Females of a cannibalistic spider control mutilation of their genitalia by males

When females can mate multiply, the interests of both sexes over female remating may not coincide, leading to selection for adaptations and counter-adaptations in males and females. In several orb-weaving spiders, males damage external structures of the female genitalia during copulation, which hinders the female from remating. We investigated whether females have control over the mutilation of their genitalia in the orb-weaving spider Larinia jeskovi. We found that female sexual cannibalism during copulation reduced the number of insertions a male was able to perform and hence limited the probability of genital mutilation by the male. Genital mutilation did not differ between treatments in which females experienced different availabilities of other males before the mating trial: males absent, males near the female ('vicinity group'), and males in the female's web ('web group'). However, traits of the mating male (size, condition) were significantly correlated with the occurrence of cannibalism during mating in 'web' and 'vicinity' treatments. These results suggest that females have control over mutilation by an early termination of mating, can respond to the availability of potential mates and can alter the probability of mutilation according to certain male traits. Female sexual cannibalism may represent a counter-adaptation to genital mutilation allowing females to mate multiply.

当雌性具备多次交配能力时，两性在雌性再交配相关的利益诉求往往存在冲突，这会驱动雄性与雌性分别演化出适应性特征与反适应性特征。在多种园蛛（orb-weaving spider）类群中，雄性会在交配过程中损伤雌性的外生殖器结构，以此阻碍雌性再次交配。本研究以园蛛类群耶氏肖蛸（Larinia jeskovi）为研究对象，探究雌性是否能够调控自身生殖器的毁损情况。研究结果显示，交配过程中的雌性性食同类（sexual cannibalism）行为会减少雄性能够完成的交配插入次数，进而限制了雄性实施生殖器毁损（genital mutilation）的概率。在交配实验前，雌性分别接触三种不同可获得性的其他雄性的处理组中（无雄性组、雄性位于雌性附近的"vicinity group"、雄性栖息于雌性蛛网内的"web group"），生殖器毁损的发生率并无显著差异。不过，在"web group"与"vicinity group"这两个处理组中，交配雄性的相关性状（体型、身体状况）与交配过程中性食同类行为的发生显著相关。上述结果表明，雌性可以通过提前终止交配来调控生殖器毁损的发生，能够响应潜在配偶的可获得性，并依据特定雄性性状改变生殖器毁损的发生概率。雌性的性食同类行为或许是针对生殖器毁损的一种反适应性策略，借此帮助雌性实现多次交配。