Mosquito brains are wired to spot us

Summer is coming and with it the mosquitoes that ruin our evenings. Even our days now. The process by which they can find us so effectively to sting us has long remained a mystery. Today, thanks to the mobilization of different areas of expertise, researchers finally offer an answer.

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A mosquito bite, it’s annoying. It itches, usually. But in some parts of the world, it’s much worse than that. What scientists call Aedes aegyptian under consideration now the main vector of the dengue fevervirus Zikaby chikungunya and a little yellow fever† We understand why scientists are looking for solutions that can save us from its bite.

The problem is that this particular mosquito has also developed a tendency to bite almost exclusively humans. Does this mean that he can distinguish the smell of a human from that of another mammal? It looks like it. And after years of effort, Princeton University researchers (United States) think they have finally understood how, thanks to very high resolution images by brain mosquitoes.

It was not easy. Scientists from different backgrounds got involved. The researchers first had to design genetically modified mosquitoes whose brains light up when they are active. Two years of work. Then they had to make them smell human odors — recovered by taking care not to contaminate them with the odors from the fibers of our clothing — and animals — recovered with the greatest of precautions from hair in particular, taken here on rats, sheep, guinea pigs or even dogs – hoping to observe differences in response in said mosquitoes. Another two years of work to develop a system that effectively diffuses these scents. Still time to build an imaging system suitable for studying mosquito brains. But everything seems rewarded today.

An incredibly simple mechanism

To understand this, remember that mammals’ scents — including our own — are made up of dozens of different compounds. A complex mix. So for the . to distinguishhuman scent from that of animals, scientists believed that mosquitoes must have evolved a sophisticated mechanism. That’s why they wanted to dig into their brains.

And surprised! The mosquito actually uses a surprisingly simple mechanism to target its prey. Of the 60 nerve centers — scientists call them glomeruli — that mosquitoes have, only two are involved. The first acts as a launcher alert, signals nearby odors no matter which one. The second is the one responsible for confirming – or not – that it is a human scent.

Two is also the number of compounds in our scent that seem to interest mosquitoes. And researchers have identified them, too: decanal — with the formula CH₃(CH₂)₈CHO — and undecanal — with the formula C₁₀H₂₁CHO. They have already patented a mixture containing decanal, which they hope could lead to bait that draws mosquitoes to deadly traps or repellents that interrupt the signal.

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