Reierth E, Stokkan K A
Department of Arctic Biology, University of Tromsø, Norway.
J Biol Rhythms. 1998 Oct;13(5):393-402. doi: 10.1177/074873049801300504.
The possibility that feeding may act as a zeitgeber has been investigated in captive Svalbard ptarmigan by recording feeding or food-searching activity (FA) in birds given periodic access to food (PAF) under light-dark (LD) cycles or in continuous bright (LL) or dim light (DD) conditions. Except during LL, anticipatory attempts to feed always occurred prior to the food access interval with a relatively stable phase relationship to the interval. There was always a second bout of feeding toward the end of the food access interval, which apparently corresponds to the afternoon bout of feeding, seen under LD and ad libitum access to food. During PAF, this afternoon peak of activity disappeared. When the LD cycle was phase delayed while restricted access to food remained unchanged, the afternoon peak of feeding was temporarily reestablished but was transiently shifted forward to reattain its position within the food access interval. After termination of PAF, the afternoon bout of feeding was reestablished through phase-delaying transients, with an initial phase corresponding to the previous food access interval. The results suggest that FA of Svalbard ptarmigan is controlled by 2 separate circadian oscillators, both of which can be entrained by light and food: a putative morning oscillator, which controls the activity associated with the beginning of the photoperiod or the food access interval, and a putative evening oscillator, which induces increased activity toward the end of these intervals. In their natural environment at very high latitudes, Svalbard ptarmigan deposit fat when the day length declines rapidly in autumn. Entrained by feeding, they appear to enjoy a longer daily period of food-searching activity than if day length was the only zeitgeber.
通过记录圈养的斯瓦尔巴德岩雷鸟在明暗（LD）周期下或持续明亮（LL）或昏暗光照（DD）条件下定期获取食物（PAF）时的进食或觅食活动（FA），研究了进食可能作为一个授时因子的可能性。除了在LL条件下，预期的进食尝试总是在食物获取间隔之前发生，并且与该间隔具有相对稳定的相位关系。在食物获取间隔接近尾声时总是会出现第二轮进食，这显然对应于在LD和自由获取食物条件下看到的下午进食时段。在PAF期间，这个下午的活动高峰消失了。当LD周期相位延迟而食物获取受限保持不变时，下午的进食高峰会暂时重新建立，但会短暂地向前移动以重新回到其在食物获取间隔内的位置。在PAF终止后，下午的进食时段通过相位延迟瞬变重新建立，初始相位对应于之前的食物获取间隔。结果表明，斯瓦尔巴德岩雷鸟的FA由2个独立的昼夜节律振荡器控制，这两个振荡器都可以被光和食物同步：一个假定的早晨振荡器，它控制与光周期开始或食物获取间隔开始相关的活动；一个假定的傍晚振荡器，它在这些间隔接近尾声时诱导活动增加。在极北地区的自然环境中，当秋季白昼长度迅速缩短时，斯瓦尔巴德岩雷鸟会储存脂肪。受进食同步，它们似乎比仅以白昼长度作为唯一授时因子时享有更长的每日觅食活动时间。
