Securing Paternity by Mutilating Female Genitalia in Spiders

Area of Science:

• Evolutionary biology
• Animal behavior
• Reproductive strategies

Background:

• Male competition for paternity drives diverse reproductive strategies.
• Sperm competition can lead to adaptations like guarding, chemical manipulation, or physical plugs.
• Genital damage during mating is often a collateral effect, not a direct paternity strategy.

Purpose of the Study:

• To investigate a drastic paternity-securing mechanism in Larinia jeskovi spiders.
• To document the removal of female genital coupling structures by males.
• To assess the prevalence and evolutionary implications of male-inflicted genital mutilation.

Main Methods:

• Observation of mating behavior in Larinia jeskovi.
• Micro-computed tomography (micro-CT) scanning of mating pairs to reconstruct genital interactions.
• Field surveys to determine the prevalence of female genital mutilation.

Main Results:

• Male Larinia jeskovi spiders actively remove the scapus, a female genital coupling device.
• This removal prevents subsequent mating by making mechanical coupling impossible.
• All female L. jeskovi examined at the end of the mating season showed signs of genital mutilation.
• Male genital manipulation is suspected in at least 80 additional spider species.

Conclusions:

• Male removal of female genital structures is a direct and effective paternity assurance mechanism.
• This phenomenon, termed external genital mutilation, is likely widespread in spiders.
• Interlocking genitalia provide an evolutionary basis for such drastic male adaptations, potentially occurring in other animal groups.