A team of researchers from the Group of Neural Circuit at the Graduate School of Science at Nagoya University in central Japan have developed a new method that could help control mosquito populations. The annoying buzzing mosquitoes make in flight inspired this technique.
Mosquitoes aren’t just a nuisance for people sitting outside on hot summer evenings. They also spread deadly diseases that kill thousands of people each year, including dengue fever, malaria and the Zika virus. Therefore, it is vital to reduce mosquito populations around the world. Unfortunately, commonly used insecticides have become less effective over time because mosquitoes have developed resistance. They also have a negative impact on the environment. Therefore, alternative methods are needed to control mosquitoes.
A promising method for controlling mosquitoes takes advantage of perhaps their most annoying characteristic – their high-pitched buzzing. Females create this sound when flying in search of blood sources. Male mosquitoes specifically listen for this characteristic high-pitched noise. Shaped like antennae, the ears of male mosquitoes vibrate at the same frequency as the wings of female mosquitoes. When a female flies, the ears of the male pick up this frequency and resonate, sending a signal to his brain that helps him identify a potential mate.
A team of researchers from Nagoya University, led by Dr Matthew Su and Professor Azusa Kamikouchi, tested whether they could control mosquito mating behavior by altering how often male mosquitoes listen. By making the ears of male mosquitoes “detune” they sought to influence their mating behavior. “Many laboratories around the world are trying to prevent mosquitoes from biting humans,” explained Dr Su. “In our lab, however, we take a slightly different approach. What if these females that bite humans were never born? Rather than preventing females from biting humans, let’s make sure there are fewer mosquitoes to begin with.”
To test their theory of a sound method of mating control for mosquito populations, the team first identified the involvement of the major neurotransmitter serotonin in the insect’s auditory system. Serotonin plays an important role in the nervous system and brain of various animals, influencing a wide range of behaviors.
After demonstrating the presence of serotonin in the mosquito’s auditory system, the team’s next step was to manipulate serotonin levels. To do this, they used a method called “laser doppler vibrometry”. This involves the use of a laser as a highly sensitive measurement tool to detect changes in the nanoscale vibrations of mosquito ears after exposure to serotonin-related compounds. Researchers found that after feeding mosquitoes a serotonin-inhibiting compound, the vibration frequency of male ears decreased. When they gave the mosquitoes glucose mixed with a compound that inhibits serotonin, the range of frequencies to which the mosquitoes responded and their response itself was reduced.
The next step in developing a possible hearing-based “birth control” will be to identify the exact receptors responsible for tuning mosquito ears. This could allow researchers to administer compounds targeted to disrupt mating behavior. “My dream is to find a very precise target, maybe even a mosquito-specific target,” Dr Su said. “Then we could leave the other species untouched.”
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Material provided by Nagoya University. Note: Content may be edited for style and length.