The wildlife is full of adorable strange genitalsfrom Argonauts that sever her own sperm-carrying arm and send it off to find a female to mate with Echidna males with four pointed penises. Some insects even have armed their genitals fight predators.
In another prominent arrangement, male and female barklice who live in burrows Neotrogla (distant relatives of booklice) have reversed typical genital structures, with females having protruding parts and males having a cavity.
hyena and elephant Females also have prominent dentition – called elongated genitalia Pseudo-penis – but males of all species continue to carry dangling parts.
Female barklice gynosome.
In the case of bat poop-eating barklices, however, the males have a vagina-like cavity into which the females insert their penis-like structure — called the gynosome — to hook onto and suck up their sperm.
Based on previous researchHokkaido University entomologist Zixin Cheng and colleagues used micro-computed tomography to create 3D models of copulating winged insects from caves in Brazil to understand how these structures work and perhaps determine how this full genital reversal came about.
They confirmed that, unlike other protruding female genitalia such as pseudo-penis, the gynosome is a more complex organ with specific muscles and tubes to accommodate its unique sucking purpose.
Using hooks at the base of the gynosome, females can cling to males for an alarmingly long time—up to 70 hours, in fact.
A set of muscles helps the gynosome unfold and enter the male, where it inflates itself with the sperm it has sucked up. Another set of muscles then contracts the organ so it can deposit the sperm into two storage slots in the woman’s body.
“This unique feature makes competition between women more intense and favors the development of a female penis,” the team said writes in her newspaper.
Inflated female Barklice gynosome. (Kazunori Yoshizawa/University of Hokkaido)
With two sperm storage organs, Neotrogla females can stock up on twice the amount of sperm. This extra storage could provide a clue as to why the insects are so active in their efforts to find seeds.
The semen is delivered packed with nutrients spermatophores. In resource-poor cave environments, these nutrients could serve another important purpose. Females were also observed Extracting the nutritious sperm packets even if they are too young to reproduce.
“That’s the most likely explanation [evolution of] the female penis was promoted through sexual selection to receive more seed nourishment,” Cheng and colleagues to explain.
The team suspects that the females suckle the males to eat.
The nuptial delivery of nutrients by spermatophores is known in other insectsbut to confirm this would require tracing what happens to the male offering within the female.
The lack of reliable food in Brazilian caves “is probably a major factor facilitating the development of gender role reversal,” according to entomologist and senior author Kazunori Yoshizawa of Hokkaido University in Japan declares to The New York Times.
This study was published in Open Science of the Royal Society.
