School of Biological Sciences, University of Canterbury, Christchurch, New Zealand.
Department of Anatomy, University of Otago, Dunedin, New Zealand.
Elife. 2017 Oct 31;6:e28811. doi: 10.7554/eLife.28811.
In many species, males can make rapid adjustments to ejaculate performance in response to sperm competition risk; however, the mechanisms behind these changes are not understood. Here, we manipulate male social status in an externally fertilising fish, chinook salmon (), and find that in less than 48 hr, males can upregulate sperm velocity when faced with an increased risk of sperm competition. Using a series of sperm manipulation and competition experiments, we show that rapid changes in sperm velocity are mediated by seminal fluid and the effect of seminal fluid on sperm velocity directly impacts paternity share and therefore reproductive success. These combined findings, completely consistent with sperm competition theory, provide unequivocal evidence that sperm competition risk drives plastic adjustment of ejaculate quality, that seminal fluid harbours the mechanism for the rapid adjustment of sperm velocity and that fitness benefits accrue to males from such adjustment.
在许多物种中，雄性可以迅速调整精液性能以应对精子竞争风险；然而，这些变化背后的机制尚不清楚。在这里，我们在一种外部受精的鱼类——奇努克鲑鱼（Oncorhynchus tshawytscha）中操纵雄性的社会地位，发现不到 48 小时，雄性在面临更高的精子竞争风险时可以提高精子速度。通过一系列的精子操作和竞争实验，我们表明，精子速度的快速变化是由精液介导的，而精液对精子速度的影响直接影响亲权份额，从而影响繁殖成功率。这些综合发现与精子竞争理论完全一致，无可置疑地证明了精子竞争风险驱动了精液质量的可塑性调整，精液中蕴藏着快速调整精子速度的机制，而这种调整对雄性有利。
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