The female insect with a 'penis' developed new muscles to help it penetrate males and steal their sperm

Embargoed until: Publicly released: 2023-01-11 11:01

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A species of cave insect from Brazil called Neotrogla, in which the females have the 'penis', developed muscles allowing them to penetrate the vagina-like genitalia of males during sex, according to international scientists. The team used 3D X-rays to compare the anatomy of the insects with their closest relatives. They found the muscles that allow its 'gynosome' - the scientific term for a female willy - to protrude and retract were present in related species with non-protrudable gynosomes, suggesting they evolved before the insects' sex roles were reversed. The muscles may have originally served to allow females to stimulate males so they would release semen during sex, providing the females with a nutritious semen snack, the researchers say.

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From: The Royal Society

Acquisition of novel muscles enabled protruding and retracting mechanisms of female penis in sex-role reversed cave insects

By using the µCT technique, two groups of novel muscles related to the protrusion and retraction of gynosomes (female penis) were discovered. These muscles were also observed in species having a primitive, nonprotrutable gynosome (prepenis). This strongly suggests that evolution of these muscles preceded the acquisition of the protruding function of the gynosome, originally having a putative stimulatory function to receive nutritious semen. This intermediate stage probably allowed for the reversal of genital functions.

Bugs and gynae - Researchers have discovered muscles that help the female penis (gynosome) in some insects protrude and retract. 3D imaging of Brazilian sex-role reversed cave insects showed two groups of muscles related to the protrusion and retraction of gynosomes. These were also observed in species with a primitive, non-protrusible gynosome. This suggests the muscles evolved before gynosome protrusion, which is thought to stimulate males in order to receive nutritious semen, the authors said.

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Research The Royal Society, Web page The URL will go live at some point after the embargo ends

Journal/
conference: Royal Society Open Science

Research:Paper

Organisation/s: Hokkaido University, Japan

Funder: This study was funded by JSPS 15H04409 and 19H03278 to K.Y.; JSPS 20J2088301 to C.Z.; CNPq 304682/2014-4 to R.L.F.

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