Unveiling the Genetic Basis of Mating Behavior in Fruit Flies

The way fruit flies mate could be crucial to preventing mosquitoes from spreading disease.

According to a recent study by researchers at the University of Iowa, a gene that controls the antenna movements of female fruit flies is essential for their ability to recognize the distinct sound made by potential male mates.

According to Iowa researchers, that gene is found in mosquitoes and can be silenced, which theoretically would reduce the likelihood of mating and thereby restrict the growth of mosquito populations.

It is commonly known that mosquitoes are carriers of numerous illnesses that harm people's health. These illnesses include Zika, Eastern equine encephalitis, and West Nile virus in the US. When female mosquitoes bite humans or animals, they draw blood tainted with a disease germ, which can then be spread to other people through further bites.

Mosquitoes actually have a very similar mechanism to fruit flies of a type of active tuning, which could have implications for deterring the spread of so many diseases. So, understanding how fruit flies and mosquitoes not only mate but also how they hear could have important considerations for human health.”

Daniel Eberl, Professor and Study Corresponding Author, University of Iowa

To record the sound of a male fruit fly species flapping its wings, the researchers employed tiny microphones. The female fruit fly's antennae pick up on the vibrations, or pulses, in the air caused by the beating of the wings, which indicate the presence of a male mate. The antenna of a female fruit fly functions similarly to the human ear in that it is a sensory organ that “hears” vibrations.

The fact that not all courtship songs are the same is intriguing.

I think a key point for us is that the songs that they sing are a little bit different in closely related species. The spacing between the pulses is distinct for each species. And that is why it is important because they want to mate with a mate from their own species. So, the song helps them give that recognition of the same species.”

Daniel Eberl, Professor and Study Corresponding Author, University of Iowa

It has been observed by biologists that female flies adjust their antennae to a frequency that is comparable to the range of sounds produced by males of the same species. They were unaware of the precise location and method of that fine-tuning.

The hearing in the well-known and extensively researched fruit fly species Drosophila melanogaster was investigated by the Iowa researchers. They specifically looked at the fly's Johnston's organ, which is found in the antenna and is where sound is detected. They discovered and investigated a potassium ion channel pathway in the Johnston's organ, which energizes the neurons responsible for the fly's hearing.

After more research, they discovered that a gene known as Shal acts as the ion channel's gatekeeper, controlling when external sounds or motions are translated into electrical signals that are subsequently transmitted between neurons. The fly's ability to hear seemed to depend on that series of events, which were controlled by the Shal gene.

To verify the Shal gene's function in a female fly's antenna tuning and, consequently, hearing, the researchers canceled it.

“Without the Shal gene, it loses that ability to tune. The female loses its ability to tune that antenna to that frequency. And so, you get this lower response in mating from that female,” said Eli Gregory, an undergraduate human physiology major from Cedar Rapids who carried out the gene-canceling experiments.

A similar technique is used by mosquitoes in their courtship rituals.

We could conceivably knock out that gene or that potassium channel and prevent mosquitoes from being able to mate as effectively as they do, which could mean fewer mosquitoes; therefore, fewer problems for human health.”

Daniel Eberl, Professor and Study Corresponding Author, University of Iowa

The study was published in the journal eNeuro.