Last updated January 26, 2018 at 12:43 pm
One of the reasons mosquitoes are so annoying could be that they are actually quite smart. The up side is that it may help us work out how to keep them away.
The visual arena where researchers tested trained mosquito responses to various odours. Credit: Kiley Riffell
The humble mossie can learn to associate a particular odour with an unpleasant mechanical shock akin to being swatted and will avoid that scent the next time. And it is quite a strong response.
“Once mosquitoes learned odours in an aversive manner, those odours caused aversive responses on the same order as responses to DEET, which is one of the most effective mosquito repellents,” says Associate Professor Jeffrey Riffell from University of Washington, Seattle.
Mosquitoes don’t bite at random
“Moreover, mosquitoes remember the trained odours for days.”
We all know that mosquitoes don’t bite at random; they show obvious preferences for some people over others and will even alternate hosts seasonally.
Riffell and his colleagues wanted to find out more about how learning might influence these biting preferences.
As a first step, they trained mosquitoes by pairing the odour of a particular person or animal species (a rat versus a chicken) with a mechanical shock.
A vortexer machine was used to simulate the vibrations and accelerations a mosquito might experience when a person tries to swat them.
The insects quickly learned the association between the odour and the shock and used that information in deciding which direction to fly.
Mosquito learning relies on dopamine
Interestingly, they couldn’t learn to avoid the smell of a chicken.
Learning in many animals, from honeybees to humans, depends on dopamine in the brain. Additional study showed that dopamine is also essential in mosquito learning.
Related: The hidden heroes tackling mosquitoes
Genetically modified mosquitoes lacking dopamine receptors lost the ability to learn.
The researchers also glued mosquitoes to a custom 3D-printed holder that allowed them to fly in place while the activity of neurons in the olfactory centre of their brains was recorded.
This showed that without dopamine those neurons were less likely to fire. As a result, mosquitoes became less able to process and learn from odour information.
How do mosquitoes make decisions?
The findings may have implications for mosquito control and, perhaps more importantly, the transmission of mosquito-borne diseases
“By understanding how mosquitoes are making decisions on whom to bite, and how learning influences those behaviours, we can better understand the genes and neuronal bases of the behaviours,” Riffell says. “This could lead to more effective tools for mosquito control.”
The research team is now exploring mosquitoes’ ability to learn and remember favoured hosts.
“In both cases, we think dopamine is a critical component,” Riffell says.
The paper recently published by Current Biology.
