Karagicheva Julia, Rakhimberdiev Eldar, Dekinga Anne, Brugge Maarten, Koolhaas Anita, Ten Horn Job, Piersma Theunis
NIOZ Royal Netherlands Institute for Sea Research, Department of Coastal Systems and Utrecht University, Den Burg, Texel, the Netherlands
NIOZ Royal Netherlands Institute for Sea Research, Department of Coastal Systems and Utrecht University, Den Burg, Texel, the Netherlands Department of Vertebrate Zoology, Biological Faculty, Lomonosov Moscow State University, Moscow, Russia.
J Biol Rhythms. 2016 Oct;31(5):509-21. doi: 10.1177/0748730416655929. Epub 2016 Jul 27.
Because of the complications in achieving the necessary long-term observations and experiments, the nature and adaptive value of seasonal time-keeping mechanisms in long-lived organisms remain understudied. Here we present the results of a 20-year-long study of the repeated seasonal changes in body mass, plumage state, and primary molt of 45 captive red knots Calidris canutus islandica, a High Arctic breeding shorebird that spends the nonbreeding season in temperate coastal areas. Birds kept outdoors and experiencing the natural photoperiod of the nonbreeding area maintained sequences of life-cycle stages, roughly following the timing in nature. For 6 to 8 years, 14 of these birds were exposed to unvarying ambient temperature (12 °C) and photoperiodic conditions (12:12 LD). Under these conditions, for at least 5 years they expressed free-running circannual cycles of body mass, plumage state, and wing molt. The circannual cycles of the free-running traits gradually became longer than 12 months, but at different rates. The prebreeding events (onset and offset of prealternate molt and the onset of spring body mass increase) occurred at the same time of the year as in the wild population for 1 or several cycles. As a result, after 4 years in 12:12 LD, the circannual cycles of prealternate plumage state had drifted less than the cycles of prebasic plumage state and wing molt. As the onset of body mass gain drifted less than the offset, the period of high body mass became longer under unvarying conditions. We see these differences between the prebreeding and postbreeding life-cycle stages as evidence for adaptive seasonal time keeping in red knots: the life-cycle stages linked to the initiation of reproduction rely mostly on endogenous oscillators, whereas the later stages rather respond to environmental conditions. Postbreeding stages are also prone to carryover effects from the earlier stages.
由于在进行必要的长期观测和实验时存在诸多复杂因素，长寿生物体中季节性计时机制的本质和适应性价值仍未得到充分研究。在此，我们展示了一项为期20年的研究结果，该研究针对45只圈养的红腹滨鹬（Calidris canutus islandica）的体重、羽毛状态和初级换羽的反复季节性变化展开，红腹滨鹬是一种在北极地区高纬度繁殖的滨鸟，非繁殖季节栖息于温带沿海地区。饲养在户外并经历非繁殖区自然光照周期的鸟类维持着生命周期各阶段的顺序，大致遵循自然中的时间安排。在6至8年的时间里，其中14只鸟被置于恒定的环境温度（12°C）和光照周期条件（12:12 LD）下。在这些条件下，它们至少在5年的时间里表现出体重、羽毛状态和翅膀换羽的自由运行的年周期循环。自由运行特征的年周期循环逐渐变得长于12个月，但速率不同。繁殖前的事件（前交替换羽的开始和结束以及春季体重增加的开始）在一年中的同一时间发生，与野生种群中的情况相同，持续1个或几个周期。结果，在12:12 LD条件下4年后，前交替羽毛状态的年周期循环漂移程度小于基本羽毛状态和翅膀换羽的循环。由于体重增加的开始漂移程度小于结束，在恒定条件下高体重期变得更长。我们将繁殖前和繁殖后生命周期阶段之间的这些差异视为红腹滨鹬适应性季节性计时的证据：与繁殖开始相关的生命周期阶段主要依赖内源性振荡器，而后期阶段则更多地对环境条件做出反应。繁殖后阶段也容易受到早期阶段的遗留效应影响。
