Data from: No support for cryptic choice by ovarian fluid in an external fertilizer

Whether the ovarian fluid represents a selective environment influencing cryptic female choice was tested using an external fertilizer experiencing intense sperm competition and large effects of ovarian fluid on sperm swimming behaviour - the Arctic charr (Salvelinus alpinus). We physically separated the ovarian fluid from the eggs of reproductively active females and reintroduced either their own ovarian fluid or fluid from another female to the eggs. The eggs were then fertilized in vitro in a replicated split-brood design with sperm from two males under synchronized sperm competition trials, while also measuring sperm velocity of the individual males in the individual ovarian fluids. We found large effects of males, but no effect of females (i.e., eggs) on paternity, determined from microsatellites. More important, we found no effect of ovarian fluid treatments on the relative paternity of the two competing males in each pair. This experimental setup does not provide support for the hypothesis that ovarian fluid plays an important role as medium for cryptic female choice in charr. Power-analyses revealed that our sample size is large enough to detect medium sized changes in relative paternity (medium-sized effect-sizes), but not large enough to detect small changes in relative paternity. More studies are needed before a conclusion can be drawn about ovarian fluid's potential influence on paternity under sperm competition - even in charr.

本研究以经历剧烈精子竞争、且卵巢液对精子游动行为具有显著调控效应的体外受精物种——北极红点鲑（Salvelinus alpinus）为实验对象，旨在验证卵巢液是否构成影响隐蔽雌性选择（cryptic female choice）的选择性环境。我们首先将卵巢液与繁殖活跃雌性的卵进行物理分离，随后将雌性自身的卵巢液或其他雌性的卵巢液重新回添至卵样中。随后采用重复分窝设计，在同步精子竞争实验中，利用两只雄性的精子对卵进行体外受精；同时，我们还分别测定了各雄性精子在对应个体卵巢液中的游动速度。本研究通过微卫星标记（microsatellites）分析父本归属，结果显示雄性个体对父本比例存在显著影响，但雌性（即卵）对父本比例无显著作用。更为关键的是，我们未发现卵巢液处理对每组竞争雄性的相对父本比例存在任何影响。本实验设计不支持“卵巢液作为隐蔽雌性选择的介质发挥重要功能”这一假说。功效分析（power-analyses）表明，本研究的样本量足以检测到中等效应量（effect-sizes）的相对父本比例变化，但不足以检测到微小效应量的变化。若要明确卵巢液在精子竞争条件下对父本比例的潜在影响——即便仅针对北极红点鲑——仍需开展更多相关研究方能得出定论。