A key step in mosquito mating is auditory: Male mosquitoes detect the precise buzz of a female nearby, often in the midst of large swarms of other mosquitoes. A new study identifies a specific neurotransmitter chemical, octopamine, linked to mosquito hearing, suggesting that targeting it with insecticide could be a new potential avenue for mosquito management. Shown here is a female Anopheles gambiae mosquito, the species examined in the new study and a primary vector of malaria. (Photo by James D. Gathany, CDC Public Health Image Library)

Specific receptors in the antennae of mosquitoes have been revealed to modulate their hearing, according to a new study led by researchers at University College London and University of Oldenburg. The ability of male mosquitoes to hear female mosquitoes is a crucial requirement for their reproduction. As a result, the finding could help develop novel insecticides or mating disruptors to reduce mosquito populations and lessen the spread of mosquito-borne diseases like malaria, dengue, and yellow fever.

In the study, published in July in Nature Communications, the researchers focused on a signaling pathway involving a molecule called octopamine. They demonstrated that it is key for mosquito hearing and mating-partner detection and so is a potential new target for mosquito control.

Male mosquitoes acoustically detect the buzz generated by females within large swarms that form transiently at dusk. As these swarms are potentially noisy, mosquitoes have developed highly sophisticated antennae, or “ears,” to detect the faint flight tone of females amid hundreds of mosquitoes flying together.

However, the molecular mechanisms by which mosquito males “sharpen their ears” to respond to female flight tones during swarm time have been largely unknown. The researchers looked at the expression of genes in the mosquito ear and found that an octopamine receptor specifically peaks in the male mosquito ear when mosquitoes swarm.

The study found that octopamine affects mosquito hearing on multiple levels. It modulates the frequency tuning and stiffness of the sound receiver in the male ear and also controls other mechanical changes to boost the detection of the female.

The researchers demonstrated that this system in the mosquito ear can be targeted by insecticides. Mosquito mating is a bottleneck for mosquito survival, so identifying new targets to disrupt it is key to controlling disease-transmitting mosquito populations.

“Octopamine receptors are of particular interest as they are highly suitable for insecticide development. We plan to use these findings to develop novel molecules to develop mating disruptors for malaria mosquitoes,” says Marta Andrés, Ph.D., of the University College London Ear Institute, co-lead author of the study. “Because mosquito hearing is required for mosquito mating, it can be targeted to disrupt mosquito reproduction. And increased knowledge of mosquito auditory neurosciences could lead to the development of mosquito mating disruptors for mosquito control.”

Co-lead author Joerg Albert, Ph.D., of the UCL Ear Institute and University of Oldenburg, adds, “The molecular and mechanistic complexity of mosquito hearing is truly remarkable. With the identification of an octopamine pathway, we are just beginning to scratch the outer surface of the tip of an iceberg. Future studies will without doubt deliver deeper insights into how mosquito hearing works and also provide us with novel opportunities to control mosquito populations and reduce human disease.”

Adapted from a press release published by the University College London via EurekAlert, August 11, 2023