Important Lessons from Mosquitoes in a 3D Printed Arena

Smell is a powerful memory trigger. If you smell cookies, it may remind you of your grandmother’s house, while the scent of sunscreen may bring back memories of a favorite vacation. And if mosquitoes smell you, they may be reminded of being swatted – and fly in the other direction.

In a paper entitled “Modulation of Host Learning in Aedes aegypti Mosquitoes,” which you can access here, a group of researchers discuss how mosquitoes as a whole can learn to associate a particular scent with being swatted. So if you swat mosquitoes every time they land on you, they may actually begin to avoid you.

“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,” said senior author Jeff Riffell, Professor of Biology at the University of Washington. “Moreover, mosquitoes remember the trained odors for days.”

Jeff Riffell

Mosquitoes already have their preferences in whom they bite – you may know people who can barely sit outside on a summer night without getting devoured, while others seem to be able to sit within clouds of mosquitoes without a single bite. It’s infuriating to the people who are getting bitten, but fascinating to researchers, who have also determined that mosquitoes change their biting behavior seasonally, choosing to feed on birds in the summer and mammals at other times of the year. For this particular study, the researchers wanted to find out how learning might influence mosquitoes’ biting habits.

They first trained the mosquitoes by pairing a particular animal with a mechanical shock that simulated a swat, using a vortex mixer to simulate the vibrations and accelerations a mosquito might experience during a swat. The mosquitoes quickly learned the association between the shock and the smell of that particular animal, although no matter what the consequences, they never avoided chickens – apparently mosquitoes love chicken as much as humans do.

They also discovered that it all comes down to dopamine. Genetically modified mosquitoes lacking dopamine receptors in their tiny brains did not have the ability to learn as the natural mosquitoes did. The researchers then 3D printed a miniature arena into which they glued the mosquitoes, allowing them to fly in place while the researchers recorded the activity of neurons in the olfactory centers of their brains. Without dopamine, the experiments showed, those neurons were less likely to fire. That meant the mosquitoes were less able to process and learn from odors.

In addition to encouraging people to swat mosquitoes as much as possible, the research may prove valuable in large-scale mosquito control and prevention of transmission of mosquito-borne diseases.

“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,” said Riffell. “This could lead to more effective tools for mosquito control.”

Dopamine staining in the brain of a mosquito

Now that they have a better understanding of why mosquitoes may avoid certain people, the researchers are investigating the insects’ ability to develop “favorites.”

“In both cases, we think dopamine is a critical component,” said Riffell.

Authors of the paper include Clément Vinauger, Chloé Lahondère, Gabriella H. Wolff, Lauren T. Locke, Jessica E. Liaw, Jay Z. Parrish, Omar S. Akbari, Michael H. Dickinson, and Jeffrey A. Riffell.

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