Researchers at Harvard Medical School have discovered that sex-specific behavior plays a significant role in the interactions between male and female fruit flies.

Neurobiology Professor Edward A. Kravitz, along with post-doctoral fellows Yick-Bun Chan and Maria de la Paz Fernandez, genetically altered either the sex of the cells that make the flies’ pheromones or the sex of the nerve cells in the brain, or both, in order to determine the effects of these changes on the sexes’ interactions with each other.

Normally, the interaction between two male fruit flies is characterized by aggression—particularly if food, light, or a potential mate is present at the scene. In turn, a male fruit fly will attempt to court a female fly by signaling with his wing and singing.

Throughout these interactions, male and female flies determine the other’s sex by employing different senses.

The “transformer gene”—which is only active in female tissues—can be turned on or off in either gender to manipulate the sex-specific taste and smell of the fly.

The researchers observed that when a male fly encountered a female genetically manipulated to exude a male “taste,” he would attempt to fight—instead of court—her.

A similar interaction was witnessed when a male fly met a female exhibiting male behavioral patterns as a result of a brain cell alteration—even if the female did not have other male tissues.

Kravitz said that he and his team had expected the change in taste and smell to alter the flies’ interactions.

What they did not expect, however, was the significance of behavioral change in the interactions.

“It makes the important point that the way an animal behaves is equally important as the way an animal looks, touches, and smells,” Kravitz said about his research. “It also shows you can completely switch the normative behavioral profiles so that males will court males or males will fight females.”

Kravitz said that the recent discoveries serve as evidence of the “complexity and biological unity that exists.”

When asked if this study could be extended to other types of animals in the future, Kravitz said that flies are unique because “the genetic tools are so powerful.”

“We can do manipulations in flies now that can’t be done in other species yet,” he added.