New study about how mosquitoes mate may boost war on malaria

Researchers uncover details about mating behaviour that could be key to disease control

A high-pitched buzz of a mosquito is not just an irritating sound — it’s also a signal of potential danger.

Female mosquitoes, the blood-feeders that transmit malaria, often draw human attention when they buzz close. Well, for male mosquitoes, this buzzing sound signals something entirely different, the cue to find a mate.

Many mosquito species have relatively poor vision. But in a new study, researchers have uncovered details about mosquito mating behaviour that could be key to improving malaria control strategies.

The study found that male mosquitoes, which have relatively poor vision, rely primarily on auditory cues, particularly the sound of female wingbeats, to locate potential mates.

This sound activates their visual systems, enabling them to navigate through crowded swarms to pinpoint females for mating.

Most Anopheles species gather in large swarms during sunset, with the majority being males and only a few females present. To the human eye, these swarms seem chaotic, as mosquitoes of both sexes dart past one another at high speeds.

Male mosquitoes must rely on their sensory abilities to navigate through the swarm, avoiding collisions while seeking out the elusive females for mating.

“We have discovered this incredibly strong association in male mosquitoes when they are seeking out a mate. They hear the sound of wingbeats at a specific frequency — the kind that females make — and that stimulus engages the visual system,” said lead author Saumya Gupta, a UW postdoctoral researcher in biology.

“It shows the complex interplay at work between different mosquito sensory systems.” Scientists in the research, led by the University of Washington, contained in a press release from the university and published in the Current Biology issue, who simulated these swarm-like scenes, now believe that the strong connection between male mosquitoes hearing the female-like buzz and moving toward an object in their field of vision could pave the way for new mosquito control methods, in the form of specialised traps targeting Anopheles mosquitoes, the primary carriers of malaria, by exploiting their attraction to specific sounds.

“This sound is so attractive to males that it causes them to steer toward what they think might be the source, be it an actual female or, perhaps, a mosquito trap,” said senior author Jeffrey Riffell, a UW professor of biology.

Scientists who included the Health Sciences Research Institute in Burkina Faso, Wageningen University in the Netherlands, and the University of Montpellier in France — tested the flight behavior of individual male mosquitoes, they built a miniature arena that uses a curved, pixelated screen to mimic the visual chaos of a swarm— essentially a mosquito flight simulator.

In it, the mosquito test subject, which is tethered and cannot freely move, can still see, smell and hear, and also beat its wings as if it is in flight.

In arena tests with dozens of male Anopheles coluzzii mosquitoes, the researchers discovered that males responded differently to an object in their field of vision based on what sound the researchers broadcast into the arena.

If they played to a tone at 450 hertz — the frequency at which female mosquito wings beat in these swarms — males steered toward the object.

But males did not try to turn toward the object if the researchers played a tone at 700 hertz, which is closer to the frequency at which their fellow males beat their wings.

The mosquito’s perceived distance to the object also mattered. If the simulated object appeared more than three body lengths away, he would not turn toward it, even in the presence of female-like flight tones.

“The resolving power of the mosquito eye is about 1,000-fold less than the resolving power of the human eye,” said Riffell. “Mosquitoes tend to use vision for more passive behaviors, like avoiding other objects and controlling their position.”

Arena experiments showed that male mosquitoes adjust their wingbeat patterns when responding to objects, even without hearing female flight tones. These subtle changes likely help them avoid collisions with other males.

“We believe our results indicate that males use close-range visual cues for collision avoidance within swarms,” said Gupta. “However, hearing female flight tones appears to dramatically alter their behavior, suggesting the importance of integrating sound and visual information.”

This research may demonstrate a new method for mosquito control by targeting how mosquitoes integrate auditory and visual cues.

The males’ strong and consistent attraction to visual cues when they hear the female buzz may be a vulnerability that researchers can utilize while designing the next generation of mosquito traps —particularly traps for the Anopheles species, which are a major spreader of malaria pathogens.

“Mosquito swarms are a popular target for mosquito control efforts, because it really leads to a strong reduction in biting overall,” said Riffell.

“But today’s measures, like insecticides, are increasingly less effective as mosquitoes evolve resistance. We need new approaches, like lures or traps, which will draw in mosquitoes with high fidelity.”

This story appeared on TheEastAfrican.