The timing of female genital mutilation and the role of contralateral palpal insertions in the spider Cyclosa argenteoalba

Sexual conflict underlying external female genital mutilation in spiders: assessing whether females benefit from multiple matings

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, Cyclosa argenteoalba. 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.

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 counteradaptations 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 counteradaptation to genital mutilation allowing females to mate multiply.