A recent study conducted by researchers at The Ohio State University reveals that urban light pollution may have a significant impact on the winter dormancy period, or diapause, of mosquitoes and mosquito biting season that transmit West Nile virus. This discovery carries both positive and negative implications for public health.
On a positive note, the research suggests that if mosquitoes are unable to enter their diapause period and accumulate sufficient fat reserves, they may not survive the winter. However, the negative side of the equation is that the disruption of diapause could lead to mosquitoes remaining active and biting humans and animals later into the fall.
Study senior author Professor Megan Meuti explained the potential consequences of this disruption: “We see the highest levels of West Nile virus transmission in the late summer and early fall in Ohio. If you have mosquitoes postponing or delaying diapause and continuing to be active longer in the year, that’s at a time when the mosquitoes are most likely to be infected with West Nile virus and people could be at greatest risk of contracting it.”
The study is among the first to demonstrate the potential effects of artificial light at night on mosquito behavior. Interestingly, the researchers found that the impact of urban light pollution on mosquitoes is not entirely predictable, as the same light sources can produce varying effects depending on the season.
For the study, which was recently published in the journal Insects, Meuti collaborated with study first author Matthew Wolkoff and Lydia Fyie, both PhD candidates in Entomology at Ohio State,
The research focused on the diapause of female Northern house mosquitoes (Culex pipiens), which is not a complete winter slumber but rather a period of dormancy during which the insects reside in semi-protected locations such as caves, culverts, and sheds. Before winter arrives, mosquitoes convert sugary substances like plant nectar into fat, which sustains them during diapause.
As the days grow longer, female mosquitoes begin searching for blood meals to enable egg production. Some of these mosquitoes become infected with West Nile virus after feeding on infected birds, subsequently transmitting the virus to humans, horses, and other mammals during subsequent feedings.
The study builds upon two earlier findings from Meuti’s lab, including the discovery that circadian clock genes differ between diapausing and non-diapausing mosquitoes, strongly indicating that day length determines the onset of diapause. More recently, research led by Fyie revealed that female mosquitoes exposed to dim light at night averted diapause and became reproductively active, even when shorter days suggested they should be dormant.
In a recent study led by Wolkoff, researchers have discovered that artificial light at night has a significant impact on mosquito behavior and nutrient accumulation. The findings, which could have implications for both humans and mosquito populations, shed new light on the complex relationship between insects and their environment.
To explore this relationship, the research team studied mosquitoes in two different laboratory settings: one simulating long days, which correspond to the insects’ active season, and another with short days, inducing a period of dormancy called diapause. In each condition, mosquitoes were exposed to artificial light at night.
The study uncovered further evidence linking mosquito behavior to circadian patterns. During diapause, the insects’ activity levels decreased, but their circadian rhythmicity remained consistent. This finding suggests that even in periods of dormancy, mosquitoes maintain a predictable pattern of activity.
However, the introduction of artificial light at night disrupted these patterns and influenced the mosquitoes’ ability to accumulate nutrient reserves, which are crucial for surviving winter temperatures. For example, exposure to light pollution reduced the amount of water-soluble carbohydrates – a vital food source during winter – accumulated by mosquitoes in both long- and short-day conditions.
Additionally, the researchers found that the accumulation of glycogen, a type of sugar, was altered by exposure to artificial light at night. Under normal conditions, non-dormant mosquitoes had high levels of glycogen, while diapausing mosquitoes did not. But when subjected to light pollution, long-day mosquitoes accumulated less glycogen, and short-day mosquitoes saw an increase in glycogen accumulation.
In terms of activity, the researchers observed consistent trends when mosquitoes were exposed to artificial light at night. Dormant mosquitoes exhibited a slight increase in activity, while long-day mosquitoes showed slightly suppressed activity. Although these results were not statistically significant, Wolkoff believes the combined observations suggest that light pollution may disrupt diapause in mosquitoes by interfering with signals from their circadian clock.
“This could be bad for mammals in the short term because mosquitoes are potentially biting us later in the season, but it could also be bad for mosquitoes in the long term because they might be failing to fully engage in preparatory activities they need to survive the winter during diapause, and that might reduce their survival rate,” explained Wolkoff.
The findings highlight the need for further research to better understand the complex relationship between urban light pollution, mosquito behavior, and the transmission of West Nile virus. Developing strategies to mitigate the potential risks associated with disrupted diapause could prove essential in protecting public health from the spread of mosquito-borne diseases like West Nile virus.
To confirm the validity of these lab results, the research team plans to conduct field studies to examine the effects of artificial light at night on mosquitoes in their natural environment. Such studies could provide valuable insights into the role of light pollution in altering mosquito behavior and survival, potentially impacting ecosystems and human health.
Over the years, researchers have made significant progress in understanding mosquito behavior, biology, and disease transmission, which has led to the development of various innovative strategies to prevent the spread of mosquito-borne diseases. Some notable advances include:
These advances, along with continued research and collaboration between scientists, policymakers, and communities, have the potential to significantly reduce the impact of mosquito-borne diseases on global public health.