Males of many species evolved the capability of adjusting their ejaculate phenotype in response to social cues to match the expected mating conditions. When females store sperm for a prolonged time, the expected fitness return of plastic adjustments of ejaculate phenotype may depend on the interval between mating and fertilization. Although prolonged female sperm storage (FSS) increases the opportunity for sperm competition, as a consequence of the longer temporal overlap of ejaculates from several males, it may also create variable selective forces on ejaculate phenotype, for example by exposing trade‐offs between sperm velocity and sperm survival. We evaluated the relationship between the plasticity of ejaculate quality and FSS in the guppy, Poecilia reticulata, a polyandrous live‐bearing fish in which females store sperm for several months and where stored sperm contribute significantly to a male's lifelong reproductive success. In this species, males respond to the perception of future mating opportunities by increasing the quantity (number) and quality (swimming velocity) of ready‐to‐use sperm (an anticipatory response called ‘sperm priming’). Here we investigated (a) the effect of sperm priming on in vitro sperm viability at stripping and its temporal decline (as an estimate of sperm survival), and (b) the in vivo competitive fertilization success in relation to female sperm storage using artificial insemination. As expected, sperm‐primed males produced more numerous and faster sperm, but with a reduced in vitro sperm viability at stripping and after 4 hr, compared with their counterparts. Artificial insemination revealed that the small (nonsignificant) advantage of primed sperm when fertilization immediately follows insemination is reversed when eggs are fertilized by female‐stored sperm, weeks after insemination. By suggesting a plastic trade‐off between sperm velocity and viability, these results demonstrate that prolonged female sperm storage generates divergent selection pressures on ejaculate phenotype.

中文翻译：

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雌性精子储存介导了孔雀鱼射精预期可塑性的交配后成本和收益

许多物种的雄性进化出调整射精表型的能力，以响应社会线索以匹配预期的交配条件。当雌性长时间储存​​精子时，射精表型的塑料调整的预期健康恢复可能取决于交配和受精之间的间隔。尽管延长的女性精子储存 (FSS) 增加了精子竞争的机会，但由于几个男性射精的时间重叠时间较长，它也可能对射精表型产生可变的选择力，例如通过暴露精子速度之间的权衡和精子存活。我们评估了孔雀鱼的射精质量可塑性与 FSS 之间的关系，Poecilia reticulata，一种一妻多夫的活产鱼，雌性将精子储存数月，其中储存的精子对雄性的终生繁殖成功有重大贡献。在这个物种中，雄性通过增加即用型精子的数量（数量）和质量（游泳速度）（一种称为“精子启动”的预期反应）来对未来交配机会的感知做出反应。在这里，我们研究了（a）精子启动对剥离时体外精子活力的影响及其时间下降（作为精子存活的估计），以及（b）与使用人工授精的女性精子储存相关的体内竞争性受精成功. 正如预期的那样，精子引发的雄性产生更多和更快的精子，但在剥离时和 4 小时后，与它们的对应物相比，体外精子活力降低。人工授精表明，当受精后数周内，雌性储存的精子使卵子受精时，在受精后立即受精时，受精精子的小（不显着）优势被逆转。通过暗示精子速度和活力之间的可塑性权衡，这些结果表明女性精子储存时间延长会对射精表型产生不同的选择压力。