Data from: Male sperm storage compromises sperm motility in guppies.

Sperm senescence can have important evolutionary implications due to its deleterious effects on sperm quality and offspring performance. Consequently, it has been argued that polyandry (female multiple mating) may facilitate the selection of younger, and therefore competitively superior, sperm when ejaculates from multiple males compete for fertilisation. Surprisingly, however, unequivocal evidence that sperm ageing influences traits that underlie sperm competitiveness is lacking. Here, we used a paired experimental design that compares sperm quality between experimentally ‘old’ and ‘young’ ejaculates from individual male guppies (Poecilia reticulata). We show that older sperm exhibit significant reductions in sperm velocity compared to younger sperm from the same males. We found no evidence that the brightness of the male’s orange (carotenoid) spots, which are thought to signal resistance to oxidative stress (and thus age-related declines in sperm fitness), signals a male’s ability to withstand the deleterious effects of sperm ageing. Instead, polyandry may be a more effective strategy for females to minimise the likelihood of being fertilised by aged sperm.精子衰老因其对精子质量与后代表现的有害影响，而具备重要的进化生物学意义。据此有研究提出，当多只雄性的精子竞争受精机会时，一妻多夫制（polyandry，即雌性多次交配）或可推动选择更年轻、因而竞争能力更强的精子。然而令人意外的是，目前仍缺乏确凿证据表明，精子衰老会影响支撑精子竞争能力的相关性状。本研究采用配对实验设计，对比了实验诱导的“衰老”与“年轻”精子在同一雄性孔雀鱼（Poecilia reticulata）个体中的质量差异。研究结果显示，相较于同雄性个体的年轻精子，衰老精子的游动速度显著降低。我们未发现证据表明，雄性的橙色（类胡萝卜素）色斑——这类色斑被认为可反映其抗氧化应激能力（进而反映精子健康随衰老发生的衰退情况）——能够体现雄性抵御精子衰老有害影响的能力。相较而言，一妻多夫制或为雌性降低被衰老精子受精概率的更有效策略。