Centre for Evolutionary Biology, School of Biological Sciences, University of Western Australia, Crawley, WA, Australia.
Proc Biol Sci. 2023 May 31;290(1999):20230574. doi: 10.1098/rspb.2023.0574. Epub 2023 May 24.
Female reproductive fluids (FRFs) serve key reproductive functions in sexually reproducing animals, including modifying the way sperm swim and detect eggs, and influencing sperm lifespan. Despite the central role of FRF during fertilization, we know surprisingly little about sperm-FRF interactions under different environmental conditions. Theory suggests that in external fertilizers FRF may 'rescue' sperm from ageing effects as they search to fertilize eggs. Here, we test the interaction between these two fundamental properties of the fertilization environment, ejaculate age (i.e. time since ejaculation) and FRF, on a range of functional sperm phenotypes in a broadcast spawning mussel, . We found that the effects of ejaculate age on multivariate sperm motility traits and total sperm motility were altered by FRF, and that longer-lived sperm exhibit stronger, likely more advantageous, responses to FRF after periods of ageing. We also detected significant among-male variation in the relationship between sperm motility traits and ejaculate age; notably, these patterns were only revealed when sperm encountered FRF. Collectively these findings underscore the importance of considering female reproductive physiology when interpreting ageing-related declines in sperm motility, as doing so may expose importance sources of variation in sperm phenotypic plasticity among males and environments.
雌性生殖液（Female reproductive fluids，FRFs）在有性生殖动物中发挥着关键的生殖功能，包括改变精子游动和识别卵子的方式，以及影响精子寿命。尽管 FRF 在受精过程中起着核心作用，但我们对不同环境条件下精子-FRF 相互作用的了解却少得惊人。理论表明，在外部受精中，当精子寻找卵子受精时，FRF 可能会“挽救”精子免受衰老的影响。在这里，我们在一种广播式产卵贻贝中测试了受精环境的这两个基本特性——精液年龄（即射精后的时间）和 FRF 之间的相互作用，研究了一系列功能精子表型。我们发现，FRF 改变了精液年龄对多变量精子运动特征和总精子运动的影响，并且寿命较长的精子在衰老后对 FRF 的反应更强，可能更有利。我们还检测到了精子运动特征与精液年龄之间的关系存在显著的雄性间变异性；值得注意的是，只有当精子遇到 FRF 时，才会出现这些模式。这些发现共同强调了在解释与衰老相关的精子运动能力下降时考虑雌性生殖生理学的重要性，因为这样做可能会揭示雄性和环境之间精子表型可塑性的重要变异来源。
