This female insect pulls out a ‘penis’ to enter the male ‘vagina’: ScienceAlert

This female insect pulls out a ‘penis’ to enter the male ‘vagina’: ScienceAlert

This female insect pulls out a ‘penis’ to enter the male ‘vagina’: ScienceAlert

The animal world abounds in delightfully weird genitaliaargonauts who detach his own arm carrying sperm and send him to find a female to mate with, male echidnas with four tipped penises. Some insects even have cocked their genitals to fight off predators.

In another remarkable arrangement, male and female woodlice living in caves Neotrogla (distant relatives of book lice) swapped typical genital structures, with females wielding protrusions and males possessing a cavity.

hyena and elephant females also have protruding lumps – elongated genitals called pseudo-penis – but the males of each species also continue to wear hanging parts.

Transparent and opaque protuberance.
Female woodlouse gynosome. (Kazunori Yoshizawa)

In the case of bat poo-eating woodlice, however, the males have a vagina-like indentation, into which the females insert their penis-like structure – called the gynosome – to latch onto and suck their sperm.

build on Previous searchHokkaido University entomologist Zixin Cheng and his colleagues used microcomputer tomography to create 3D models of mating winged insects in caves in Brazil, to determine how these structures function and perhaps determine how this complete genital inversion occurred.

They confirmed that unlike other protruding female genitalia such as pseudo-penis, the gynosome is a more complex organ with specific muscles and pipes to match its unique suction purpose.

Using hooks at the base of the gynosome, females can cling to males for a surprisingly long time – up to 70 hours, in fact.

A set of muscles help the gynosome expand and enter the male, where it swells with the semen it sucks in. Another set of muscles then contracts the organ so that it can deposit the sperm into a pair of storage slots inside the female’s body.

“This unique feature makes female-to-female competition more intense, promoting the evolution of a female penis,” the team written in their diary.

Transparent organ with swollen end
Swollen female woodlouse gynosome. (Kazunori Yoshizawa/Hokkaido University)

With two sperm storage organs, Neotrogla females can store double the amount of sperm. This extra storage may provide a clue as to why insects are so active in their efforts to find sperm.

Sperm is packed in nutrient filled spermatophores. In resource-poor cave environments, these nutrients could serve another vital purpose. In addition, females have been observed extract nutritious semen packets even when they are too young to breed.

“The most likely explanation is that [evolution of] the female penis has been promoted by sexual selection to receive more seminal nutrition,” Cheng and colleagues Explain.

The females may be sucking the males for food, the team suspects.

The nuptial donation of nutrients by spermatophores is known from other insectsbut one would have to trace what happens to the male offering within the female to confirm this.

The lack of reliable food in Brazilian caves “is likely a major factor facilitating the evolution of sex role reversals,” according to entomologist and lead author Kazunori Yoshizawa of Hokkaido University in Japan. explained to them New York Times.

This research was published in Royal Society Open Science.

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