Certain species of mosquitoes have an almost unquenchable need for the blood of humans. Previous efforts to stop mosquitoes from finding humans by interfering with part of their sense of smell were unsuccessful. These efforts were aimed at preventing bites. A recent research provides evidence that it may be due to the fact that the bloodsuckers have built-in workarounds to guarantee that they can always scent humans.
Individual nerve cells in the olfactory system of the majority of animals are only capable of detecting a single kind of odour. But the nerve cells of Aedes aegypti mosquitoes can individually sense a wide variety of odours, according to research published on August 18 in the journal Cell. This indicates that even if a cell were to lose the capacity to pick up on a specific human odour, it would still be able to identify other odours.
This study presents the most complete map to date of a mosquito’s sense of smell. It also implies that it may be more difficult to mask human odours from mosquitoes than researchers previously believed.
It may be particularly challenging to develop mosquito repellents that prevent the insects from associating human odours with their targets. Anandasankar Ray, a neuroscientist at the University of California, Riverside who was not involved in the work, suggests that “maybe instead of trying to mask them from finding us, it would be better to find odorants that mosquitoes don’t like to smell.” “Rather than trying to mask them from finding us, it would be better to find odorants that mosquitoes don’t like to smell,” he says. These kinds of repellents may cause the bloodsuckers to get confused or irritated, which will cause them to flee.
Utilizing an efficient repellent is one of the most important things you can do to stop mosquitoes from spreading disease-causing viruses like dengue and Zika. Olivia Goldman, a neurobiologist at Rockefeller University in New York City, claims that mosquitoes are responsible for more fatalities among humans than any other organism.
When hunting, mosquitoes that feed on humans are attracted to their prey by a multitude of signals, including the heat and odour given off by the person. Insects use their antennae and the little appendages that are located near to their mouths to smell. They are able to detect molecules such as carbon dioxide from exhaled breath or components of body odour by using three different kinds of sensors that are located in the olfactory nerve cells.
In earlier studies, researchers hypothesised that turning off certain sensors might prevent mosquitoes from detecting human odours by interfering with the signals that are transmitted to the brain through the nose. However, according to neurobiologist Margo Herre, who is also affiliated with Rockefeller University, mosquitoes without sensory organs may still detect the presence of humans and bite them.
Therefore, Goldman, Herre, and their colleagues attached fluorescent labels to the nerve cells, also known as neurons, of the Aedes aegypti mosquito in order to gain fresh insights into the process by which the insect brain interprets human scents. Surprisingly, the scientists discovered that individual mosquito neurons seem more like sensory hubs than the traditional single kind of sensor that is seen in each nerve cell.
The results of genetic investigations showed that some of the nerve cells in the olfactory bulb included more than one kind of sensor. In response to many mosquito-attracting compounds prevalent in humans, such as octenol and triethyl amine, some cells generated electrical impulses, which is a hint that the neurons could detect more than one kind of odour molecule. A further research that was conducted in the month of April and published in the journal eLife discovered comparable findings in fruit flies, which shows that a system like this may be prevalent among insects.
It is not obvious why mosquitoes would find it beneficial to have many methods of sensing the scents that humans give out. According to Meg Younger, a neurobiologist at Boston University and one of the study’s coauthors, “Different people’s sense of smell may be rather distinct from one another.” “Perhaps this is a setup to discover a human, and it doesn’t matter what kind of human body odour the person is releasing; it doesn’t matter,” she said.