PARIS, August 23 (Benin News) –
Researchers have found that mosquitoes have evolved redundant safety devices in their olfactory systems that allow them to always smell humans, according to the journal ‘Cell’.
When female mosquitoes seek out a human to bite, they smell a unique cocktail of human-specific body odors, which stimulate receptors in the mosquito antennae. Scientists have tried to eliminate these receptors to make humans undetectable by mosquitoes.
However, even following eliminating a whole family of odor-sensitive receptors from the mosquito genome, they still find a way to bite us.
“Mosquitoes break all of our favorite rules regarding animal odor,” agrees Margo Herre, a scientist at Rockefeller University in the United States and one of the lead authors of the paper.
In most animals, an olfactory neuron is only responsible for detecting a single type of smell. “If you’re a human and you lose a single odorant receptor, all of the neurons that express that receptor will lose the ability to smell that odor,” says Leslie Vosshall of the Howard Hughes Medical Institute, a professor at Rockefeller University and lead author of the item. But she and her colleagues found that this is not the case in mosquitoes.
“You have to work harder to get rid of mosquitoes, because getting rid of just one receptor has no effect,” she warns. Any future attempt to control mosquitoes using repellents or anything else must take into account the unwavering attraction they hold for us.
“This project really got off to an unexpected start when we studied how human scent was encoded in the mosquito brain,” adds Meg Younger, a Boston University professor and one of the paper’s lead authors.
They found that neurons stimulated by the human odor 1-octen-3-ol are also stimulated by amines, another type of chemical that mosquitoes use to seek out humans. This is unusual, because according to all existing rules of animal olfaction, neurons encode odors with narrow specificity, suggesting that 1-octen-3-ol neurons should not detect amines.
“Surprisingly, the neurons capable of detecting humans through 1-octen-3-ol and amine receptors were not separate populations,” Younger notes. This may allow all human-related odors to activate “the part of the mosquito’s brain that senses humans”, even if some of the receptors are lost, providing a fail-safe mechanism.
The team also used single-nucleus RNA sequencing to see what other receptors individual mosquito olfactory neurons express. “This result gave us an overview of the frequency of receptor co-expression in mosquitoes,” says Olivia Goldman, another lead author of the paper.
Vosshall thinks other insects might have a similar mechanism. Christopher Potter’s research group at Johns Hopkins University recently reported that fruit flies exhibit similar co-expression of receptors in their neurons. “This might be a general strategy for insects that rely heavily on their sense of smell,” says Vosshall.
In the future, Meg Younger’s group plans to discover the functional significance of the co-expression of different types of olfactory receptors.
