There’s a ‘shocking and weird’ reason mosquitoes always seem to find us, study finds: ScienceAlert

The relentless precision with which some mosquito species hunt humans may result from their oddly wired olfactory systems, which have a built-in safeguard for detecting human scents.

Mosquitoes can detect CO₂ Where sweat emanating from humans using unique chemoreceptors in their antennae and the maxillary palp, an articulated sensory appendage of insects.

A new study by researchers from Boston University and Rockefeller University explains why mosquitoes are so good at detecting us, even when researchers genetically disable human-specific chemoreceptors.

According to the study, at least one species of mosquito, Aedes aegyptihas a totally different way of organizing its olfactory system compared to most animals.

Using CRISPR as a gene-editing tool, the researchers developed mosquitoes whose olfactory neurons would express fluorescent proteins and glow under the microscope when certain odors were nearby. This allowed the researchers to see how different scents stimulated the olfactory system.

Actually A. aegypti connects multiple olfactory sensory receptors to a single neuron, a process called coexpression.

According to this team, this reverses a basic principle of olfactory sciencewhich states that each neuron has only one chemoreceptor associated with it.

“It’s terribly weird” said Meg Younger, neuroscientist at Boston University and lead author. “It’s not what we expected.”

“The central dogma of olfaction is that the sensory neurons, for us in our nose, each express a type of olfactory receptor”, said Younger.

This axiom applies to the bee (Apis mellifera), the tobacco hornworm (manduca sexta) and fruit flies (Drosophila melanogastr), all of which have about the same number of chemosensory receptors as the olfactory glomeruli. (Glomeruli are spherical structures in the brain that receive olfactory signals.)

In A. aegyptihowever, there are at least twice as many receptors as glomeruli, a “striking incompatibility”, the researchers write.

The results indicate an unconventional olfactory system that co-expresses multiple sensory receptors in individual neurons.

“The redundancy afforded by an olfactory system…may increase the robustness of the mosquito olfactory system and explain our long-standing inability to disrupt mosquito detection of humans,” the researchers said. conclude.

The lure of a blood meal is strong, as female mosquitoes must feed on human or animal blood to reproduce.

A long-term goal of research is to create improved mosquito repellents that effectively hide human scent or develop attractants that distract mosquitoes from their meal.

Mosquitoes’ knack for locating humans makes mosquitoes prolific vectors of viral diseases like dengue, Zika, yellow fever, and chikungunya. Collectively, these viruses kill approximately 700,000 people every year.

“As we learn how smell is encoded in their olfactory system, we can create more effective compounds based on their biology,” said Younger.

This article was published in Cell.