A bit like Pavlov's dogs, mosquitoes appear to avoid the smells that they associate with having to dodge blows.
In a new study published in their journal Current Biology on January 25, researchers showed that mosquitoes can learn and remember the smells of their hosts, allowing these pesky pests to develop preference for certain individuals. But there is evidence that they can change their preferences, which led scientists to wonder what caused these shifts.
"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", Jeffrey Riffell at the University of Washington, Seattle, said in a statement. As a result, mosquitoes became less able to process and learn from odor information.
In the first experiment, the researchers paired a particular odor with a mechanical shock (effectively mimicking what a swat would feel like using a vortex mixer).
Learning in many animals, from honey bees to humans, depends on dopamine in the brain.
Researchers determined this by exposing mosquitoes to a choice between a sleeve that either had a human odor or did not.
To test this, the team trained the mosquitoes by combining the smell of a particular person or animal species with a mechanical shock produced by a vortexer machine.
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. "For example, we could target mosquitoes' ability to learn and either impair it or exploit it to our advantage".
A mosquito flies on the end of a tether during an experiment to study responses to a swat-like shock.
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.
The researchers also glued mosquitoes to a custom, 3D-printed miniature "arena" in which the insects could fly in place, while researchers recorded the activity of neurons in the olfactory center of their brains.
Of course, these findings could offer much more than an insight into how to avoid the annoyance of a few itchy bites; they might also be significant in controlling the spread of mosquito-borne disease.
The study was published Thursday in the journal.
"Now that we have a better understanding of what the mosquitoes are capable of", she said, "we need to investigate how to apply this knowledge to refine our control strategies and fight more efficiently against the disease that these mosquitoes transmit".
They attributed this ability to dopamine, a neurotransmitter that sends signals to other parts of our brain.
"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". In addition to Vinauger, Lahondere and Riffel, the authors include Gabriella Wolff, Lauren Locke, Jessica Liaw and Jay Parrish from UW, plus UC-Riverside's Omar Akbari and Caltech's Michael Dickinson.