News

Mosquito’s buzz could be its downfall

Published 14 March 2013

Scientists at the University of Brighton have won a £194,000 grant to study the mosquito's buzzing sound in a bid to hinder the spread of malaria which kills up to 3,000 people – mainly children – every day.

Professor Ian Russell, an auditory neuroscientist, will be co-leading research with Dr Gabriella Gibson, an expert in mosquito sensory behaviour, into the mechanisms by which male and female mosquitoes use their buzzing to recognise and perhaps attract each other. The aim is to understand the significance of mosquito love duets and how they might be used to control the breeding behaviour of mosquitos and the spread of malaria.

Professor Russell said: "It has been known for some time that dulcet flight tones, the familiar whine people hear when mosquitoes fly close, are music to the male mosquito's ear, guiding him through sound alone to rendezvous with a potential mate."

The male's hearing organ, found at the base of its antenna, is the most sensitive of all known invertebrate 'ears' and Professor Russell, who heads the Hearing Research Group in the University of Brighton's School of Pharmacy and Biomolecular Sciences, has discovered that the female’s hearing comes a close second.

A closer look at the head of a male mosquito. The plumose antennae are inserted at their base into the doughnut shaped pedicel; the location of the mosquito’s hearing organ (Johnson’s organ). There are almost as many sensory cells crammed into the tiny Johnson’s organ as in the mammalian cochlea.
Image © Dr Gareth Jones, University of Brighton

He said: "We have shown that as soon as a male-female pair of flying mosquitoes can hear each other's flight tones, they enter into a harmonising duet, each adjusting the frequency of their own wing-beats to match, or nearly match, a harmonic of their flight tone with a harmonic of the other. What starts as a discordant cacophony resolves quickly toward harmony.

"That mosquitoes harmonise is remarkable and provides them with a means of sex recognition and possibly species recognition. But how they harmonise is, however, not fully understood, and is the subject of our research."

Professor Russell said his team's preliminary findings suggest mosquitoes are unique in the animal kingdom in that they have the ability to detect and exploit acoustic distortions. These are generated through the mixing of two tones in their ears so that they can hear each other. Distortion products are tones, generated in the ear, at frequencies that are not present in the two stimulus tones. An example is the difference tone which is used by the mosquitoes to measure the frequency difference between their flight tones.

He said: "We aim to determine the functional significance of acoustic distortion products, especially for the detection of males by female mosquitoes and investigate whether distortion products hold the key to species-specific recognition during harmonising interactions. This knowledge will help to elucidate how the most notorious malarial species, Anopheles gambiae s.s., has been able to diversify so quickly into a range of molecular forms, adapting to new human habitats as quickly as they do."

Mosquitoes are the most common carriers of malaria and they spread the disease when females bite to draw blood which is used to nurture their eggs. According to the World Health Organisation, there were 219 million documented cases of malaria in 2010 and upwards of 1.2 million people died from the disease.

A new BBC film on the devastating effects of malaria has been produced for Comic Relief's Red Nose Day on 15 March. Mary & Martha, written by Richard Curtis, tells the story of two women whose sons died from malaria in South Africa and then campaign for more funds for prevention and relieving suffering. It stars Oscar-winning actress Hilary Swank and Bafta winner Brenda Blethyn.

Professor Russell said: "Malaria is one of the world's biggest killers and by learning more about mating sounds and habits of mosquitoes we can learn ways of controlling their breeding habits and, in the long term, reduce the spread of malaria."

The £194,000 grant has been made by Leverhulme Trust which makes awards for the support of research and education. It was started by Victorian businessman William Lever who founded Lever Brothers.

Professor Russell is leading the two-year research project with Dr Gibson from the Natural Resources Institute at the University of Greenwich. Also involved is Rob Ingham, insect neurophysiologist from the University of Brighton, and a University of Brighton postdoctoral research fellow, to be appointed.