A new study from the University of California at Riverside facilitates the ability of humans to “switch off” proteins that activate mosquito sperm, which would prevent these sperm from swimming or fertilizing the eggs of females.
This work, say the researchers, might help control the populations of the Culexthe most common mosquito that transmits encephalitis and West Nile virus.
“During mating, mosquitoes stick together tail to tail, and the males transfer their sperm into the female reproductive duct. It can be stored there for a while, but it must still circulate from point A to point B to complete fertilization,” says Cathy Thaler, lead author of the study and specialist in cell biology.
At the heart of this process are specialized proteins that are secreted during ejaculation; these proteins activate the flagella of the spermatozoa, ie the “tail” which allows their movement.
“Without these proteins, the sperm cannot enter the eggs. The spermatozoa remain immobile, and will eventually degrade”, specifies Richard Cardullo, professor of biology and also author of the study.
The research, detailed in the scientific publication PLOS ONEprovides an overview of all the proteins in mosquito sperm, helping to identify those that maintain sperm quality when inactive, and which are then activated to allow movement.
To obtain this information, the research team used students who isolated up to 200 male mosquitoes from a larger population. They then extracted enough sperm from their tiny reproductive duct for mass spectrometry equipment to detect and identify the proteins.
Previously, specialists had determined that sperm needed calcium when entering a reproductive duct to fuel the forward movement. “Now we can look at the complete protein profile we created, identify calcium-bound proteins, and design experiments to target these transport channels,” says Cardullo.
This kind of protein targeting offers an avenue of mosquito control that is “greener” than other approaches that can have unexpected toxic impacts. “We stopped spreading pesticides everywhere, because it kills all insects, good and bad, in addition to harming other animals,” recalls Ms. Thaler.
“Our work lays the foundation for some form of biological control, which would probably be preferable,” adds Cardullo.
The important word here, write the researchers, is indeed “control”, not eradication. Although immobilizing sperm would be 100% effective for treated mosquitoes, it is not possible, or even desirable, to kill them all. This technology would change the proportion of fertile males within a given mosquito population, rather than eradicating them all, say the specialists.
“Mosquitoes are the most dangerous animals on Earth. But as much as people hate them, most environmentalists would oppose a plan to eradicate them. They do, following all, play an important role in the food chain of fish and other animals,” continues Cardullo.
The research team hopes that this information regarding mosquitoes Culex might also be used to control populations of other mosquito species. As the climate crisis escalates, many other species of this insect, including those that transmit malaria, are moving to the northern hemisphere.
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