Simons Mirre J P, Sebire Marion, Verhulst Simon, Groothuis Ton G G
School of Biosciences, University of Sheffield, Sheffield, United Kingdom.
The Centre for Environment, Fisheries and Aquaculture Science, Weymouth, United Kingdom.
Front Cell Dev Biol. 2021 Dec 17;9:752352. doi: 10.3389/fcell.2021.752352. eCollection 2021.
Costs of reproduction shape the life-history evolution of investment in current and future reproduction and thereby aging. Androgens have been proposed to regulate the physiology governing these investments. Furthermore, androgens are hypothesized to play a central role in carotenoid-dependent sexual signaling, regulating how much carotenoids are diverted to ornamentation and away from somatic maintenance, increasing oxidative stress, and accelerating aging. We investigated these relationships in male three-spined stickleback in which we elevated 11-ketotestosterone and supplied vitamin E, an antioxidant, in a 2 × 2 design. Androgen elevation shortened the time stickleback maintained reproductive activities. We suspect that this effect is caused by 11-ketotestosterone stimulating investment in current reproduction, but we detected no evidence for this in our measurements of reproductive effort: nest building, body composition, and breeding coloration. Carotenoid-dependent coloration was even slightly decreased by 11-ketotestosterone elevation and was left unaffected by vitamin E. Red coloration correlated with life expectancy and reproductive capacity in a quadratic manner, suggesting overinvestment of the individuals exhibiting the reddest bellies. In contrast, blue iris color showed a negative relationship with survival, suggesting physiological costs of producing this aspect of nuptial coloration. In conclusion, our results support the hypothesis that androgens regulate investment in current versus future reproduction, yet the precise mechanisms remain elusive. The quadratic relationships between sexual signal expression and aspects of quality have wider consequences for how we view sexual selection on ornamentation and its relationship with aging.
繁殖成本塑造了当前和未来繁殖投资以及衰老过程中的生活史进化。雄激素被认为可调节控制这些投资的生理过程。此外，有假说认为雄激素在依赖类胡萝卜素的性信号传导中起核心作用，调节有多少类胡萝卜素被转移用于装饰而非躯体维持，增加氧化应激，并加速衰老。我们在雄性三刺鱼中研究了这些关系，采用2×2设计，升高11-酮睾酮水平并提供抗氧化剂维生素E。雄激素水平升高缩短了三刺鱼维持繁殖活动的时间。我们怀疑这种效应是由11-酮睾酮刺激当前繁殖投资引起的，但在我们对繁殖努力的测量（筑巢、身体组成和繁殖体色）中未检测到相关证据。11-酮睾酮水平升高甚至使依赖类胡萝卜素的体色略有下降，且维生素E对其无影响。红色体色与预期寿命和繁殖能力呈二次函数关系，表明腹部最红的个体存在过度投资。相比之下，蓝色虹膜颜色与生存呈负相关，表明产生这种婚羽颜色方面存在生理成本。总之，我们的结果支持雄激素调节当前与未来繁殖投资的假说，但具体机制仍不清楚。性信号表达与质量方面的二次函数关系对于我们如何看待装饰性的性选择及其与衰老的关系具有更广泛的影响。
