How male flies’ courtship song ‘turns on’ female’s immune system

The rhythmic buzzing of a male fruit fly’s courtship song is an exciting sound for a female, as it literally turns her on.

Now, biologists at the University of St Andrews have discovered that a male’s song also turns on the genes related to the female’s immune system in a bid to ward off potential infections after mating.

Elina Immonen and Mike Ritchie wanted to understand what genes were “switched on” when a fly prepares to mate.

To investigate this, the team played female fruit flies a recording of the “song” that males produce by vibrating their wings. They then produced a read-out of the flies’ active genes.

This showed that when the female heard the courtship song of a male of the same species, she would “generally get excited”, the BBC quoted Prof Ritchie as saying.

For example, genes in the female’s antennae – which are essentially her ears – were “switched on”.

“But the big surprise was that genes involved in immune function were also switched on,” Prof Ritchie said.

“It appears that if she hears a sexy song, she knows she’s likely to mate soon, so she makes the physiological change to prepare for mating – that involves increasing the activity of immune genes,” he added.

Prof Ritchie explained that the female fruit flies had probably evolved to “cope” with the potential harm caused to them by mating.

The findings are reported in the Royal Society journal Proceedings B.

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