Of lice and men: Female insect grows a penis to get her man
Scientists thrilled by 'extraordinarily rare' adaption found in southern African caves
The idea of a woman getting her hooks into a man has found practical expression in cave-dwelling insects in southern Africa.
The female Afrotrogla bark louse has evolved a hook-shaped erectable penis that ensures her breeding partner cannot escape before a sufficient amount of sperm has been collected. This can take up to 70 hours.
The independent evolution of female penises in bark lice in Namibia and South America was “an extraordinarily rare event”, scientists from Japan, Brazil and Switzerland said in the journal Biology Letters.
They said it was probably due to the shortage of food in the dry caves where the lice lived, meaning males were more interested in finding a meal than a mate and semen became an alternative source of nutrition for females.
Hungry females became the initiators of mating as they competed for the semen, produced in large amounts by the male lice relative to their size.
This led to the development of two different female penises in Afrotrogla and its Brazilian cousin Neotrogla, which suck males dry over up to 70 hours.
Lead researcher Kazunori Yoshizawa, from Hokkaido University, said the “seminal gift” was rich in nourishment and an incentive for females to force males into mating.
“One of the important functions of penis and vagina is probably the secure delivery of semen in nonaquatic environments,” Yoshizawa explained.
“However, I think sexual selection is a more important factor for the evolution of the male penis, because not all terrestrial animals possess it. For example, many birds do not have a penis.
“Under typical sexual selection in which females are choosy and males are courting, the male penis has evolved many times independently, probably for active and sometimes coercive mating.
“A simple reversal of gender roles in sexual selection, however, cannot simply cause the reversed genital organs.”
The new paper follows an earlier one in 2014 announcing the Neotrogla find. In 2017, Yoshizawa and his colleagues won the spoof Ig Nobel biology prize for their discovery.