And, yes, mosquitoes have preferences when it comes to meals.
Researchers determined this by exposing mosquitoes to a choice between a sleeve that either had a human odor or did not.
After the training period, the mosquitoes were put in chambers where they could choose which scent to head toward. For the mechanical shock, they used a vortex mixer to simulate the vibrations and accelerations a mosquito might experience when a person tried to swat them.
The full statement from the university follows below. Vinauger and Lahondere are former UW researchers who are now at Virginia Tech.
The study, published in Current Biology, was intricately created to gauge the learning abilities of the mosquito species, Aedes aegypti.
Have you ever wondered why some people manage to avoid falling prey to mosquitoes while others end up totally covered in bites?
A tethered, flying Aedes aegypti mosquito. The mosquitoes avoided the human body odor, suggesting that they had been successfully trained.
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. That didn't hold up once the insects experienced the mechanical shock that was associated with the smell of a certain human, the study found.
Learning in many animals, from honey bees to humans, depends on dopamine in the brain.
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"Unfortunately, there is no way of knowing exactly what attracts a mosquito to a particular human - individuals are made up of unique molecular cocktails that include combinations of more than 400 chemicals", said Lahondère.
They chose the control odor up to 24 hours later, indicating they'd learned to avoid signs of danger.
"Understanding these mechanisms of mosquito learning and preferences may provide new tools for mosquito control", said Vinauger. Indeed, genetically modified mosquitoes without dopamine receptors were unable to make the same associations between the smell of humans and the mechanical shock.
The abstract from the paper follows below.
Researchers already knew that mosquitoes don't decide whom to bite at random.
It is fairly well established that various mosquito species not only go for certain sorts of animal at certain times of the year, but will also tend to feed on certain individuals. Here, we show that olfactory learning may contribute to Aedes aegypti mosquito biting preferences and host shifts. 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.
The experiments showed that without dopamine, those neurons were less likely to fire, suggesting that mosquitoes became less able to process and learn from odour information. Additional experiments by Riffell and his team showed that dopamine is also essential in mosquito learning.