Researchers in Japan have identified a courtship behavior between fruit flies that may help explain how environmental factors can alter the sexual orientation of individuals.

In a study featured in the journal Nature Communications, Daisuke Yamamoto, a professor of neurogenetics at Tohoku University, examined how the sexual behavior of male fruit flies is affected by the mutated version of the fruitless (fru) gene.

According to Yamamoto, the neurons responsible for expressing the fru gene help determine the entire aspect of sexual behavior in male individuals.

In his 30-year study of fruit fly sexual behavior, Yamamoto has observed that male flies normally would touch the abdomen of their prospective female partners in order to get a scent of their sex pheromones before they proceed with their mating.

Those that have the mutated fru gene, however, do not show any interest in mating with female flies. They tend to pursue other male flies instead.

Courtship Behavior Of Male Fruit Flies With The Mutant Fru Gene

For his latest research, Yamamoto sought to understand how the vision of fruit flies with or without the mutated fru gene impacts the insects' courtship behavior.

Together with his colleague, Soh Kohatsu, Yamamoto optically activated the neurons in the fruit flies' brain that are known to affect their decision-making when it comes to courtship. He did so by showing the insects a screen with flashing white spots, which were meant to represent female fruit flies that were walking.

Fruit flies that did not have the mutated fru gene had to be primed with pheromones before making any moves to pursue the white spots.

Those that had the altered gene, on the other hand, pursued the spots without the need of brain stimulation or priming through pheromones. They quickly went to follow the white spots around and even vibrated their wings, which is a common behavior during courtship.

What makes this behavior particularly interesting is that it was only seen in mutant fruit flies that were raised along with other flies. Male flies that were reared individually did not show any such behaviors toward the white spots.

Yamamoto said that this was a surprising discovery since he has always thought that courtship between male fruit flies with the mutated fru gene was purely genetically programmed.

The findings suggest that interaction between the insects plays a crucial role in activating the neurons that cause mutant males to become more hypersensitive to visual factors.

Yamamoto cautions other researchers in relating their findings on fruit fly sexual orientation with those of humans. However, he does agree that there are certain aspects of human sexual orientation that may have similarities to the mechanistic tendencies of the flies.

He said that their study provides a plausible explanation to how the relationship between nature and nurture helps determine the sexual orientation of humans.

Photo: John Tann | Flickr