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Mosquitoes have not become the most prolific animal killers of humanity by being lazy. A new study this week suggests that a common species causing disease in the United States has learned to lay dormant eggs that can survive during the harshest winters in the North.
The Asian tiger mosquito, or Aedes albopictus, is believed to have invaded the United States in the mid-1980s and settled in Texas. It has rapidly expanded its range and is now found in much of the southeastern and central United States. Ae. aegypti is more likely to cause illness, Ae. albopictus is still able to transmit Zika virus, dengue, West Nile virus and other viruses that infect the brain.
A strategy that has allowed the Asian tiger mosquito to survive in temperate weather involves its eggs. When mosquitoes "feel" the harsh conditions that await them, that is, the long nights caused by winter, they lay more eggs able to go dormant. Once the days are longer and the conditions are ripe again for growth, these eggs come out of their sleep and hatch normally. As a statement from Washington University in St. Louis says, eggs look like mosquito capsules.
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The authors of this new study, published in the Journal of Applied Ecology, wanted to know how these dormant eggs were sustainable, and whether there were major differences between populations living in the warmer south and those living at the edge of survival in the area. North.
They collected eggs and larvae of mosquitoes living in the North and South, raised them for several generations, and then left new batches of eggs before winter in various parts of the country. Once the winter ended, they were assembled so that researchers could determine the number of successful outbreaks.
In what could be the only good news, eggs could not survive as far north as Wisconsin, regardless of their origin. Mosquito eggs from the north and south also survived in the warmer areas near the core of their current US range, as well as in a laboratory simulating the typical winter of Asia. Origin of the species. But about three-quarters of the eggs in the north survived the winter in Pennsylvania, the northernmost range where they regularly live – almost double the percentage of southern eggs that survived.
According to the authors, the results suggest that northern tiger mosquitoes have acclimatized much better than expected at their new home. And they managed to accomplish this feat in an incredibly fast time, from the point of view of evolution.
"All this has happened in 30 years," said lead author Kim Medley, director of the Tyson Research Center at Washington University in St. Louis, in a university press release. "This disease vector has evolved rapidly to adapt to the United States. The fact that this occurred at a range limit might suggest that the species may continue to move further north. "
Medley and his team believe that the ongoing adaptation of these mosquitoes "combined with global warming could increase the risk of exposure to the disease for human populations." Thus, the northern states could be safe for the moment, but they could soon change. And it seems that mosquitoes are much better adapted than us to adaptation to a changing world.
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