Behavioral and redox effects of lithium and curcumin in a planarian model of sublethal stress

Freshwater ecosystems are increasingly contaminated by neuroactive compounds, including lithium (Li) from battery waste and curcumin (CUR) from consumer products, but their sublethal effects on aquatic invertebrates are poorly characterized. Linking behavioral alterations to biochemical responses under sublethal exposure remains a challenge. We used Girardia tigrina to assess behavioral and redox responses to mechanical, photic, and predator odor stress, followed by Li or CUR treatment. Mechanical and predator-odor stress increased time in the illuminated compartment by 40-60% (p < 0.0001), whereas light stress decreased it by ~35% (p < 0.001). CUR shifted responses toward control levels across all stressors (p > 0.05 vs. controls), while Li showed persistent effects under mechanical and predator-odor stress (p < 0.05). SOD activity increased 1.5-2.0-fold (p < 0.01); GST was reduced by stress and further decreased by treatments (p < 0.05). These findings support G. tigrina as a model for sublethal neurotoxicity.