Genetic studies have revealed that when male mosquitoes lose their hearing, they also lose their sex lives. The surprising discovery could lead to new ways to reduce mosquito populations and the diseases they spread.
There’s nothing more annoying to us humans than the high-pitched whine of a mosquito buzzing around your bedroom while you’re trying to sleep on a hot night. But to other mosquitoes, that’s the hottest sound imaginable.
Scientists have long known that hearing is the main sense used in mosquito mating. Females beat their wings at frequencies of around 500 Hz, and males hear this and respond by taking flight, modulating their own wingbeats at around 800 Hz. A few seconds of midair copulation, and the courtship is done.
“On summer evenings, we often see swarms of mosquitoes gathered by the water or under streetlights,” said Yijin Wang, co-lead author of the study. “These gatherings are essentially mass mating events.”
In most species, the act of mating is a multisensory experience, so for the new study, researchers at UC Santa Barbara investigated what would happen if they took hearing out of the equation for mosquitoes. Using the CRISPR-Cas9 gene-editing system, the team knocked out a gene called trpVa in the insects.
These mutant mosquitoes showed no reaction to sound whatsoever, and no electrical activity was detected in the neurons known to be associated with hearing. That confirmed that the gene edits had worked.
Next, the researchers placed the deaf mosquitoes in a mixed population, and watched what happened. Deaf females had a harder time than usual attracting mates, but still managed to get the job done. Deaf males, however, didn’t respond at all to the waiting ladies, leaving all the fun to those with unimpaired hearing. That suggests that this is the sole sense males use to find mates.
“I think the reason why our major finding is so shocking is because, in most organisms, mating behavior is dependent on a combination of several sensory cues,” said Emma Duge, co-lead author of the study. “The fact that taking away a single sense can completely abolish mating is fascinating.”
The strange discovery won’t be used for mosquito couples counseling. Quite the opposite, in fact – the researchers believe it could be used against them for population control. Already, male mosquitoes have been genetically engineered to be sterile, then released in various regions in recent years. The idea is that sterile males will still try to mate, but their partner's eggs won’t hatch. And conveniently, after females mate once, they don’t usually do so again, so the population comes down quickly.
The problem there is that the sterile males have to outcompete natural, virile males for female attention, so populations usually bounce back after a while. But what if the sterile bugs had a female-finding advantage over wild ones?
Rather than knocking out the trpVa gene and making mosquitoes deaf, the team suggests that it could instead be made overactive in these sterile mosquitoes. If they’re more sensitive to the wing-beating of receptive females, they could pair off before all the natural mosquitoes realize what’s going on.
If so, we might have a new way to control the spread of diseases like malaria, Zika, and dengue fever.
The research was published in the journal PNAS.
Source: UCSB