Lyons Kady, Chabot Chris L, Mull Christopher G, Paterson Holder Corinne N, Lowe Christopher G
California State University, Long Beach Long Beach CA USA.
California State University, Northridge Northridge CA USA.
Ecol Evol. 2017 Jun 15;7(15):5603-5612. doi: 10.1002/ece3.3086. eCollection 2017 Aug.
Polyandry resulting in multiply-sired litters has been documented in the majority of elasmobranch species examined to date. Although commonly observed, reasons for this mating system remain relatively obscure, especially in batoids. The round stingray () is an abundant, well-studied elasmobranch distributed throughout the northeastern Pacific that we used to explore hypotheses regarding multiple paternity in elasmobranchs. Twenty mid- to late-term pregnant females were sampled off the coast of southern California and their litters analyzed for the occurrence of multiple paternity using five nuclear microsatellite loci. In addition, embryo sizes and their position within the female reproductive system (i.e., right or left uterus) were recorded and used to make inferences for patterns of ovulation. Multiple paternity was observed in 90% of litters and male reproductive success within litters was relatively even among sires. High variability in testes mass was observed suggesting that sperm competition is high in this species, although male reproductive success per litter appeared to be relatively even. Using embryo size as a proxy for fertilization, females were found to exhibit a variety of ovulation patterns that could function to limit a male's access to eggs and possibly promote high rates of multiple paternity. Our study highlights that elasmobranch mating systems may be more varied and complex than presumed and further investigation is warranted.
在迄今为止所研究的大多数板鳃亚纲物种中，一妻多夫制导致一窝幼崽有多个父亲的情况已有记载。尽管这种情况很常见，但这种交配系统的原因仍相对模糊，尤其是在鲼形目鱼类中。圆犁头鳐是一种分布于东北太平洋、数量丰富且研究充分的板鳃亚纲鱼类，我们利用它来探究有关板鳃亚纲鱼类多重父权的假说。在南加利福尼亚海岸采集了20只怀孕中后期的雌性圆犁头鳐样本，并利用五个核微卫星基因座对它们的幼崽进行分析，以确定是否存在多重父权现象。此外，记录了胚胎大小及其在雌性生殖系统中的位置（即右子宫或左子宫），并据此推断排卵模式。在90%的幼崽中观察到了多重父权现象，并且一窝幼崽中雄性的繁殖成功率在各个父亲之间相对均匀。观察到睾丸质量存在高度变异性，这表明该物种的精子竞争激烈，尽管每窝幼崽中雄性的繁殖成功率似乎相对均匀。以胚胎大小作为受精的指标，发现雌性呈现出多种排卵模式，这些模式可能起到限制雄性接近卵子的作用，并可能促使多重父权发生率较高。我们的研究强调，板鳃亚纲鱼类的交配系统可能比推测的更加多样和复杂，有必要进行进一步的研究。
