Behavioural Ecology Division, Institute of Ecology and Evolution, University of Bern, Switzerland.
Behavioural Ecology Division, Institute of Ecology and Evolution, University of Bern, Switzerland.
Horm Behav. 2021 Feb;128:104910. doi: 10.1016/j.yhbeh.2020.104910. Epub 2020 Dec 17.
In cooperatively breeding cichlid fish, the early social environment has lifelong effects on the offspring's behaviour, life-history trajectories and brain gene expression. Here, we asked whether the presence or absence of parents and subordinate helpers during early life also shapes fluctuating levels of cortisol, the major stress hormone in the cichlid Neolamprologus pulcher. To non-invasively characterize baseline and stress-induced cortisol levels, we adapted the 'static' holding-water method often used to collect waterborne steroid hormones in aquatic organisms by including a flow-through system allowing for repeated sampling without handling of the experimental subjects. We used 8-year-old N. pulcher either raised with (+F) or without (-F) parents and helpers in early life. We found that N. pulcher have a peak of their circadian cortisol cycle in the early morning, and that they habituated to the experimental procedure after four days. Therefore, we sampled the experimental fish in the afternoon after four days of habituation. -F fish had significantly lower baseline cortisol levels, whereas stress-induced cortisol levels did not differ between treatments. Thus, we show that the early social environment has life-long effects on aspects of the physiological stress system of the Hypothalamic-Pituitary-Interrenal (HPI) axis. We discuss how these differences in physiological state may have contributed to the specialization in different social and life-history trajectories of this species.
在合作繁殖的丽鱼科鱼类中，早期的社会环境对后代的行为、生活史轨迹和大脑基因表达具有终身影响。在这里，我们想知道在早期生活中是否存在亲鱼和从属助手是否也会影响慈鲷 Neolamprologus pulcher 的皮质醇（主要的应激激素）波动水平。为了非侵入性地描述皮质醇的基线和应激诱导水平，我们通过包括允许在不处理实验对象的情况下进行重复采样的流动系统，改编了常用于收集水生生物中水溶性类固醇激素的“静态”持水法。我们使用 8 岁的 N. pulcher，它们要么在早期生活中与亲鱼和助手一起饲养 (+F)，要么没有 (-F)。我们发现 N. pulcher 的皮质醇昼夜节律周期在清晨达到峰值，并且在经过四天的适应后，它们对实验程序产生了习惯。因此，在适应四天后的下午，我们对实验鱼进行了采样。-F 鱼的基线皮质醇水平明显较低，而应激诱导的皮质醇水平在两种处理之间没有差异。因此，我们表明，早期的社会环境对下丘脑-垂体-肾上腺（HPI）轴生理应激系统的各个方面具有终身影响。我们讨论了这些生理状态的差异如何可能促成该物种不同的社会和生活史轨迹的专业化。
