Good news, especially for residents of the tropics where these mosquitoes carry dangerous pathogens.
Spring has finally come, to delight lovers of strolls and picnics in the great outdoors. But like every year, it also signals the return of a few unwanted people we can do without, starting with those pesky mosquitoes. And American researchers have just identified a mechanism that could explain their tendency to destroy our barbecues.
team ofPrinceton University Thus he was particularly interested in a species called Egyptian temples. It is a small beast that is a particular problem because it can carry a whole mixture of pathogens such as malariaheart virus, ZikaThe dengue fever or the yellow fever. And it turns out that within a few decades, these species have evolved to target almost exclusively one species: we !
From the point of view of biologists, this is an interesting transition. This already indicates that in order to survive depending on one species, they had to evolve Incredibly accurate targeting strategies Researchers have tried to understand it. Their ultimate goal: to pinpoint the exact mechanisms that allow mosquitoes to identify humans.
“We’ve more or less delved into the brains of mosquitoes to ask them: What do they smell? What activates your neurons, and what lights up differently in your brain when you smell a human being?? ,” summarizes Carolyn McBride, Professor of Evolutionary Biology, Ecology and Neurosciences at Princeton University.
Hunting for treasure by smell
To achieve this, researchers have developed a highly optical approach. they produced genetically modified strain mosquito who Neural structures selectively light up when activated. They then put these mosquitoes in contact with animal scents, including human scents, to try to see this mechanism more clearly using an imaging system designed specifically for the occasion.
The problem is that there are as many human smells as humans do. And for good reason: This scent comes from a very complex blend of dozens of organic compounds. However, none of them matter to mosquitoes alone. So the researchers concluded that mosquitoes responded with a very special combination. But how do you find it?
Without any initial leads, they had no choice but to proceed experimentally. They began to collect scents from rats, guinea pigs, quails, sheep and dogs. But for humans, it was more complicated; Having a “pure” human scent is less obvious than it sounds. In fact, the majority of us regularly use scented hygiene products. Even clothes can change this smell dramatically.
So some volunteers had to blow themselves away. “We asked them not to shower for several days, undress, and then lie down in a large Teflon bag.‘,” laughs Jessica Tsung, a member of the research team. Then they had to develop a system that would allow them to extract and isolate these odors.
Surprisingly simple process
The compounds that are likely to cause mosquitoes to react is still being accurately identified. So the researchers spent several months exposing mosquitoes to the many combinations of the different compounds that were identified during the combination. Then they reviewed the results to determine the most effective markers.
The researchers expected to discover a highly sophisticated tracking system. But the process they identified surprised them with its simplicity, as it appears to be based on only two specific organic compounds:illegal and the decimalwhich is an aldehyde also found in buckwheat and coriander essential oils … or the famous olive essential oil Chanel No. 5! With good relations…
Another point that surprised the researchers is the reaction that these compounds cause in the nervous system. The mosquito “brain” is a structure made up of about 60 structures called glomeruli. The researchers expected that majority From these glomeruli are involved in the hunting of humans, since this is a vital activity of these mosquitoes; In fact there is only… who are they.
“When I first saw this brain activity, I couldn’t believe itZhilei Zhao, a doctoral student who played a key role in this study, explains.There were only two glomeruli involved, which went against all our expectations. It’s amazing that this system is so simple‘ she asks.
The door is open to highly tangible solutions
This discovery is likely to have serious consequences, some of which are very tangible. Because this work was done on mosquitoes that are known to be vectors of very problematic diseases. Now that researchers have found the chemical compounds that attract them the most, it opens the door to a whole host of countermeasures to combat the public health epidemic. It is enough, for example, to use it for To seduce into a deadly trap.
We can also imagine Repellents that specifically block this signalThus preventing mosquitoes from detecting a human by smell. This is a more interesting solution. Because even if they are painful, mosquitoes remain a major player in many ecosystems.
For example, many birds or spiders depend directly on mosquitoes because they are an important part of their diet. Ideally, it is therefore better to try to drive them away than to eliminate them, as this may signal a start A catastrophic chain reaction for some environmental outlets.
Ultimately, it would also be interesting to extend this work to other species. This will initially allow us to find out if the mechanism is intended for these specialized fishermen, or, on the contrary, it is Universal in all types of mosquitoes. If necessary, it will be possible to develop a simple, harmless and ecosystem-friendly solution to avoid serving as a travel buffet. Good news for fishing and picnic enthusiasts… But Especially for all residents of the tropics whose life can be completely changed due to a simple mosquito bite.
Study text available ici.