An Oxford scientist has used mind control to make female flies belt out male love songs, revealing they have a hidden capacity for masculine behaviour.
The research, which suggests that the sexes are not quite so different as they seem, exploits a remote control method that could provide revolutionary insights into behaviour.
Professor Gero Miesenböck of Oxford University is sometimes nicknamed the "lord of the flies" after remarkable work he pioneered in America to use laser light to control fly brains with the flick of a switch. He has now applied his mind control methods to exploring fly sexuality.
Three years ago, he caused a buzz when he showed he could trigger certain actions in flies from a distance by shining light on them. The flies are genetically engineered so that only the brain cells of interest were made responsive to light.
When the laser flashed it activated these brain cells and could make flies jump, walk, fly or, in the present case, produce a 'love song'.
Male fruit flies usually 'sing' to attract females, vibrating one wing to produce a distinctive sound which females like because they then allow copulation.
By tweaking one set of nerve cells thought to control this behaviour, the so called fru neurons, Professor Miesenböck has shown that female fruit flies can be made to 'sing' too.
"You might expect that the brains of the two sexes would be built differently, but that does not seem to be the case," says Prof Miesenböck. "Instead, it appears there is a largely bisexual or 'unisex brain' with a few critical switches that make the difference between male and female behaviour."
"The fact that we could make females vibrate one wing to produce a courtship song - a behaviour never before seen in female flies - shows that the brain circuits for this male behaviour are present in the female brain, even though they are never used for that purpose,' says Miesenböck.
Although the work suggests the circuitry for male behaviour exists in female brains and simply lies dormant, the 'song' was not quite as good as the males'.
"If you look carefully, the females do sound different," he says. "They have a different pitch and rhythm and aren't as well controlled." He thinks those distinctions probably stem from real, if subtle, differences between the male and female brains.
Despite this off key note, the study poses a profound puzzle. "The mystery at the root of our study is the neuronal basis of differences in male and female behaviour. Anatomically, the differences are subtle. How is it that the neural equipment is so similar, but the sexes behave so differently?
The new findings suggest that flies must harbour key nodes or "master switches" that set the whole brain to the male or female mode, according to the researchers. Their next goal is to find those controls.