Most of us surely don’t think of mosquitoes as being especially adept at learning. But that may not be the case. In a paper published on January 25 in Current Biology, University of Washington researchers report that they can, in fact, learn to associate a particular odor with an unpleasant mechanical shock akin to being swatted. As a result, they’ll avoid that scent the next time. Senior author Jeff Riffell, a UW professor of biology says:
“Once mosquitoes learned odors in an aversive manner, those odors caused aversive responses on the same order as responses to DEET, which is one of the most effective mosquito repellents; moreover, mosquitoes remember the trained odors for days.”
Researchers already knew that mosquitoes don’t decide whom to bite at random. They show obvious preferences for some people over others. They are also known to alternate hosts seasonally, feeding on birds in the summer and mammals and birds during other parts of the year, for instance. Riffell and his colleagues wanted to find out more about how learning might influence their biting preferences.
Using mechanical shocks to train mosquitoes
As a first step, they trained mosquitoes by pairing the odor of a particular person or animal species — a rat versus a chicken, for example — with a mechanical shock. For the mechanical shock, they used a vortex mixer 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 host odor and the mechanical shock, and they used that information in deciding which direction to fly — though interestingly, the mosquitoes could never learn to avoid the smell of a chicken.
Learning in many animals, from honeybees to humans, depends on dopamine in the brain. Additional experiments by Riffell and his team showed that dopamine also is essential in mosquito learning. Genetically modified mosquitoes lacking dopamine receptors lost the ability to learn.
Dopamine staining in the brain of an Aedes aegypti mosquito. (Image: Gabriella Wolff, Research Associate via University of Washington)
The researchers also glued mosquitoes to a custom, 3-D-printed miniature “arena” in which the insects could fly in place, while researchers recorded the activity of neurons in the olfactory centers of their brains. Those experiments showed that without dopamine, those neurons were less likely to fire. As a result, they became less able to process and learn from odor information.
These findings may have important implications for mosquito control and the transmission of mosquito-borne diseases, according to the researchers. Said Riffell:
“By understanding how mosquitoes are making decisions on whom to bite, and how learning influences those behaviors, we can better understand the genes and neuronal bases of the behaviors. This could lead to more effective tools for mosquito control.”
With this new understanding of how mosquitoes learn to avoid certain hosts, the researchers say they are now exploring mosquitoes’ ability to learn and remember favored hosts.
“In both cases, we think dopamine is a critical component,” said Riffell.
Watch this video about how mosquitoes may learn to avoid your scent:
Article provided by the University of Chicago. [Note: Materials may be edited for content and length.]
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