Bizarre Gender-Bender Bugs Baffle Scientists

Credit: Richard Naylor

Scientists have discovered a real gender-bender of a bug, a species in which most females impersonate males.

Past research had already revealed the male bugs possessed fake female genitalia.

"We ended up uncovering a hotbed of deception," said evolutionary biologist Klaus Reinhardt at the University of Sheffield in England. "Nothing like this exists anywhere else in the animal kingdom."

Reinhardt and his colleagues investigated remote and dangerous bat caves in East Africa for the bloodsucking African bat bug (Afrocimex constrictus), a close relative of the bed bug. The bats were reportedly hosts for Ebola and other lethal viruses.

"We had to work in containment suits with full-faced respirators in sweltering temperatures for hours at end," Reinhardt said.

Sex among bat bugs (as with bed bugs) is violent. During copulation, males of these species pierce the abdomens of their mates with their genitals and ejaculate directly into their blood.

The researchers originally set out to investigate bat bugs in the hopes of shedding light on "one of nature's strangest phenomena — why males had female genitalia," Reinhardt said.

Unlike bed bugs, male African bat bugs have bogus female genitals—a fact the scientists freely call "bizarre." Past research found they mate with each other as well as with females. Although the sham genitals are convincingly intricate, they do not have a covering over them as real female genitals do.

Surprisingly, the scientists have now discovered that female African bat bugs practiced gender-bending also by impersonating males. Only one out of six females possessed conventional female genitals, while the rest had genitals resembling the fakes seen on males.

By masquerading as males, females enjoy less sexual attention. Given that sex leads to wounding in these bugs, Reinhardt and his colleagues suggest avoiding the trauma of sex makes sense. Indeed, the researchers discovered females that impersonated males had far less fewer than more conventional females.

As to why any females still retain conventional genitalia given the wounds they accrue—"no idea," Reinhardt told LiveScience. Normal females might lay more eggs, "but in order to address this question you would need controlled lab studies, and we have not yet succeeded in breeding these animals."

It also remains a mystery as to why males possess sham female genitals. Scientists think the males might genitally stab any adult bat bug, so one conjecture as to why males evolved bogus female genitals involves guiding stabs to relatively safe parts of the anatomy.

"Our results suggest that the battle of the sexes is a very powerful evolutionary force which can result in very bizarre adaptations," Reinhardt said.

Reinhardt and his colleagues will detail their findings in a forthcoming issue of the journal American Naturalist.

• Image Gallery: Backyard Bugs
• Top 10: Secret Weapons
• All About Insects