Swatting at a pesky mosquito, scientists now say, might be a pretty good method of defence after all. Even if you don’t actually hit the critter.
According to a study published in the scientific journal Current Biology on Jan 25, 2018, it turns out that a mosquito possibly remembers who it was that tried to swat it. It associates the scent of the human with the bad experience – and so, stays away from the person if at all possible.
According to a team of researchers led by biologist Jeffrey Riffell of the University of Washington in Seattle, United States, mosquitoes do not randomly bite their victims, but rather search out certain types.
This means that the Californian species Culex tarsalis, which is closely related to the common Culex pipiens, chiefly goes after birds in the summer. In winter, it will additionally seek out mammals.
In laboratory experiments with the female Aedes aegypti mosquito, the researchers described how they combined odours, including human body odours, with unpleasant experiences of shocks and vibrations.
Some 24 hours later, the same mosquitoes were studied in a so-called Y-maze olfactometer, flying upwind and having to choose which direction to go – the choice being between the previously-preferred human body odour and a control odour.
The mosquitoes avoided the human odour, an indication that they had remembered the unpleasant experience from the day before.
Riffell said, “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. Moreover, mosquitoes remember the trained odours for days.
“By understanding how mosquitoes are making decisions on whom to bite and how learning influences those behaviours, we can better understand the genes and neuronal bases of the behaviours. This could lead to more effective tools for mosquito control.”
Similar to the case with humans, the messenger substance dopamine plays an important role in the learning process. Those mosquitoes that, due to a genetic change, could not produce dopamine, had a much harder time learning the odours.
“Understanding these mechanisms of mosquito learning and preferences may provide new tools for mosquito control,” said Clément Vinauger, assistant professor at Virginia Tech University and study co-author. “For example, we could target mosquitoes’ ability to learn, and either impair it or exploit it to our advantage.”
The scientists caution that resolving the man-versus-mosquito battle is far from over.
“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 co-author Chloé Lahondère. “However, we now know that mosquitoes are able to learn odours emitted by their host and avoid those that were more defensive.” – dpa