Circadian Rhythm Alterations in Aedes aegypti Mosquitoes Exposed to Artificial Night Lighting

Abstract

Artificial light at night (ALAN) is a new type of anthropogenic environmental pollutant disrupts the natural light-dark cycle and affects animal behaviour and processes in the ecosystem. This paper examines how ALAN affects circadian, gene expression, and behavioural ecology of Aedes aegypti, a key dengue and Zika virus vector, and a primary scourge. Four lighting conditions were tested in laboratory experiments, which included natural 12:12 light to dark cycle (control) and low-intensity white LED (5 lux), moderate-intensity white LED (20 lux), and narrow-spectrum blue LED (20 lux). The infrared beam-break systems that served to monitor locomotor activity showed that the period significantly increased in controls (24.0±0.1 h) to 24.8±0.2 h during blue ALAN (p<0.001). The analysis of the quantitative PCR demonstrated the suppression of the core clock genes, period and timeless were suppressed by 3.2-fold and 2.8-fold, respectively, in the subjective night. The behavioural tests showed that there was an increase in the nocturnal biting behaviour of 67% when compared to the time when they were supposed to be inactive (02:00 to 04:00) indicating that there were changes in the host-vector interaction. The reproductive fitness was greatly impaired, feedcundity was decreased by 23% and hatchability of eggs by 18% and melatonin levels decreased by 41%. These results confirm that ALAN interferes with the organization of circadian at the molecular and behavioural level with ecological outcomes that could affect the dynamics of vectors and the spread of diseases in cities. The research paper emphasizes the relevance of lighting approaches that are sustainable to the environment, especially spectral management of the effects of light pollution on the ecological and human health aspects.