Vectors of diseases such as dengue, yellow fever, and malaria, mosquitoes are by many considered pests and threats to public health.
Although they are insects to which we rarely devote more than a few seconds of thought (except on a hot summer night when one is buzzing through our room), mosquitoes are creatures that still hide some secrets. One of them relates to the role of the females in mating.
With a relatively short average lifespan (ranging from a few weeks to a few months, depending on the species), reproduction in mosquitoes is a highly important event, especially because females mate only once in their life. They mate once, but reproduce several times, by storing in their bodies the sperm of the male with whom they copulated.
For a long time it was thought that female mosquitoes passively accepted advances from any male, but this idea has now been debunked by a group of scientists at Rockefeller University, in the United States of America.
The team started from what it considered to be a paradox: if females do not have decision-making power, why would several males mate with them during their lifetime?
In an article published in the journal ‘Current Biology’, the researchers show that, after all, it is the females who set the rules of the game and are they who decide whether there is copulation with a given male that approaches them with the aim of mating. After receiving the male’s sperm, the female mosquito does not copulate again, regardless of the suitors’ persistence.
“In biology there has long been the assumption that males have agency and that females are passive,” says, in a statement, Leslie Vosshall, lead co-author. “This study reminds us that those assumptions can hinder understanding of what is really happening, even in something as well studied as mosquito reproduction.”
This investigation focused on two species of mosquitoes: the yellow fever mosquitoes (Aedes aegypti) and the Asian tiger mosquito (Aedes albopictus). In the laboratory, they used genetic manipulation techniques to make the males’ sperm fluorescent. Then, using high-speed and high-resolution cameras, they filmed the interactions between males and females.
When the males touched with the tips of their genitals the genital organs of a female that had not yet mated in her life, she, if she accepted, extended her genitals, to allow the transfer of sperm, in a process that did not take more than half a minute. The scientists say that this elongation of the female genitalia is crucial, because, if this does not happen, there is no copulation, no matter how much the male may try. Thus, the females are the ones who decide whether there is mating, and not the male.
In the case of interactions between males and females that have already mated somewhere in their life, there is no elongation of the female genital organs and, therefore, there is no copulation.
The same behaviour was recorded in both species of mosquitoes, which diverged from one another about 35 million years ago, so the researchers say that female control over reproduction in mosquitoes is something that has existed for a long time.
