In a sexual role-reversal first, researchers say they've discovered female cave-dwelling insects from Brazil that have penis-like organs and their male counterparts, which apparently have vaginas.

The copulation process of the insect, identified with the genus Neotrogla, can last a staggering 70 hours and involves the female inserting her rather elaborate "penis," or gynosome, into the male's vagina-like opening, through which he transfers back to the female nutritious seminal substances, along with semen, the study's lead, Kazunori Yoshizawa from Hokkaido University in Japan, said in a news release.

The research -- explained in a paper published April 17 in Cell Press' journal Current Biology -- revealed that after the female's gynosome is inserted into a male, inflates and numerous spines internally anchor the two insects together.

At one point, when the researchers attempted to pull a male and female apart during the unique coupling, the male's abdomen was ripped from the thorax without breaking the genital connection.

Rodrigo Ferreira from the Federal University of Lavras in Brazil was collecting data to better describe the insect species within its natural cave environment when he sent a few specimens to insect specialist Charles Lienhard in Geneva, who recognized them as a new genus.

Lienhard was also the one who first noted the female gynosome.

Yoshizawa joined the research effort later.

The recent findings, said Yoshizama, open many new directions scientists can take, as they seek to learn more about what sets the Neotrogla apart from so many other species in the world.

Then, among other topics, researchers may now gain new strategies for experimenting with sexual selection, conflict between the sexes and the evolution of sexual novelty, the researchers said.

"Although sex-role reversal has been identified in several different animals, Neotrogla is the only example in which the intromittent [male organ that delivers the sperm] is also reversed," said Yoshizawa.

"It will be important to unveil why, among many sex-role-reversed animals, only Neotrogla evolved the elaborated female penis," said fellow researcher Yoshitaka Kamimura from Japan's Keio University.