Section of Integrative Biology, University of Texas at Austin, TX 78712, USA.
Gen Comp Endocrinol. 2011 Jan 15;170(2):381-90. doi: 10.1016/j.ygcen.2010.10.012. Epub 2010 Oct 25.
Estrogen is associated with female sexual behaviors, particularly receptive behaviors during the reproductive cycle. Less is known about the relationship between estrogen and female preference behaviors that may precede receptivity and copulation. Separating the mechanisms underlying preference from receptivity is often confounded by the tightly coupled cycle- or estrogen-dependent expression of female sexual behaviors. Here we utilize a live-bearing poeciliid (Xiphophorus nigrensis), a model species for studying the evolution of female mate choice that can store sperm over multiple brood cycles. We assayed estradiol along with preference, receptivity and locomotor behaviors in gestating females and then re-tested these females on days 1, 7, 14, 21, and 28 post-parturition. With a posteriori reproductive cycle assessment, we asked whether reproductive state predicts differences in (i) estradiol levels, and (ii) behaviors (preference, receptivity, and general locomotor activity). We then examined if estradiol levels (independent of reproductive state) explain any variation in these behaviors. We found that endogenous estradiol levels vary across the reproductive cycle: gestating females had lower estradiol levels than those undergoing vitellogenesis/fertilization. In contrast, receptivity and preference behaviors did not vary over the reproductive cycle. Estradiol levels did not predict variation in receptive behavior, but were associated with increased locomotion. While individual female preference behaviors were consistent across the reproductive cycle, there was a small negative relationship between estradiol and preference behaviors explaining between 3% and 10% of the inter-female variation in preference behavior. Our data indicate X. nigrensis females may exhibit a facultatively dissociated reproductive system.
雌激素与女性的性行为有关，尤其是在生殖周期中接受性行为。关于雌激素与可能先于接受和交配的女性偏好行为之间的关系，人们了解得较少。将偏好的机制与接受能力分开，往往会因雌性性行为的紧密耦合周期或雌激素依赖性表达而变得复杂。在这里，我们利用一种胎生的脂鲤科鱼类（Xiphophorus nigrensis），这是一种研究雌性配偶选择进化的模型物种，它可以在多个繁殖周期中储存精子。我们在妊娠雌鱼中检测了雌二醇以及偏好、接受和运动行为，然后在产后第 1、7、14、21 和 28 天对这些雌鱼进行了重新测试。通过对生殖周期的后评估，我们询问了生殖状态是否可以预测（i）雌二醇水平，以及（ii）行为（偏好、接受和一般运动活动）的差异。然后，我们检查了雌二醇水平（与生殖状态无关）是否可以解释这些行为的任何变化。我们发现，内源性雌二醇水平在生殖周期中发生变化：妊娠雌鱼的雌二醇水平低于进行卵黄生成/受精的雌鱼。相反，接受和偏好行为在生殖周期中没有变化。雌二醇水平不能预测接受行为的变化，但与运动增加有关。虽然个体雌鱼的偏好行为在整个生殖周期中保持一致，但雌二醇与偏好行为之间存在很小的负相关关系，解释了偏好行为中 3%至 10%的雌鱼间变异。我们的数据表明，X. nigrensis 雌鱼可能表现出一种可有可无的分离生殖系统。
