Fitzpatrick J L, Desjardins J K, Milligan N, Montgomerie R, Balshine S
Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1.
Biol Reprod. 2007 Aug;77(2):280-4. doi: 10.1095/biolreprod.106.059550. Epub 2007 Apr 25.
Theory predicts that males experiencing elevated levels of sperm competition will invest more in gonads and produce faster-swimming sperm. Although there is ample evidence in support of the first prediction, few studies have examined sperm swimming speed in relation to sperm competition. In this study, we tested these predictions from sperm competition theory by examining sperm characteristics in Telmatochromis vittatus, a small shell-brooding cichlid fish endemic to Lake Tanganyika. Males exhibit four different reproductive tactics: pirate, territorial, satellite, and sneaker. Pirate males temporarily displace all other competing males from a shell nest, whereas sneaker males always release sperm in the presence of territorial and satellite males. Due to the fact that sneakers spawn in the presence of another male, sneakers face the highest levels of sperm competition and pirates the lowest, whereas satellites and territorials experience intermediate levels. In accordance with predictions, sperm from sneakers swam faster than sperm from males adopting the other reproductive tactics, whereas sperm from pirates was slowest. Interestingly, we were unable to detect any variation in sperm tail length among these reproductive tactics. Thus, sperm competition appears to have influenced sperm energetics in this species without having any influence on sperm size.
理论预测，经历精子竞争水平升高的雄性会在性腺上投入更多，并产生游动速度更快的精子。尽管有大量证据支持第一个预测，但很少有研究考察精子游动速度与精子竞争的关系。在本研究中，我们通过研究坦噶尼喀湖特有的小型护壳丽鱼科鱼类细纹丽鱼的精子特征，来检验精子竞争理论的这些预测。雄性表现出四种不同的繁殖策略：掠夺者、领地型、卫星型和偷腥者。掠夺者雄性会暂时将所有其他竞争雄性从贝壳巢穴中赶走，而偷腥者雄性总是在领地型和卫星型雄性在场的情况下释放精子。由于偷腥者在另一个雄性在场的情况下产卵，所以偷腥者面临的精子竞争水平最高，掠夺者最低，而卫星型和领地型则处于中等水平。与预测一致，偷腥者的精子比采用其他繁殖策略的雄性的精子游动得更快，而掠夺者的精子最慢。有趣的是，我们未能检测到这些繁殖策略之间精子尾部长度的任何差异。因此，精子竞争似乎影响了该物种的精子能量学，而对精子大小没有任何影响。
