Transcriptional Response of Circadian Clock Genes to an 'Artificial Light at Night' Pulse in the Cricket Gryllus bimaculatus .

Light is the major signal entraining the circadian clock that regulates physiological and behavioral rhythms in most organisms, including insects. Artificial light at night (ALAN) disrupts the natural light-dark cycle and negatively impacts animals at various levels. We simulated ALAN using dim light stimuli and tested their impact on gene expression in the cricket Gryllus bimaculatus , a model of insect physiology and chronobiology. At night, adult light-dark-regime-raised crickets were exposed for 30 min to a light pulse of 2-40 lx. The relative expression of five circadian-clock-associated genes was compared using qPCR. A dim ALAN pulse elicited tissue-dependent differential expression in some of these genes. The strongest effect was observed in the brain and in the optic lobe, the cricket's circadian pacemaker. The expression of opsin-Long Wave ( opLW ) was upregulated, as well as cryptochrome1-2 ( cry ) and period ( per ). Our findings demonstrate that even a dim ALAN exposure may affect insects at the molecular level, underscoring the impact of ALAN on the circadian clock system.