Rapid industrialization and coastal development have driven the widespread accumulation of heavy metals (HMs) in marine environments, particularly in sediments and surrounding waters. Heavy metal contamination poses a significant threat to benthic ecosystems and coastal environmental health, highlighting the need for a better understanding of their toxic effects on marine organisms. Perinereis linea is a sediment-dwelling marine polychaete recognized as a sensitive bioindicator of coastal environmental conditions. Through its burrowing activity, P. linea contributes to sediment bioturbation, promoting the mineralization and decomposition of organic matter and supporting the health and stability of benthic ecosystems. Despite its ecological importance, few studies have investigated P. linea as a potential model organism for toxicity assessment, particularly in terms of behavioral responses. In this study, we evaluated the potential of P. linea as a marine model for assessing the behavioral toxicity of HMs using the customized behavioral analysis platform. Behavioral screening of 23 HMs revealed significant locomotor impairments induced by most of the tested metals, characterized by reduced average speed and rapid movement time ratio, increased freezing behavior, and altered movement complexity. PCA and heatmap further identified distinct behavioral fingerprints among the tested metals, with copper exhibiting the strongest behavioral toxicity. Subsequent dose-response experiments demonstrated that copper exposure (1-1000 ppb) significantly reduced locomotor activity and fractal dimension, indicating impaired movement complexity. Co-exposure with chelating agents, including citric acid, chitosan, tannic acid, and sodium alginate, partially restored normal behavioral patterns. Furthermore, transcriptomic findings provided preliminary insights into the potential molecular mechanism underlying HM-induced effects in P. linea. However, given the limited biological replication, the transcriptomic findings should be considered exploratory and interpreted with caution. Collectively, these findings demonstrate the potential of P. linea as a promising marine model organism for behavioral toxicity assessment and environmental monitoring of metal contamination in marine ecosystems.
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