Various studies in recent years have analyzed the effects of light pollution on insects, generally indicating that many of the light sources in urban areas alter the lives of many of these species and cause damage and loss of very important populations.
A new scientific investigation, with few similar precedents, now points out that artificial lighting in urban areas may be facilitating the extension of the season of presence and activity (human bites) of some mosquitoes, among which are potentially disease-carrying species .
The results of this study, published in the scientific journal Insects by researchers from Ohio State University (United States), refer to a specific species and laboratory tests but suggest the need to analyze the problem more thoroughly and on a global scale.
The authors indicate that, in the case studied, with Culex pipiens mosquitoes (common mosquito, possible transmitter of West Nile virus), light pollution in urban areas alters the period of inactivity (diapause) of these insects, which means that they are biting. humans and animals longer in the fall.
"We see the highest levels of West Nile virus transmission in the late summer and early fall in Ohio. If there are mosquitoes that postpone or delay diapause and continue to be active longer in the year, that's the time it's more likely than mosquitoes infected with West Nile virus and people may be at higher risk of contracting it," said Megan Meuti, lead author of the study and an assistant professor of entomology at The Ohio State University.
This study and previous findings by Megan Meuti and her team are among the first to show that artificial light at night could have a significant impact on mosquito behavior, including effects that are not necessarily predictable.
"We are discovering that the same urban light at night can have very different effects in different seasonal contexts," said the lead author of the new study in statements released by her university. The results obtained in this study correspond to laboratory tests and must still be verified in field tests, that is, in an urban environment and real artificial lighting sources.
Diapause for domestic Culex pipiens mosquitoes is not exactly winter sleep, but rather a period of dormancy in which the insects live in caves, sewers, sheds, and other semi-sheltered places. Before winter sets in, mosquitoes convert sugary sources, such as plant nectar, into fat. As the days get longer, the females begin to take a blood meal to allow for egg production. Some become infected with West Nile virus by feeding on infected birds and then transmit the virus when they feed on people, horses and other mammals, the authors say, referring specifically to Ohio.
An earlier study led by Lydia Fye, also a participant in the new research, found that female mosquitoes exposed to dim light at night avoided diapause and became reproductively active, even when short days indicated they should be inactive.
Now, the researchers followed the lines of study already begun by comparing the daily activity and nutrient accumulation of mosquitoes reared under two laboratory conditions: long days that mimic the insects' active season and short days that induce dormancy, with and no exposure to artificial light at night.
The study provided further evidence associated with a circadian pattern in mosquito behavior, showing that the insect's activity declines during diapause, but the circadian rhythm of that activity is maintained even during this period of inactivity.
"The introduction of artificial light at night was found to affect these activity patterns and influence the acquisition of nutrient reserves necessary for mosquitoes to fatten and withstand winter temperatures," states the briefing released by the State University of Ohio.
The researchers observed consistent trends in the activity-related effects of light at night, with slightly increased activity among inactive mosquitoes and slightly suppressed activity among long-day mosquitoes expected to be busy foraging. Although the findings were not statistically significant, Wolkoff said the combined observations suggest that light pollution causes mosquitoes to avoid diapause, perhaps by encoding their circadian clock signals.
"This could be bad for mammals in the short term because mosquitoes could bite us later in the season, but it could also be bad for mosquitoes in the long term because they might not fully participate in the preparatory activities they need to survive the winter during the season. diapause, and that could reduce their survival rate," said Matthe Wolkoff, co-author and first signatory of the study.
