In many species, males show anticipatory plasticity for sperm production, which they adjust to match perceived mating opportunities. While the strategic adjustment of sperm production is likely to be beneficial, it may be also associated with costs, including those arising from the expression of a phenotype that is poorly matched to the conditions that males will subsequently experience. Mismatch costs are exacerbated by trade-offs between investment in the ejaculate and investment in other traits and by trade-offs among individual ejaculate traits. Trade-offs, in fact, may determine a decrease in male competitiveness, due to impaired ability to obtain copulations or to reduced ejaculate quality. We explored mismatch costs using male guppies, which are known to increase sperm production, but reduce their investment in sexual behaviour, when maintained in the presence of females. Increasing ejaculate size in the absence of females could impose costs that would be paid when an opportunity to mate eventually arises. One of such costs may involve male post-copulatory competitiveness and may be associated with increased sperm senescence. To explore mismatch costs, firstly we induced two groups of males to differentiate their sperm production by exposing them or not to female stimuli. Then, we isolated them to prevent matings and have their sperm ageing. Finally, we compared ejaculate quality between the groups. Contrary to expectations, we found that female-stimulated males did not suffer from increased sperm senescence. These costs are probably minimized by the high level of plasticity associated with this trait, resulting in sperm production being quickly re-adjusted to a new environment. Other types of mismatch costs may be more relevant, for example, those related to trade-offs with sexual behaviour.

中文翻译：

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策略性射精调整和不匹配：男性是否支付精子衰老成本？

在许多物种中，雄性对精子的产生表现出预期的可塑性，它们会根据感知到的交配机会进行调整。虽然精子生产的战略调整可能是有益的，但它也可能与成本有关，包括那些与男性随后将经历的条件不匹配的表型表达所产生的成本。射精投资与其他性状投资之间的权衡以及个体射精性状之间的权衡加剧了错配成本。事实上，由于获得交配的能力受损或射精质量下降，权衡可能会导致男性竞争力下降。我们使用雄性孔雀鱼探索了错配成本，众所周知，雄性孔雀鱼会增加精子产量，但会减少它们对性行为的投资，在女性在场的情况下维持。在没有雌性的情况下增加射精大小可能会增加成本，而当最终出现交配机会时，这些成本将被支付。其中一项成本可能涉及男性交配后的竞争力，并且可能与精子衰老增加有关。为了探索错配成本，我们首先诱导两组雄性通过暴露或不暴露于雌性刺激来区分他们的精子产生。然后，我们将它们隔离以防止交配并使它们的精子老化。最后，我们比较了各组之间的射精质量。与预期相反，我们发现受女性刺激的男性并没有出现精子衰老增加的情况。这些成本可能通过与此特性相关的高度可塑性而最小化，导致精子生产迅速重新适应新环境。其他类型的错配成本可能更相关，例如，与性行为权衡相关的成本。