In many species, males can rapidly adjust their ejaculate performance in response to changing levels of sperm competition, an ability that is probably mediated by seminal fluid adaptive plasticity. In the black goby, Gobius niger, territorial males attach viscous ejaculate trails to the nest roof, from which sperm are slowly released into the water during the long-lasting spawning events. Sneaker males release their sperm in the vicinity of the nest, and territorial males try to keep them at a distance by patrolling their territory. We show here that territorial males' ejaculate trails released a higher proportion of their sperm in the presence of a single sneaker, but this proportion decreased when there were three sneakers, an effect that is most likely mediated by a change in the seminal fluid composition. Field observations showed that when multiple sneaking attempts occurred, territorial males spent more time outside the nest, suggesting that ejaculation rate and territory defence are traded-off. Altogether, these results suggest that the adjustment of sperm release from the ejaculate may be strategic, guaranteeing a more continuous concentration of the territorial male's sperm in the nest, although at a lower level, when he is engaged in prolonged territory defence outside the nest.

在许多物种中，雄性可以根据精子竞争水平的变化迅速调整射精性能，这种能力可能是由精液适应性可塑性介导的。在黑虾虎鱼中，Gobius niger，领地雄性将粘稠的射精轨迹附着在巢顶上，在持续的产卵过程中，精子从那里缓慢地释放到水中。运动鞋雄性在巢附近释放它们的精子，而领地雄性则试图通过巡逻它们的领地来与它们保持距离。我们在这里展示了在单只运动鞋的情况下，领地男性的射精轨迹释放了更高比例的精子，但当有三双运动鞋时，这一比例下降，这种影响很可能是由精液成分的变化介导的。实地观察表明，当发生多次偷偷摸摸的尝试时，领地雄性在巢外停留的时间更长，这表明射精率和领地防御是相互权衡的。共，