Butts Ian A E, Prokopchuk Galina, Kašpar Vojtěch, Cosson Jacky, Pitcher Trevor E
School of Fisheries, Aquaculture, and Aquatic Sciences, Auburn University, Auburn, AL 36849, USA
Biology Centre, Institute of Parasitology, Czech Academy of Sciences, České Budějovice 370 05, Czech Republic.
J Exp Biol. 2017 Jun 15;220(Pt 12):2210-2217. doi: 10.1242/jeb.154195.
Alternative reproductive tactics (ARTs) are prevalent in nature, where smaller parasitic males typically have better sperm quality than larger territorial guard males. At present, it is unclear what is causing this phenomenon. Our objective was to gain insights into sperm form and function by examining flagellar beating patterns (beat frequency, wave amplitude, bend length, bend angle, wave velocity) and biomechanical sperm metrics (velocity, hydrodynamic power output, propulsive efficiency) of wild spawning Chinook salmon ARTs. Ovarian fluid and milt were collected to form a series of eight experimental blocks, each composed of ovarian fluid from a unique female and sperm from a unique pair of parasitic jack and guard hooknose males. Sperm from each ART were activated in river water and ovarian fluid. Flagellar parameters were evaluated from recordings using high-speed video microscopy and biomechanical metrics were quantified. We show that ART has an impact on flagellar beating, where jacks had a higher bend length and bend angle than hooknoses. Activation media also impacted the pattern of flagellar parameters, such that beat frequency, wave velocity and bend angle declined, while wave amplitude of flagella increased when ovarian fluid was incorporated into activation media. Furthermore, we found that sperm from jacks swam faster than those from hooknoses and required less hydrodynamic power output to propel themselves in river water and ovarian fluid. Jack sperm were also more efficient at swimming than hooknose sperm, and propulsive efficiency increased when cells were activated in ovarian fluid. The results demonstrate that sperm biomechanics may be driving divergence in competitive reproductive success between ARTs.
替代生殖策略（ARTs）在自然界中很普遍，较小的寄生性雄鱼通常比体型较大的领地守卫雄鱼具有更好的精子质量。目前，尚不清楚导致这种现象的原因。我们的目标是通过检查野生产卵奇努克鲑鱼替代生殖策略的鞭毛摆动模式（摆动频率、波幅、弯曲长度、弯曲角度、波速）和生物力学精子指标（速度、流体动力功率输出、推进效率）来深入了解精子的形态和功能。收集卵巢液和精液以形成一系列八个实验样本组，每个样本组由来自独特雌鱼的卵巢液以及来自一对独特的寄生雄鱼和守卫雄鱼的精子组成。将来自每种替代生殖策略的精子在河水和卵巢液中激活。使用高速视频显微镜从记录中评估鞭毛参数，并对生物力学指标进行量化。我们发现替代生殖策略对鞭毛摆动有影响，寄生雄鱼的弯曲长度和弯曲角度比守卫雄鱼更高。激活介质也影响鞭毛参数模式，当卵巢液加入激活介质时，摆动频率、波速和弯曲角度下降，而鞭毛的波幅增加。此外，我们发现寄生雄鱼的精子在河水中和卵巢液中的游动速度比守卫雄鱼的精子更快，并且推动自身游动所需的流体动力功率输出更少。寄生雄鱼的精子在游动时也比守卫雄鱼的精子更高效，并且当细胞在卵巢液中被激活时推进效率会提高。结果表明，精子生物力学可能是导致替代生殖策略在竞争性繁殖成功方面产生差异的原因。
