Scientists have just created mutant mosquitoes that cannot see contrasts. Although they are not completely blind, they can no longer find their way to their prey. An original strategy to fight mosquitoes carried diseases.
Imagine being able to become invisible to mosquitoes. They could pass by without noticing you and become as harmless as flies. Researchers at the University of California Santa Barbara have just performed a small miracle: they have created a genetically modified mosquito that is “blind” to contrasts and is therefore unable to find its hosts.
Mosquitoes are attracted to dark colors
Female mosquitoes first detect their hosts by body odor when they are in close proximity. Some studies have also found that mosquitoes prefer different blood types or skin bacteria. But before that, mosquitoes use two signals: CO2 and visual signals. Several studies have shown that Aedes aegypti mosquitoes are particularly attracted to people wearing dark clothes. “Even in the absence of humans, CO2 encourages mosquitoes to search for darker images,” confirms Yinpeng Zhan, a Ph.D. student at the University of California and lead author of a study recently published in Current Biology. When mosquitoes approach a target within a few centimeters based on these visual cues, they use body odor to determine whether the target is a potential host or not.
A mutant mosquito that cant detect contrasts
The idea was simple: to make the mosquito blind so that it could not detect its prey. Using CRISPR-Cas9, the researchers removed two proteins expressed in mosquito eyes – rhodopsin Op1 and rhodopsin Op2. They found that when exposed to CO2 (simulating breathing), the little mutants lost the ability to go towards white and black dots. Note that mosquitoes did not become blind because their eyes still respond to light stimuli. They have simply become insensitive to contrast and are unable to “hunt” prey on the basis of dark colors. “Removal of Op1 and Op2 likely reduces sensitivity to light below a certain threshold required for the mosquito to reach the target,” the authors write.
Killing mosquitoes by starving them
It is important to note that this study was carried out in a laboratory and the researchers did not work with real prey. It is, therefore, possible that these mutant mosquitoes are still able to detect humans with their other senses, albeit with less accuracy and confidence. However, this discovery could be a new weapon to help eradicate mosquitoes, which cause millions of deaths each year by transmitting disease agents (Zika, chikungunya, Malaria, etc.). “If female mosquitoes don’t see their hosts, it will be harder for them to find the blood they need to develop eggs, and the population will decline,” according to the study co-author Craig Montel.