Strategic ejaculate adjustments occur when males modify their investment in sperm and nonsperm components of the ejaculate according to the context. This strategy is expected to evolve when ejaculate production is costly, the returns of the investment in the ejaculate depend on the environment and environmental conditions are variable. While adjustments of sperm numbers have been widely documented, only recently we have begun to investigate how males modify ejaculate quality, despite the recognized importance of this factor for sperm competition. Here I discuss and synthetize existing literature on strategic adjustments of ejaculate quality. I describe which ejaculate quality traits are most typically plastic and which environmental factors elicit such responses, focusing especially on the socio-sexual environment. I summarize information on the timeframe within which adjustments can occur and on the proximate mechanisms responsible for plasticity. I show that this phenomenon is widespread across taxa; it involves responses to several environmental factors and modifications of many ejaculate traits, with seminal fluid composition playing a central role, as a trait per se and as proximate mechanism for sperm performance adjustments. I point out the circumstances favoring the evolution of ejaculate quality plasticity, and evaluate the fitness consequences of these responses, highlighting the complexity of patterns of covariation with other traits. Finally, I consider implications for male and female behavior. I highlight two areas of research on ejaculate plasticity that may be particularly worth exploring further: 1) the proximate mechanisms responsible for plasticity; 2) the adaptive value of strategic ejaculate adjustments.

当男性根据情况改变对射精的精子和非精子成分的投资时，就会进行战略性射精调整。当射精的生产成本高昂，射精投资的回报取决于环境且环境条件可变时，预计该策略将会发展。尽管已广泛记录了精子数量的调节，但直到最近，我们才开始研究雄性如何改变射精质量，尽管该因素对精子竞争至关重要。在这里，我讨论并综合了有关射精质量战略调整的现有文献。我描述了哪些射精品质特征最典型地是可塑的，哪些环境因素引起了这种反应，尤其着重于社会性别环境。我总结了可能进行调整的时间范围以及负责可塑性的邻近机制的信息。我表明这种现象在整个分类群中都很普遍。它涉及对几种环境因素的反应和许多射精性状的改变，其中精液成分起着核心作用。本身，并作为精子性能调节的最接近机制。我指出了有利于射精质量可塑性发展的情况，并评估了这些反应的适应性后果，突出了与其他特征的协变模式的复杂性。最后，我考虑了对男性和女性行为的影响。我重点介绍射精可塑性的两个研究领域，这些领域可能特别值得进一步探讨：1）引起可塑性的主要机制； 2。2）战略射精调整的适应性价值。