The Challenge Hypothesis (Wingfield et al. Am. Nat. 136, 829-846) aims to explain the complex relationship between androgens and social interactions. Despite its well acceptance in the behavioral endocrinology literature, several studies have failed to found an androgen response to staged social interactions. Possible reasons for these inconsistencies are the use of single sampling points that may miss the response peak, and the occurrence of inter-individual variability in the androgen response to social interactions. In this study we addressed these two possible confounding factors by characterizing the temporal pattern of the androgen response to social interactions in the African cichlid, Oreochromis mossambicus, and relating it to inter-individual variation in terms of the individual scope for androgen response (i.e. the difference between baseline and maximum physiological levels for each fish) and behavioral types. We found that the androgen response to territorial intrusions varies between individuals and is related to their scope for response. Individuals that have a lower scope for androgen response did not increase androgens after a territorial intrusion but were more aggressive and exploratory. In contrast males with a higher scope for response had fewer aggressive and exploratory behaviors and exhibited two peaks of KT, an early response 2-15 min after the interaction and a late response at 60-90 min post-interaction. Given that the pharmacological challenge of the Hypothalamic-Pituitary-Gonad axis only elicits the late response, we suggest that these two peaks may be regulated by different physiological mechanisms, with the early response being mediated by direct brain-gonad neural pathways. In summary, we suggest that determining the temporal pattern of the androgen response to social interactions and considering inter-individual variation may be the key to understanding the contradictory results of the Challenge Hypothesis.

中文翻译：

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迎接挑战？雄激素对慈鲷鱼社会互动反应的个体差异。

The Challenge Hypothesis (Wingfield et al. Am. Nat. 136, 829-846) 旨在解释雄激素与社会互动之间的复杂关系。尽管它在行为内分泌学文献中被广泛接受，但几项研究未能发现雄激素对分阶段社会互动的反应。这些不一致的可能原因是使用可能错过反应峰值的单个采样点，以及雄激素对社会互动的反应发生个体间差异。在这项研究中，我们通过描述非洲慈鲷 Oreochromis mossambicus 对社会互动的雄激素反应的时间模式，并将其与雄激素反应的个体范围（即 每条鱼的基线和最大生理水平之间的差异）和行为类型。我们发现雄激素对领土入侵的反应因人而异，并且与他们的反应范围有关。雄激素反应范围较低的个体在领土入侵后不会增加雄激素，而是更具侵略性和探索性。相比之下，具有较高反应范围的雄性具有较少的攻击性和探索性行为，并表现出两个 KT 峰值，即互动后 2-15 分钟的早期反应和互动后 60-90 分钟的晚期反应。鉴于下丘脑-垂体-性腺轴的药理学挑战仅引起晚期反应，我们认为这两个峰可能受不同生理机制的调节，早期反应是由直接的脑 - 性腺神经通路介导的。总之，我们建议确定雄激素对社会互动反应的时间模式并考虑个体间差异可能是理解挑战假说的矛盾结果的关键。