Mosquitoes have not become the most productive killer of human animals, being lazy. A new study this week suggests that a common disease-causing species in the United States has learned how to lay stagnant eggs that can survive the harsher winters of the north.
The Asian Tiger Mosquito, or Aedes albopictus It is thought to have first invaded the United States in the mid-1980s, settling in Texas. It quickly expanded and now occurs in much of the Southeastern and Central United States, while its related cousin Ae. aegypti is more likely to cause disease, Ae. albopictus is still capable of spreading Zika, dengue, West Nile, and other viruses that infect the brain.
One strategy that allows the Asian tiger mosquito to survive at a more moderate time is to incorporate its eggs. When mosquitoes "feel" the rough conditions in front of them, which means longer nights caused by winter, they lay more eggs that are able to enter a dormant state. As the days are longer and the conditions are ripe for growth again, these eggs wake up from their sleep and hatch as normal. According to a statement from the University of Washington at St. Louis, eggs are like mosquito capsules.
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The authors of this new study, published in the Journal of Applied Ecology, wanted to see how durable these sleeping eggs really are and whether there are key differences between populations living in the warmer South and those living on the edge of survival in the north.
They mosquitoes and mosquito larvae living north and south, breeding them for several generations, and then leaving new batches of eggs before winter at various locations throughout the country. After the winter was over, they were harvested so researchers could see how well they hatched.
In what may be the only good news, eggs have not survived north of Wisconsin, no matter where they came from. Northern and southern mosquito eggs survive equally well in warmer areas, near the heart of their current range in the US, and in a laboratory simulating the typical winter in Asia where the species originated. But about three-quarters of the northern eggs managed to spend the winter in Pennsylvania, the northernmost area they regularly live in – nearly double the percentage of surviving southern eggs.
According to the authors, these results are that northern tiger mosquitoes have accumulated much better in their new homes than expected. And they have been able to accomplish this feat in an incredibly fast time, evolutionarily speaking.
"All this has happened over 30 years," said lead author Kim Medley, director of the Tyson Research Center at Washington University in St. Louis, in a statement from the university. "This disease vector is evolving rapidly to adapt to the United States. The fact that this has happened with restricted habitat may suggest that there is potential for species to continue to creep more and more north. "
Medley and her team suggest that prolonged adaptation by these mosquitoes" in combination with climate warming may increase the risk of disease exposure to the human population. "So the northern states may be safe for now, that may change soon. And it seems that mosquitoes can be much better at adapting to the changing world than we are.