Nakata Kensuke, Shigemiya Yusuke
Faculty of Contemporary Society, Kyoto Women's University, Kyoto, Japan.
Faculty of Applied Information Technology, Nagasaki Institute of Applied Science, Nagasaki, Japan.
Proc Biol Sci. 2025 Jan;292(2039):20242722. doi: 10.1098/rspb.2024.2722. Epub 2025 Jan 29.
External female genital mutilation (EFGM) is a type of traumatic mating in which males damage female genitalia, resulting in the loss of female re-mating ability. This study examined whether sexual conflict underlies EFGM by examining the possible female reproductive costs from the decreased number of matings in spider, . The female typically receives sperm from a male twice during a mating bout. We manipulated both the number of matings and the number of male partners of females and compared their reproductive outputs. The results indicated that females receiving sperm three times-equivalent to one and a half matings from two males-laid more egg sacs with more eggs per egg sac than control females that received sperm twice from one male. The control females laid more egg sacs and fewer eggs per egg sac than females that received sperm once. There was no significant difference in reproductive output between the control females and females that received sperm twice from the two males. These results indicate that females benefit from multiple matings but not from mating with multiple males, supporting the sexual conflict hypothesis. Our study has implications for our understanding of the evolution of harmful mating.
女性外阴残割是一种创伤性交配行为，雄性会损伤雌性生殖器，导致雌性失去再次交配的能力。本研究通过研究蜘蛛因交配次数减少可能产生的雌性生殖成本，来探讨性冲突是否是女性外阴残割的潜在原因。在一次交配过程中，雌性通常会从雄性那里接收两次精子。我们控制了雌性的交配次数和雄性伴侣数量，并比较了它们的生殖产出。结果表明，接受三次精子的雌性——相当于与两只雄性进行了一次半交配——比从一只雄性那里接受两次精子的对照雌性产下了更多的卵囊，每个卵囊中的卵也更多。对照雌性比只接受一次精子的雌性产下的卵囊更多，但每个卵囊中的卵更少。接受两次精子的雌性（分别来自两只雄性）与对照雌性之间的生殖产出没有显著差异。这些结果表明，雌性从多次交配中受益，但并非从与多个雄性交配中受益，这支持了性冲突假说。我们的研究对我们理解有害交配的进化具有启示意义。
