Female genital mutilation as a novel mating strategy in spiders: conflict or cooperation?
Evolution, Anthropology
Systematics and Morphology (Zoology)
Final Report Abstract
Reproductive interests between males and females do not fully coincide, resulting in sexual conflict. We aimed at understanding a seemingly extreme case of conflict, the mutilation of the female genitalia by the male, a phenomenon that is suspected to occur in more than 80 different spider species. In order to reveal the causes and consequences as well as the scenarios under with mutilation occurs we focused on Larinia jeskovi, an orb‐weaving spider that is found in large enough numbers in the Biebrza National Park, Poland. We discovered that mutilation in L. jeskovi is indeed related to copulation, and that the male genitalia (transformed extremities called pedipalps) possess structures that grasp a structure called scapus on the female genital area and remove it. The copulatory mechanisms in other araneids is also achieved by these accessory sclerites which led us to conclude that the mechanisms represents a pre‐adaptation to mutilation. In staged mating trials, we established that the scapus can only be removed if the male inserts both of his pedipalps, thereby cutting the scapus from both sides. Since males use their pedipalps sequentially, there is potential for female mate choice by allowing males to remove the scapus or not. The criteria of mate choice remain to be explored. Once the scapus is removed, the female cannot remate. Consequently, mutilating males sire all offspring that the female produces, however, only if they mate with a virgin female. Non‐virgin females discriminated against the first male, kept their scapus and are able to remate with a subsequent male that may not sire all offspring. The assessment of the degree of multiple paternity under natural conditions is still pending due to difficulties with establishing genetic markers for paternity analysis. This is due to the fact that the population in the Biebrza NP is genetically relatively homogeneous which requires a large number of markers. We try to remedy this problem by establishing an approach that combines microsatellite analysis and SNPs. We further investigated if females incur costs from being mutilated by studying oxidative stress. There was no apparent effect of mutilation on ROS. Finally, we investigated the conditions under which mutilation can evolve and be maintained. Using a game theoretical model we could show that this seemingly drastic behaviour can invade a population that exhibits last‐male sperm priority and a high encounter rate between the sexes. Interestingly, mutilation can evolve even if it is highly costly to females. National Geographic: This Spider Destroys Female Genitalia to Prevent Future Mating. November 5, 2015 National Geographic: Bondage, Cannibalism, and Castration — Spiders’ Wild Sex Lives. February 14, 2017 Le Monde (Supplément Sciences et Médecines): L’araignée mâle, un très mauvais coup. November 18, 2015 Die Welt: Spinnenmännchen verstümmeln weibliche Genitalien nach Sex. November 6, 2015 Tech Times: This male spider mutilates female genitalia to stop future mating. November 9, 2015 International Business Times: Spiders that mutilate female genitalia after mating found. November 7, 2015 Law and order: Spider victims unit: https://www.youtube.com/watch?v=Ej2G8ahLCPo Uhl Lab: https://www.youtube.com/watch?v=hMZkVq6fuIE
Publications
- 2015: Securing paternity by mutilating female genitalia in spiders. Current Biology 25, 2980‐2984
Mouginot, P.; Prügel, J.; Thom, U.; Steinhoff, P. O.; Kupryjanowicz, J.; & Uhl, G.
(See online at https://doi.org/10.1016/j.cub.2015.09.074) - 2017: Evolution of external female genital mutilation: why do males harm their mates? Royal Society Open Science 4, 171195
Mouginot, P.; Uhl, G.; & Fromhage, L.
(See online at https://doi.org/10.1098/rsos.171195)
