Disruption of Circadian Rhythms by Artificial Light Pollution in Nocturnal Insects

Abstract

Artificial light at night (ALAN) poses a growing threat to nocturnal biodiversity, particularly through the disruption of circadian rhythms in sensitive insect species. This study investigated the physiological and behavioral impacts of varying artificial light spectra and intensities on three nocturnal insects—Acheta domesticus, Galleria mellonella, and Photinus pyralis. Insects were exposed to dark (control), low-intensity LED, high-intensity LED, and blue-rich LED lighting conditions in controlled experiments. Behavioral monitoring revealed a significant reduction in locomotor activity under high-intensity and blue-rich LED conditions, with P. pyralis displaying the sharpest decline. Quantitative real-time PCR analyses showed a consistent downregulation of circadian genes (per, tim, clk, and cry) under artificial lighting, particularly in the blue-rich spectrum, indicating severe molecular disruption of internal biological clocks. These gene expression alterations correlated strongly with behavioral impairments and reduced reproductive success. Reproductive metrics, including egg production, hatch rate, and survival, were significantly lower in all ALAN-exposed groups compared to the control, with G. mellonella exhibiting the greatest reproductive decline. Behavioral assays further revealed reductions in courtship and feeding events and an increase in stress-related avoidance behavior. Across all metrics, the blue-rich LED light condition emerged as the most disruptive. These findings provide robust empirical evidence linking ALAN to circadian and reproductive dysregulation in nocturnal insects, underscoring the need for revised lighting practices in ecological and urban planning. By integrating behavioral, genetic, and reproductive endpoints, this study highlights the systemic consequences of light pollution and informs conservation strategies aimed at protecting vulnerable nocturnal insect populations.