal analysis of photoperiodic induction, particularly in terms of entrainment and phase coherence within the multioscillator circadian system.2.Phase response curves for the eclosion pacemaker were obtained in single pulse resetting experiments for a series of pulse-lengths (1 to 20 h). These data were also analysed for “coherence” of the eclosion peaks in terms of Winfree's (1970) arrhythmicity or R-values.3.One and 3 h pulses of white light (240 μW cm−2) gave rise to “weak” or Type 1 resetting curves, whereas pulses of 5 h or more gave rise to “strong” or Type 0 curves. Pulses close to 4 h in duration starting at points close to 4 h after the transition fromLL to DD gave rise to highly arrhythmic eclosion patterns, suggesting that this combination of pulse duration and phase moved the system on to its “singularity.”4.Arrhythmicity was also observed in cultures in which the number of hours of darkness between theLL/DD transition and the beginning of the resetting pulse (D hours), and the duration of the pulse (L hours) added up to a value (D+L) close to 12, 36, 60, 84 or 108 h (modulo τ+1/2τ). Highly rhythmic cultures, however, were obtained when D+L added up to values close to 24, 48, 72, 96 or 120 h (modulo τ).5.The phase response curves for single 12 h pulses of white light were followed through the first 5 days of larval life. In the first two cycles following the transition fromLL to DD these pulses gave rise to strong (Type 0) curves; in subsequent cycles these curves “decayed” from Type 0 to Type 1. This change is thought to be associated with a developmental change, perhaps in the photoreceptor or its coupling to the “clock” or merely to a change in behaviour.6.The data obtained from phase response curves were used in a computer program to calculate steady-state entrainment to a variety of “complete” and “skeleton” photoperiods. These computed data were also compared with those experimentally determined for cultures exposed to identical regimes, and to diapause induction data obtained from earlier experiments.7.In “complete” photoperiods (T=24 h) the median of eclosion (φr) was shown to phase-lead dawn in cycles containing less than 14 h of light, but to phase-lag dawn in longer photoperiods. The point at whichφr crossed the “dawn threshold” closely matched the value of the critical photoperiod for diapause induction. In symmetrical “skeletons” (T= 24 h) and asymmetrical “skeletons” (T=24 and 72 h) computed phases ofφr, observed phases ofφr, and diapause induction data were all in close agreement.8.The results are interpreted in terms of Pittendrigh's (1966) “external coincidence” model for the photoperiodic clock, the model which appears to offer the most plausible explanation for photoperiodic induction in this species. The model is modified, however, to incorporate the degree of internal organisation or disorganisation within the multioscillator circadian system. In particular, this accounts for the fall in diapause incidence in ultra-short daylengths, and for the results of “resonance” experiments.9.The “external coincidence” model, as adopted forS. argyrostoma, is compared with the formal properties of the photoperiodic clock in other insect species which have been adequately investigated. In particular, the strong similarities betweenS. argyrostoma and the aphid,Megoura viciae (Lees, 1973), are stressed.