Anderson, G. E. | bioRxiv Science

bioRxiv2025

Artificial Light at Night Disrupts Circadian and Metabolic Gene Expression in the Green Anole Lizard (Anolis carolinensis): A Transcriptomic Analysis

Artificial light at night (ALAN) disrupts natural light-dark cycles, posing ecological challenges for wildlife in urban areas. Here we investigated the effects of ALAN on gene expression in the brain, liver, and skin of green anole lizards (Anolis carolinensis) whose urban populations are increasingly exposed to light pollution. To identify genetic pathways impacted by ALAN exposure we analysed expression of genes associated with circadian and metabolic regulation at midday, midnight and at midnight with artificial light. Differential expression analysis revealed that clock-related genes (PER1, NR1D1, CRY2) were significantly altered in the brain, liver, and skin following ALAN treatment and genes involved in glucagon regulation (GCG) and lipid metabolism (NOCT) were differentially expressed in the liver, indicating metabolic disruptions. Skin exhibited unique responses to ALAN suggesting that repair responses may be altered as genes related to cellular processes, such as wound healing, were upregulated under normal light and dark conditions. Our findings also show that ALAN disrupts core circadian genes, impacting physiological processes including hormone regulation, glucose homeostasis, and potentially reproductive cycles. This study provides the first transcriptomic evidence of the effects of light pollution on green anoles, highlighting the need to preserve natural light cycles in urban habitats. An interactive online database developed for this study allows further exploration of gene expression changes, to promote research on artificial light-polluted environments.

genetics↗

bioRxiv2025

Expression of Non-Visual Opsins in the Green Anole Lizard (Anolis carolinensis)

Extra-retinal photoreception is widely observed across vertebrates, facilitating species-specific regulation of physiological and behavioral responses to diverse photic environments. Yet, the roles of non-visual opsins remain poorly understood, as their distribution and function have not yet been systematically investigated. This study provides the first comprehensive evidence of non-visual opsin expression across the reptile body. Using predicted sequences for extra-retinal photoreceptors, non-visual opsins were confirmed in the brain, eye, testes, liver, and skin. Specifically, OPN3 (encephalopsin) exhibited the highest expression across all tissues, particularly in the testes, corroborating findings in mammals. OPN5 (neuropsin) was detected predominantly in the testes, marking the first such report in reptiles. Moderate expression of OPN4 (melanopsin) in the brain and eye supports its roles in both visual and deep-brain photoreception. In the skin, a distinct pattern of higher opsin expression was observed in the dorsal skin compared to ventral skin. OPN3-3 was most abundant and exhibited a unique expression profile, potentially linking opsins to light-mediated processes influencing chromatophore-driven color changes. Findings from this research provide a critical evolutionary context for understanding the role and conservation of non-visual opsins in reptiles and their relevance to vertebrate lineages, including mammals and birds.

zoology↗