Department of Zoology and Entomology, University of Pretoria , Pretoria, South Africa.
Mammal Research Institute, University of Pretoria , Pretoria, South Africa.
Chronobiol Int. 2020 Jun;37(6):824-835. doi: 10.1080/07420528.2020.1782931. Epub 2020 Jul 7.
Diurnality in rodents is relatively rare and occurs primarily in areas with low nighttime temperatures such as at high altitudes and desert areas. However, many factors can influence temporal activity rhythms of animals, both in the field and the laboratory. The temporal activity patterns of the diurnal ice rat were investigated in the laboratory with, and without, access to running wheels, and in constant conditions with running wheels. Ice rats appeared to be fundamentally diurnal but used their running wheels during the night. In constant conditions, general activity remained predominantly diurnal while wheel running was either nocturnal or diurnal. In some animals, entrainment of the wheel running rhythm was evident, as demonstrated by free-running periods that were different from 24 h. In other animals, the wheel running activity abruptly switched from nocturnal to subjective day as soon as the animals entered DD, and reverted back to nocturnal once returned to LD, suggesting the rhythms were masked by light. Wheel running rhythms appears to be less robust and more affected by light compared to general activity rhythms. In view of present and future environmental changes, the existence of more unstable activity rhythms that can readily switch between temporal niches might be crucial for the survival of the species.
昼夜节律在啮齿动物中相对较少见，主要发生在夜间温度较低的地区，如高海拔地区和沙漠地区。然而，许多因素会影响动物在野外和实验室中的时间活动节律。在实验室中，我们研究了昼行冰鼠在有和没有跑步轮以及在有跑步轮的恒常条件下的时间活动模式。冰鼠似乎是基本的昼行性动物，但会在夜间使用它们的跑步轮。在恒常条件下，一般活动主要是昼行性的，而跑步轮活动则是夜间或昼行性的。在一些动物中，跑步轮活动节律的同步现象很明显，表现为自由运行周期与 24 小时不同。在其他动物中，一旦动物进入持续黑暗（DD），跑步轮活动就会突然从夜间切换到主观白天，一旦返回光照-黑暗循环（LD），又会恢复到夜间，这表明节律被光掩盖了。与一般活动节律相比，跑步轮活动节律似乎不那么稳定，更容易受到光照的影响。鉴于当前和未来的环境变化，存在更多不稳定的活动节律，这些节律可以在时间小生境之间快速切换，这可能对物种的生存至关重要。
