What makes a fruit fly sing

In the fruit fly world, only the boys sing love songs. But postdoctoral researcher J. Dylan Clyne has discovered that, with help, the girls can make music, too. They just have to lose their heads.

Clyne, a physiology fellow at the School of Medicine, and his Yale mentor, Gero Miesenbock (now at Oxford), suspected that the song circuit is present in females but lies dormant. Using a technique developed by Miesenbock, the pair used lasers to stimulate the neurons they guessed were controlling singing in males.

The results were encouraging, but not definitive enough. So the researchers tried decapitation.

This seems extreme, but it makes biological sense. In fruit flies, the song neurons are located not in the head but the thorax. The head contains command centers, Clyne explains, which control not only singing but other behaviors that could interfere with mating. "When you cut off the head, you're eliminating the command neurons," he says. "That increases the mating behavior." 

When the researchers tried activating the neurons in decapitated females, the technique worked beautifully. (The flies make songs by vibrating one wing—actually more like fiddling than singing.) "The female song has a slightly different tune," Clyne notes. "But the surprising thing is that they sing at all."

The findings, reported in the April 18 issue of Cell, show that "you don't need large sex differences in the brain to get large differences in behavior," Clyne says. "There seems to be a switch that's turned on in the males and off in the females."

That observation supports the notion that, in flies and in other species, "the neural system is more or less unisex, and then you have these different modules" that control behavior, he says. "From an engineering standpoint, it's a lot easier to give both sexes the same circuitry and just turn the switch off or on."

Clyne's next ambition: "Try to figure out where those switches are."