The Effects of Artificial Light at Night on Nocturnal Insect Immunity

Exposure to artificial light at night (ALAN) has negative impacts on endogenous circadian rhythms in animals, which has known negative endocrinological effects on immune functioning. While this is well studied in vertebrates, there is less research on immunological impacts for invertebrates. To address this research gap, we assessed the impact of ALAN over the course of a biologically relevant timescale in the Pacific field cricket, Teleogryllus oceanicus, a model invertebrate species. We reared crickets under a 12 hr daylight (2600 lx) 12 hr dark (0 lx) or relevant ALAN (50 lx & 100 lx) cycle for their entire adult life (28 +/- 3 days) then took hemolymph samples and performed an encapsulation assay, which are two established measures of insect immune function. We found that crickets reared under the 50 lx treatment had an upregulated encapsulation response compared to the control and 100 lx crickets and that male crickets reared under the 100 lx ALAN had the highest mortality rate. Our data suggests that contrary to previous studies, the emergent process of mounting an encapsulation response may be more susceptible to the effects of ALAN than circulating immune cell number. Additionally, it appears that there are sex based differences in mortality effects of intense levels of ALAN which could have significant impact on population demographics.