Mildner Stephanie, Roces Flavio
Department of Behavioral Biology and Sociobiology (Zoology II), Biocenter, University of Würzburg, Würzburg, Germany.
PLoS One. 2017 Jan 18;12(1):e0169244. doi: 10.1371/journal.pone.0169244. eCollection 2017.
Daily activities within an ant colony need precise temporal organization, and an endogenous clock appears to be essential for such timing processes. A clock drives locomotor rhythms in isolated workers in a number of ant species, but its involvement in activities displayed in the social context is unknown. We compared locomotor rhythms in isolated individuals and behavioral rhythms in the social context of workers of the ant Camponotus rufipes. Both forager and nurse workers exhibited circadian rhythms in locomotor activity under constant conditions, indicating the involvement of an endogenous clock. Activity was mostly nocturnal and synchronized with the 12:12h light-dark-cycle. To evaluate whether rhythmicity was maintained in the social context and could be synchronized with non-photic zeitgebers such as feeding times, daily behavioral activities of single workers inside and outside the nest were quantified continuously over 24 hours in 1656 hours of video recordings. Food availability was limited to a short time window either at day or at night, thus mimicking natural conditions of temporally restricted food access. Most foragers showed circadian foraging behavior synchronized with food availability, either at day or nighttime. When isolated thereafter in single locomotor activity monitors, foragers mainly displayed arrhythmicity. Here, high mortality suggested potential stressful effects of the former restriction of food availability. In contrast, nurse workers showed high overall activity levels in the social context and performed their tasks all around the clock with no circadian pattern, likely to meet the needs of the brood. In isolation, the same individuals exhibited in turn strong rhythmic activity and nocturnality. Thus, endogenous activity rhythms were inhibited in the social context, and timing of daily behaviors was flexibly adapted to cope with task demands. As a similar socially-mediated plasticity in circadian rhythms was already shown in honey bees, the temporal organization in C. rufipes and honey bees appear to share similar basic features.
蚁群中的日常活动需要精确的时间组织，而内源性时钟似乎对于此类计时过程至关重要。在许多蚂蚁物种中，时钟驱动着隔离状态下工蚁的运动节律，但其在社会环境中所表现出的活动中的作用尚不清楚。我们比较了红足弓背蚁工蚁在隔离状态下的运动节律和社会环境中的行为节律。觅食工蚁和保育工蚁在恒定条件下的运动活动均表现出昼夜节律，这表明内源性时钟参与其中。活动大多在夜间进行，并与12:12小时的明暗周期同步。为了评估节律性在社会环境中是否得以维持，以及是否能与诸如喂食时间等非光性 Zeitgeber 同步，我们在1656小时的视频记录中，对单个工蚁在巢内和巢外24小时的日常行为活动进行了连续量化。食物供应被限制在白天或晚上的一个短时间窗口内，从而模拟了食物获取在时间上受限的自然条件。大多数觅食工蚁表现出与食物供应同步的昼夜觅食行为，无论是在白天还是夜间。此后，当将觅食工蚁隔离在单个运动活动监测器中时，它们主要表现出无节律性。在此，高死亡率表明先前食物供应受限可能产生应激效应。相比之下，保育工蚁在社会环境中表现出较高的总体活动水平，全天候执行任务且无昼夜模式，这可能是为了满足幼虫的需求。在隔离状态下，同样的个体依次表现出强烈的节律性活动和夜行性。因此，内源性活动节律在社会环境中受到抑制，日常行为的时间安排被灵活调整以应对任务需求。由于在蜜蜂中已经显示出类似的社会介导的昼夜节律可塑性，红足弓背蚁和蜜蜂的时间组织似乎具有相似的基本特征。
