Researchers have discovered insects where the females have penis-like genitals, and males have vagina-like organs.
The little-known cave bugs were are the first known species with genitalia that reverse the traditional sex roles, a discovery that could help scientists figure out the conflict between the sexes in the animal kingdom, according to LiveScience.com.
Scientists found a structure similar to a penis on the female bugs, called a gynosome, which is made of membranes, ducts, spikes, and muscles, according to study released this week. The male's vagina-like genitals is called phallosomes.
"Neotrogla species constitute the first cases in nature in which genitalia are reversed," said Rodrigo Ferreira, a cave biologist from the Federal University of Lavras in Brazil who co-authored the study, according to LiveScience.com.
The insects, from the genus Neotrogla, were discovered in dry caves in Brazil over 18-years-ago. The ones with gynosomes are "a completely novel structure in evolution," said Kazunori Yoshizawa, an entomologist from Hokkaido University in Japan who led the study, according to LiveScience.com.
"Evolution of such novelties is exceptionally rare, maybe comparable with the origin of insect wings," Yoshizawa added.
Adult Neotrogla range from approximately 0.11 to 0.15-inches-long.
Scientists confirmed that the female gynosome is inserted into the male to collect capsules filled with sperm. The insect's sexual intercourse can last from 40 to 70 hours.
The gynosome is so strong that scientists determined when it is inside the male, it is close to impossible to separate the female and male insects.
The study was published this week in the journal Current Biology.
Scientists believe the reversed sex roles are a result of the environment they live in, according to LiveScience.com. The insects evolved to allow the females to reproduce due to the lack of natural resources in the caves.
"Longer matings can allow a higher amount of semen to be transferred," Ferreira said to LiveScience.com.
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