Behavioural Neurogenetics Laboratory, Evolutionary and Organismal Biology Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India.
J Biol Rhythms. 2012 Oct;27(5):365-76. doi: 10.1177/0748730412458661.
The fruit fly Drosophila melanogaster has long served as a model system for circadian rhythm research. Various aspects of its genetic, molecular, and circuit-level properties are the subject of investigation, based on which several circadian behaviors and their neuronal controls have been unraveled. In an attempt to address the question of functional significance of circadian organization using a comparative approach, we studied activity/rest rhythm of wild-caught D. melanogaster (DM) and its close relative, Drosophila ananassae (DA). We compared features of the rhythm such as the ability to anticipate morning and evening transitions, presence or absence of morning-associated or evening-associated activity peaks, and phase of these peaks in both species. We found that these 2 sympatric species are different from each other in several aspects of activity/rest rhythm. Unlike DM, which showed a distinct bimodal activity pattern with both morning and evening peaks and a midday interval of relative inactivity under a 12:12-h light/dark regime, DA exhibited unimodal activity with a predominant morning peak, restricting most of its activity to the light phase with no apparent "siesta" during midday. While daytime sleep levels were not different between the 2 species, DA exhibited significantly lesser nighttime activity and higher, more consolidated sleep. This predominant morning activity of DA was also reflected in persistence and phasing of the morning peak under a range of photoperiods. Both under long and short days, the morning peak was the most dominant and persistent peak of DA, whereas the evening peak was more dominant in DM. In addition, DA had a significantly faster circadian clock and more consolidated activity compared with DM. Hence, we hypothesize that these recently diverged sympatric species of fruit flies occupy distinct temporal niches due to differences in their underlying circadian clocks and speculate that they occupy different spatial microenvironments in the wild.
黑腹果蝇（Drosophila melanogaster）长期以来一直是生物钟研究的模式生物系统。其遗传、分子和电路水平特性的各个方面都是研究的主题，在此基础上，已经揭示了几种生物钟行为及其神经元控制。为了尝试使用比较方法解决生物钟组织的功能意义问题，我们研究了野生捕获的黑腹果蝇（DM）及其近缘种，拟暗果蝇（DA）的活动/休息节律。我们比较了两种物种的节律特征，例如预测早晨和傍晚转换的能力、是否存在早晨或傍晚相关的活动高峰以及这些高峰的相位。我们发现，这两个同域物种在活动/休息节律的几个方面存在差异。与表现出明显双峰活动模式（具有早晨和傍晚高峰，以及 12:12 小时光/暗周期中中午相对不活动的间隔）的 DM 不同，DA 表现出单峰活动模式，以主要的早晨高峰为特征，将其大部分活动限制在光相中，中午没有明显的“午休”。虽然两种物种的日间睡眠时间没有差异，但 DA 的夜间活动明显减少，睡眠更为集中。DA 的这种主要早晨活动也反映在一系列光周期下早晨高峰的持久性和相位上。无论是长日还是短日，早晨高峰都是 DA 最主要和持久的高峰，而 DM 则以傍晚高峰为主。此外，与 DM 相比，DA 的生物钟更快，活动更集中。因此，我们假设这些最近分化的同域果蝇物种由于其潜在生物钟的差异而占据不同的时间生态位，并推测它们在野外占据不同的空间微环境。
