Swatting Mosquitoes Teaches Them To Avoid You

Posted January 28, 2018

With humans and rats, mosquitoes introduced to the mechanical shock were more likely to stay away, according to the study, suggesting the insects remembered the unpleasant experience when deciding where to find their next meal.

"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 study researcher Jeff Riffell, from UW.

Mosquitoes can distinguish the scent of hosts that exhibit defensive behaviors such as swatting.

A bit like Pavlov's dogs, mosquitoes appear to avoid the smells that they associate with having to dodge blows.

Learning in many animals, from honey bees to humans, depends on dopamine in the brain.

A mosquito flies on the end of a tether during an experiment to study responses to a swat-like shock.

Researchers already knew that mosquitoes don't decide whom to bite at random. Mosquitoes will also blood feed from other hosts when their preferred is no longer abundant, but the mechanisms mediating these shifts between hosts, and preferences for certain individuals within a host species, remain unclear.

The mosquitoes were again tested 24 hours later in a custom 3D-printed holder, allowing them to still fly in place while the researchers were recording the activity of neurons in the olfactory centre of their brain.

Clement Vinauger and Chloe Lahondere are the lead authors of the study, titled "Modulation of Host Learning in Aedes Aegypti Mosquitoes". Not only do these results provide direct experimental evidence that olfactory learning in mosquitoes can play an epidemiological role, but collectively, they also provide neuroanatomical and functional demonstration of the role of dopamine in mediating this learning-induced plasticity, for the first time in a disease vector insect. However, they did not learn to veer away from chickens, and researchers believe it's because the insects learned to avoid specific scents that are in mammals, but apparently not in birds. "For example, we could target mosquitoes' ability to learn and either impair it or exploit it to our advantage".

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.

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

A mosquito brain, highlighting dopamine in areas associated with sense of smell.

A new study published in the journal Current Biology revealed that, despite their small size, mosquitoes might be smarter than we give them credit for.

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. The project is supported by the National Institutes of Health, the Air Force Office of Sponsored Research, the National Science Foundation, and more.