Knowing how mosquitoes hear can help combat the spread of diseases

Diseases carried and transmitted by mosquitoes – including the Zika virus, malaria and yellow fever – are responsible for an estimated 725,000 deaths annually and they incapacitate a large proportion of the earth’s population.

Scientists at the University of Brighton have been studying mechanisms by which male mosquitoes use their ‘buzzing’ sound to detect females. The research could lead to the production of acoustic traps, better genetically-modified male mosquitoes and the disruption of mosquito mating, which, in turn, could significantly reduce their numbers.

Mosquitoes are well known for their annoying whine when they fly. The sound is produced by their wings which beat several hundreds of times per second. The male’s buzz is typically higher in pitch than that produced by the relatively larger females. Mosquitoes use this frequency difference to detect and communicate with possible mating partners. Mosquitoes are more sensitive to sound than any other insect due to the remarkable properties of their antennae and auditory organ at the base of each antenna.

Mosquito head and antennae

Dr Patrício Simões

The researchers, Dr Patrício Simões, PhD student Robert Ingham, and Professor Ian Russell, from the University of Brighton’s School of Applied Sciences, along with Professor Gabriella Gibson from the University of Greenwich, discovered that the male mosquitoes’ hearing organ is actually tuned to the frequency difference between its own flight-tone and a female’s flight-tone. The researchers’ work on this hearing mechanism, unique to the animal kingdom, is reported in the Journal of Experimental Biology.

Central to these findings, was the discovery and description of a stereotypical acoustic behaviour – a specific sound signature – which male mosquitoes produce when they detect female-like sounds. This never-before described and quantified behaviour is only observed in free-flying males. It enabled the researchers to ‘ask’ male mosquitoes what sounds characteristics are most attractive to males.

Researchers “unexpectedly and surprisingly” found a mismatch between the best tones that evoked the acoustic behaviour and the best tones detected by the hearing organ at the base of the antennae. This mismatch is solved by the hearing organ by detecting and amplifying the difference between the males’ own flight tone and that of a nearby female.

Dr Simões said: “Our findings reveal that the remarkable hearing capacities of mosquitoes are based not on harmonic detection, as is generally accepted and described in recent papers and text books, but on the detection of acoustic distortion-products produced by the interaction of the two sounds.

“This discovery gives a new significance for mosquito swarming because it implies that male mosquitoes have to fly in order to acoustically detect, locate and orientate towards flying females.”

Dr Simões said the full significance of this discover is still being investigated but it holds potential interest for creating new strategies to control mosquito populations, especially for disease-carrying mosquito species.