Data from: Male responses to sperm competition risk associated with increased macronutrient intake and reduced lifespan

Increased expenditure on the ejaculate is a taxonomically widespread male response to sperm competition. Increased ejaculate expenditure is assumed to come at a cost to future reproduction, otherwise males should always invest maximally. However, the life-history costs of strategic ejaculation are not well documented. Macronutrient intake is known to affect the trade-off between reproduction and lifespan. Intakes of protein and carbohydrate that maximise reproduction are often differ from those that maximise lifespan. Here, we asked whether strategic expenditure on the ejaculate by male crickets, Teleogryllus oceanicus, is mediated by macronutrient intake, and whether it comes at a cost of reduced lifespan. Males were exposed to rival song throughout their lifespan or were held in a silent non-competitive environment. Males exposed to song had a higher intake of both protein and carbohydrate, they reached adulthood sooner, produced ejaculates of higher quality, and died sooner than males living in a silent environment. Our findings provide a rare example of both the mechanisms and life-history costs associated with strategic ejaculation.

精液投入量的提升是雄性应对精子竞争的一种跨分类群普遍存在的适应性响应。学界普遍假设，精液投入增加会以未来繁殖为代价，否则雄性本应始终采取最大化投入策略。然而，策略性射精的生活史代价尚未得到充分记录。已知宏量营养素（macronutrient）摄入会影响繁殖与寿命之间的权衡，能够最大化繁殖成效的蛋白质与碳水化合物摄入量，往往与最大化寿命的摄入量存在差异。本研究以澳洲钟蟋（Teleogryllus oceanicus）的雄性个体为对象，探究其策略性精液投入是否受宏量营养素摄入的调控，以及该投入是否会以寿命缩短为代价。实验中将雄性钟蟋分为两组：一组在整个生命周期中持续暴露于竞争对手的鸣唱声中，另一组则处于无竞争的静音环境。相较于静音环境中的个体，暴露于鸣唱声的雄性不仅摄入了更多的蛋白质与碳水化合物，且更早达到性成熟，产出的精液品质更高，但寿命更短。本研究结果为策略性射精相关的调控机制与生活史代价提供了一个罕见的实证案例。