Without pheromones, fruit flies are lusty lotharios

By Brendan Kennedy
Toronto Star

Fruit fly on a rotten apple
Fruit fly on a rotten apple

By genetically tweaking fruit flies so they couldn't produce pheromones, University of Toronto scientists set off what they called a "sexual tsunami" that makes flies utterly irresistible to each other.

The new, pheromone-free bugs became so attractive, in fact, they lured mates of the same sex and of other fly species. That spurred pheromone-producing male flies to pursue the pheromone-free flies, even when the flies belonged to different species.

The study identified a hydrocarbon as being responsible for both sexual and species recognition, said lead researcher Joel Levine.

By removing the cells that create the hydrocarbon, researchers removed the flies' means of distinguishing and classifying each other, setting off uncontrollable waves of insect love.

The study, published Thursday in the science journal Nature, looked at how fruit flies — specifically, the Drosophila melanogaster — recognize sex and species.

"When you meet somebody, you immediately begin to figure out who they are," Levine said. "The same is true for flies and other animals."

Removing the pheromones also removed a female fruit fly's ability to adjust her response to a prospective mate. The female typically adjusts her sexual signals to become more or less appealing, Levine said. "Having that ability allows her to make a choice, otherwise, (the male fruit fly) wants one thing, and he's going for it."

The fact that the flies became attracted to each other regardless of gender also showed that the way individuals perceive one another doesn't necessarily correspond to one's sex, Levine said.

Levine, who studies the genetic basis of social behaviour, scuttled any notion that the study has a direct human correlation.

"We're hoping that as we understand more about how these things are communicated, we might get some insight in other species, too."

October 17, 2009 — Return to cover.