Artificial light at night induces opposing neurotoxic effects in adult and larval zebrafish

Artificial light at night (ALAN) has become a widespread environmental pollutant, altering natural light-dark cycles and posing significant risks to aquatic ecosystems. Fish are particularly sensitive to ALAN. While most existing studies have focused on the effects of ALAN on adult fish, its impacts during early developmental stages remain largely unexplored. In this study, we examined the stage-specific neurobehavioral and molecular responses of both adult and larval zebrafish exposed to ALAN. Based on our field research of ALAN, we exposed zebrafish to different wavelengths: red (628 nm), green (519 nm), and blue (465 nm) under 0.26 μmol·m⁻²·s⁻¹ photon flux densities. Larval zebrafish were exposed for 6 days, while adult zebrafish were exposed for 14 days. Results showed that adult zebrafish exhibited significant anxiety-like behaviors when exposed to red and blue ALAN, whereas larvae showed reduced anxiety-like responses under the same conditions. Consistent with these behavioral patterns, neurochemical assays further demonstrated that catecholaminergic pathways were activated in adults but suppressed in larvae under red and blue ALAN exposure. Green ALAN caused minimal changes in both stages. These findings highlight the stage-specific neurotoxic risks of ALAN and provide mechanistic evidence linking catecholaminergic dysregulation to altered anxiety-like behaviors. They also offer significant mechanistic insights into how different colors of ALAN affected neural regulation in fish. Overall, this study provides guidance for ecological risk assessments of ALAN and highlights the importance of considering light spectrum and life stage in the development of aquatic lighting management strategies.