Simmons Leigh W, Denholm Amy, Jackson Chantelle, Levy Esther, Madon Ewa
Centre for Evolutionary Biology, School of Animal Biology (M092), The University of Western Australia, Crawley, Western Australia 6009, Australia.
Biol Lett. 2007 Oct 22;3(5):520-2. doi: 10.1098/rsbl.2007.0328.
Sperm competition theory predicts that males should increase their expenditure on the ejaculate with increasing risk of sperm competition, but decrease their expenditure with increasing intensity. There is accumulating evidence for sperm competition theory, based on examinations of testes size and/or the numbers of sperm ejaculated. However, recent studies suggest that ejaculate quality can also be subject to selection by sperm competition. We used experimental manipulations of the risk and intensity of sperm competition in the cricket, Teleogryllus oceanicus. We found that males produced ejaculates with a greater percentage of live sperm when they had encountered a rival male prior to mating. However, when mating with a female that presented a high intensity of sperm competition, males did not respond to risk, but produced ejaculates with a reduced percentage of live sperm. Our data suggest that males exhibit a fine-tuned hierarchy of responses to these cues of sperm competition.
精子竞争理论预测，随着精子竞争风险的增加，雄性应该增加其在射精上的投入，但随着竞争强度的增加则应减少投入。基于对睾丸大小和/或射精精子数量的研究，有越来越多的证据支持精子竞争理论。然而，最近的研究表明，射精质量也可能受到精子竞争的选择。我们对海洋长颚蟋精子竞争的风险和强度进行了实验操控。我们发现，雄性在交配前遇到竞争对手时，所产生的射精中活精子的比例更高。然而，当与呈现高强度精子竞争的雌性交配时，雄性对风险没有反应，而是产生了活精子比例降低的射精。我们的数据表明，雄性对这些精子竞争线索表现出了精细调整的反应层级。
