Knowledge Bank

Female Northern house mosquitoes, Culex pipiens, transmit serious pathogens including West Nile virus, and survive the winter by entering diapause, an arrested state in which the females store fats and stop blood feeding and reproductive processes. Diapause is cued by photoperiod, so as days become shorter in late summer and early fall, mosquitoes stop biting vertebrates which effectively stops the disease transmission period. Artificial light at night (ALAN) has been shown to cause C. pipiens to avert diapause in the lab. However, we do not know if ALAN in the field causes similar effects, or the molecular mechanisms underlying how ALAN inhibits the diapause response. To determine whether ALAN in the field stimulates blood feeding in mosquitoes I measured the proportion of field-reared ALAN-exposed and unexposed mosquitoes that consumed a blood meal. I found that field exposure to ALAN caused mosquitoes to blood-feed at a higher rate than unexposed mosquitoes, indicating ALAN in the field delays diapause initiation and prolongs the mosquito biting season. I also characterized the relative abundance of Insulin-like peptide-1 (Ilp1) and allatotropin transcripts in ALAN-exposed and unexposed mosquitoes using quantitative real time PCR. I hypothesized that exposure to ALAN in the field would increase the rate of blood feeding in mosquitoes. I also predicted that Ilp1 and allatotropin would be more abundant in the ALAN-exposed mosquitoes as this would allow them to better process blood meals and maintain lower levels of fat than their non-ALAN-exposed, diapausing counterparts. I found that Ilp1 was significantly downregulated in ALAN-exposed mosquitoes compared to the unexposed control females. In contrast, alltotropin was significantly upregulated in ALAN-exposed mosquitoes relative to their diapausing counterparts. Overall, these results demonstrate that ALAN disrupts seasonal responses in mosquitoes, effectively postponing diapause entry and altering the regulation of seasonal response genes.