Mosquitoes Have Evolved Olfactory System for Hunting Human Scents, Study Reveals

According to a study, mosquitoes have an olfactory system that has evolved specifically for detecting human scents.

Female mosquitoes detect a distinctive concoction of body odors we release into the atmosphere when they are searching for a human to bite. The mosquitoes' antennae are then stimulated by these odors. To make people invisible to mosquitoes, researchers have tried removing these receptors.

However, mosquitoes still manage to bite us despite having an entire group of odor-sensing receptors removed from their genome. Recently, a team of researchers discovered that mosquitoes have redundant fail-safes in their olfactory system that ensure they can always detect our odors. Their findings were published in the journal Cell on August 18th.

Margo Herre, a scientist at Rockefeller University said that mosquitoes defy all accepted theories about how animals perceive smell. One of the study's principal authors is Herre.

One vs. Many

An olfactory neuron in the majority of animals can only recognize one kind of odor.

According to Leslie Vosshall, a professor from the Howard Hughes Medical Institute at Rockefeller University, if a person loses just one odorant receptor, all the neurons that convey that receptor will become insensitive to smells. Vosshall is the senior author of the study. However, she and her fellow researchers discovered that this is not true of mosquitoes.

Vosshall says that since eliminating a single receptor has had no impact, more research is required to eradicate mosquitoes. The unstoppable human attraction to mosquitoes must be considered in any future efforts to control them with repellents or other methods.

Meg Younger, a professor at Boston University, said that unexpectedly, the project began when researchers were examining the mosquito brain's encoding of human odor. Younger is one of the lead authors of the study.

Read also: Mosquito Bite Can Be Trumped by Circadian Rhythm, New Study Reveals 

Evolved and Redundant

They discovered that amines, another class of chemical used by mosquitoes to search for humans, also stimulate neurons that are prompted by the human odor 1-octen-3-ol. This is unusual because all known theories about how animals perceive smell suggest that 1-octen-3-ol neurons should not have been able to detect amines because they encode odor with narrow specificity.

Younger said that surprisingly, 1-octen-3-ol and amine receptor-sensitive neurons did not belong to separate populations. This may serve as a fail-safe, allowing all human-related odors to trigger "the human-detecting part" of a mosquito's brain even if some receptors are lost.

To determine which additional receptors are expressed by specific mosquito olfactory neurons, the team also used single-nucleus RNA sequencing.

Olivia Goldman, another lead author of the study, said that the outcome provided the team with a comprehensive understanding of how frequent the co-expression of receptors is for mosquitoes.

According to Vosshall, other insects might have a comparable mechanism. The Johns Hopkins University research team of Christopher Potter recently discovered that fruit flies' neurons co-express similar receptors. Vosshall said that this may be a general strategy for insects that depend heavily on their sense of smell.

The goal of Meg Younger's team is to eventually determine the functional relevance of the co-expression of various olfactory receptor types, Science Daily reports.

Related article: Viruses from Mosquito Bites Could Alter Your Body Odor to be More Attractive to Mosquitoes