Spiders that mutilate female genitalia after mating found

Certain male spiders mutilate genitalia of their female partners after mating, a new study reveals. Scientists say the behaviour is an adaptation for securing paternity.

The study, a first of its kind, published online in the 5 November issue of the journal Current Biology shows that some orb-weaving male spiders mechanically prevent female spiders from mating again. This means that all progeny of female orb-weaving spiders have the same father.

Orb-weaver spiders are the most common spiders that weave spiral wheel-shaped webs often found in garden. According to scientists, the phenomenon is widespread in orb-weaving spider but "overlooked" so far.

"In the orb-weaving spider (Larinia jeskovi) males remove the scapus, a crucial coupling device on the female external genital region," researchers at Zoological Institute and Museum at the University of Greifswald in Germany said in the report.

"Reconstruction of the coupling mechanism using micro-CT-scanned mating pairs revealed that several sclerites of the male genitalia interact to break off the scapus. Once it is removed, re-mating cannot occur due to mechanical coupling difficulties," they explained. "Mutilation of female genitalia prevents harmed females from re-mating."

Scientists said all female spiders that were allowed to mate in lab under observation were found to be mutilated at the end of the mating season. However, researchers suspect that 80 other species of spider also exhibit this phenomenon.