The highest levels of West Nile virus transmission occur in late summer and early fall in Ohio. If
People who postpone or delay diapause and continue to be active long into the year may be at greatest risk of contracting West Nile virus.
This study is one of the first to show that artificial light at night can have significant effects on mosquito behavior – including effects that are not necessarily predictable. The same urban lights at night can have very different effects in different seasonal contexts.
Importance of daylight in survival of mosquito
Diapause for female northern house mosquitoes (Culex pipiens) is not quite a winter sleep, but rather a period of inactivity when the insects live in caves, culverts, sheds, and other semi-protected places. Before winter arrives, mosquitoes convert sweet sources like plant nectar into fat.
As the days grow longer, females begin to forage for blood meals to enable egg production. Some become infected with West Nile virus by eating infected birds, and later transmit the virus when they feed on people, horses, and other mammals.
This study builds on two previous findings that circadian clock genes differ between diapausing and non-diapausing mosquitoes, strongly suggesting when diapause should begin.
And recent work also found that exposure of female mosquitoes to dim light at night reduced diapause and made them more active for reproduction – even though shorter days indicated they should be dormant.
In the current study, the researchers followed both lines of inquiry by comparing daily activity and nutrient accumulation by mosquitoes reared under two laboratory conditions – long days mimicking the insects’ active season and without exposure to artificial light. – Short days that induce inactivity. Night.
The study provided more evidence linking the circadian patterns of mosquito behavior, showing that while the insects’ activity decreases during diapause, the circadian rhythmicity of that activity persists during this dormant period.
What do city lights mean for mosquito bites?
Exposure to light pollution reduced the number of water-soluble carbohydrates – sugars that are an essential food source during winter – that were accumulated by mosquitoes in both tall and short conditions.
Exposure to artificial light at night reversed the accumulation patterns of the sugar glycogen: under normal conditions, non-dormant mosquitoes had plenty of glycogen in their bodies but diapausing insects did not – but in mosquitoes subjected to light pollution, longer Long-day mosquitoes did not accumulate much glycogen, and short-day mosquitoes showed increased glycogen accumulation.
The researchers observed a consistent trend in the activity-related effects of light at night, with slightly increased activity among inactive mosquitoes and slightly suppressed activity among long-dwelling mosquitoes expected to be busy searching for food.
Although the findings were not statistically significant, the combined observations suggest that light pollution causes mosquitoes to break away from diapause – perhaps by scrambling signals from their circadian clock.
This may be bad for mammals in the short term as mosquitoes potentially end up biting us later in the season, but it may also be bad for mosquitoes in the long term as they engage in preparatory activities needed to survive during the winter. may fail completely. diapause. The researchers plan to conduct field studies to see if these lab findings hold up in the wild.