Artificial light is a feature accompanying the vast majority of human settlements. Together with growing urbanisation it presents a global phenomenon of increasing importance.
Light stimuli are directly used to inform the circadian clock and are hence a key component of timekeeping. The internal clock regulates, directly or indirectly, a large number of physiological downstream processes, among them are daily activity and seasonal behaviours. Some of these systems are well studied, i.e. the circadian clock, and yet we lack knowledge on whether and how artificial light influences downstream, processes, such as daily movement patterns and reproductive output.
Some mosquito species, among them Culex pipiens, occur in close proximity to humans and artificial light at night becomes therefore part of their habitat. Culex pipiens is distributed globally and acts as a principal vector for West Nile Virus in many parts of the world.
We examined the effect of extended periods with artificial light on the mosquito Culex pipiens f. molestus by means of gene expression analysis of circadian clock genes, daily activity patterns and egg production. There are pronounced differences in the behaviour and the physiology of male and female mosquitoes. Therefore, we investigated sex specific differences as this will have implications at population level adding to effects present at an individual level.
All areas under study were influenced by our experimental set up and showed sex-specific responses indicating potentially large effects on population level. Gene expression was affected in four out of five analysed genes (mainly down-regulation) and activity was significantly reduced throughout the day. Egg production was also negatively affected suggesting that the forthcoming generation could also be influenced.