Data from: Effects of ovarian fluid and genetic differences on sperm performance and fertilization success of alternative reproductive tactics in Chinook salmon

In many species, sperm velocity affects variation in the outcome of male competitive fertilization success. In fishes, ovarian fluid (OF) released with the eggs can increase male sperm velocity and potentially facilitate cryptic female choice for males of specific phenotypes and/or genotypes. Therefore, to investigate the role of OF on fertilization success, we measured sperm velocity and conducted in vitro competitive fertilizations with paired Chinook salmon (Oncorhynchus tshawytscha) males representing two alternative reproductive tactics, jacks (small sneaker males) and hooknoses (large guarding males), in the presence of river water alone and OF mixed with river water. To determine the role of genetic differences on fertilization success, we genotyped fish at neutral (microsatellites) and functional [major histocompatibility complex (MHC) II ß1] markers. We found that when sperm were competed in river water, jacks sired significantly more offspring than hooknoses, however, in OF there was no difference in paternity between the tactics. Sperm velocity was significantly correlated with paternity success in river water but not in ovarian fluid. Paternity success in OF, but not in river water alone, was correlated with genetic relatedness between male and female, where males that were less related to the female attained greater paternity. We found no relationship between MHC II ß1 divergence between mates and paternity success in water or OF. Our results indicate that OF can influence the outcome of sperm competition in Chinook salmon, where OF provides both male tactics with fertilization opportunities, which may in part explain what maintains both tactics in nature.

在众多物种中，精子运动速度会影响雄性竞争性受精结局的差异。在鱼类中，与卵子一同释放的卵巢液（ovarian fluid, OF）可提升雄性精子的运动速度，并可能助力特定表型和/或基因型雄性的隐蔽雌性选择。因此，为探究卵巢液对受精成功的作用，我们测定了精子运动速度，并开展了体外竞争性受精实验：实验选用代表两种不同繁殖策略的成对奇努克鲑（Oncorhynchus tshawytscha）雄性——小型偷配雄性（jacks）与大型护巢雄性（hooknoses），分别在仅含河水以及河水与卵巢液混合的两种环境下进行实验。为明确遗传差异对受精成功的影响，我们对实验鱼进行了中性标记（微卫星）以及功能标记[主要组织相容性复合体（major histocompatibility complex, MHC）II β1]的基因分型。我们发现，当精子在河水中竞争时，小型偷配雄性的子代繁育量显著高于大型护巢雄性；但在卵巢液环境中，两种繁殖策略的雄性父权成功率并无显著差异。河水中的精子运动速度与父权成功率显著相关，但在卵巢液环境中则无此关联。仅在卵巢液环境中，父权成功率与雌雄个体间的遗传亲缘度相关：与雌性亲缘关系越远的雄性，其获得的父权成功率越高；而单纯河水环境中则无此关联。我们未发现配偶间主要组织相容性复合体II β1的序列差异与河水或卵巢液环境中的父权成功率存在关联。本研究结果表明，卵巢液能够影响奇努克鲑的精子竞争结局，可为两种繁殖策略的雄性均提供受精机会，这或许可以部分解释为何自然界中这两种繁殖策略得以共存。