‘Mosquitoes remember not only human smells, but also swats’

New York:  Your grandmother's insistence that you receive more bug bites because you are 'sweeter' may not be that far-fetched as a study claims that mosquitoes can rapidly learn and remember the smells of hosts. 

Researchers at Virginia Polytechnic Institute and State University in the US said dopamine is a key mediator of this process. Mosquitoes use this information and incorporate it with other stimuli to develop preferences for a particular vertebrate host species, and, within that population, certain individuals, they said. 

However, the study also proved that even if an individual is deemed delicious-smelling, a mosquito's preference can shift if that person's smell is associated with an unpleasant sensation. Hosts who swat at mosquitoes or perform other defensive behaviours may be abandoned, no matter how sweet they are, according to the study published in the journal Current Biology. 

The researchers said mosquitoes exhibit a trait known as aversive learning by training female aedes aegypti mosquitoes to associate odours (including human body odours) with unpleasant shocks and vibrations. Aedes aegypti mosquitoes are vectors for Zika fever, dengue fever, chikungunya, and yellow fever viruses, and can be found in tropical and subtropical regions throughout the world.

Twenty-four hours later, the same mosquitoes were assessed in a Y-maze olfactometer in which they had to fly upwind and choose between the once-preferred human body odour and a control odour. 

The mosquitoes avoided the human body odour, suggesting that they had been successfully trained. By taking a multidisciplinary approach and using cutting-edge techniques, including CRISPR gene editing and RNAi, the scientists were also able to identify that dopamine is a key mediator of aversive learning in mosquitoes.