Laboratório de Cronobiologia, Departamento de Fisiologia, Universidade Federal do Rio Grande do Norte, Natal, Rio Grande do Norte, Brazil.
Chronobiol Int. 2013 Jul;30(6):818-27. doi: 10.3109/07420528.2013.767823. Epub 2013 Jun 14.
Synchronized state of activity and rest might be attained by mechanisms of entrainment and masking. Most zeitgebers not only act to entrain but also to mask circadian rhythms. Although the light-dark (LD) cycle is the main zeitgeber of circadian rhythms in marmosets, social cues can act as weaker zeitgebers. Evidence on the effects of social entrainment in marmosets has been collected in isolated animals or in pairs where activity is not individually recorded. To characterize the synchronization between the daily activity profiles of individuals in groups under LD conditions, the motor activity of animals from five groups was continuously monitored using actiwatches for 15 days during the 5th, 8th, and 11th months of life of juveniles. Families consisting of twins (4 ♂♀/1 ♂♂) and their parents were maintained under controlled lighting (LD 12:12 h), temperature, and humidity conditions. Synchronization was evaluated through the synchrony between the circadian activity profiles obtained from the Pearson correlation index between possible pairs of activity profiles in the light and dark phases. We also calculated the phase-angle differences between the activity onset of one animal in relation to the activity onset of each animal in the group (ψ(on)). A similar procedure was performed for activity offset (ψ(off)). By visual analysis, the correlation between the activity profiles of individuals within each family was stronger than that of individuals from different families. A mixed-model analysis showed that within the group, the correlation was stronger between twins than between twins and their parents in all families, except for the family in which both juveniles were males. Because a twin is an important social partner for juveniles, a sibling is likely to have a stronger influence on its twin's activity rhythm than other family members. Considering only the light phase, the second strongest correlation was observed between the activity profiles of the individuals in the reproductive pair. Regarding the parameters ψ(on) and ψ(off), the juvenile/juvenile dyad had lower values than the other dyads, but these differences did not reach statistical significance in relation to all dyads. Comparing the results of the ψ(on) and ψ(off), and correlation indices, we suggest that the latter could detect differences between the animals that were not observed in the results of the phase-angle differences. These differences could be related to changes that occur during the active phase but not only in a particular phase, such as the temporal changes during the activity phase that characterize unimodal or bimodal patterns. Based on the differences in the correlations between individuals subjected to the same LD routine, we suggest that social cues modulate the circadian activity profiles of marmosets as a result of interactions between the animals within each group. Future studies are necessary to characterize the mechanisms of synchronization that are involved in this social modulation.
活动和休息的同步状态可能通过同步和掩蔽机制来实现。大多数授时因子不仅起同步作用，还起掩蔽作用。虽然光-暗（LD）周期是狨猴昼夜节律的主要授时因子，但社会线索可以作为较弱的授时因子。关于狨猴社会同步的证据是在孤立的动物或在没有单独记录活动的成对动物中收集的。为了描述在 LD 条件下群体中个体的日常活动谱之间的同步性，使用 actiwatches 在 5、8 和 11 个月大的幼崽生命期间连续监测来自五个群体的动物的运动活动 15 天。由双胞胎（4♀♂/1♂♂）及其父母组成的家庭在受控光照（LD 12:12 h）、温度和湿度条件下维持。通过皮尔逊相关指数在光暗相期间可能的活动谱对之间获得的昼夜活动谱之间的同步性来评估同步性。我们还计算了一个动物的活动起始相对于组内每个动物的活动起始之间的相位角差异（ψ（on））。对于活动结束（ψ（off）），执行了类似的程序。通过视觉分析，每个家庭内个体的活动谱之间的相关性强于不同家庭个体的相关性。混合模型分析表明，在组内，双胞胎之间的相关性强于所有家庭中双胞胎与其父母之间的相关性，除了两个幼崽都是雄性的家庭。因为双胞胎是幼崽的重要社会伴侣，所以兄弟姐妹对其双胞胎的活动节律的影响可能比其他家庭成员更强。仅考虑光相，在生殖对的个体之间的活动谱之间观察到第二强的相关性。关于参数 ψ（on）和 ψ（off），幼崽/幼崽二联体的值低于其他二联体的值，但与所有二联体相比，这些差异没有达到统计学意义。比较 ψ（on）和 ψ（off）以及相关指数的结果，我们建议后者可以检测到在相位角差异结果中未观察到的动物之间的差异。这些差异可能与活动期间发生的变化有关，而不仅仅是在特定阶段，例如在活动阶段期间表征单峰或双峰模式的时间变化。基于受相同 LD 常规影响的个体之间的相关性差异，我们认为社会线索通过每个组内动物之间的相互作用来调节狨猴的昼夜活动谱。有必要进行未来的研究来描述参与这种社会调节的同步机制。
