Comprehensive Evaluation of Bisphenol A Toxicity Reveals Neurobehavioral, Metabolic, and Reproductive Impairments in <i>Girardia tigrina</i>

Bisphenol A (BPA), a common industrial chemical used in plastics and consumer products, is increasingly detected in aquatic environments, raising serious concerns about its potential ecological impacts. This study evaluated the sublethal and acute toxic effects of BPA on the freshwater planarian Girardia tigrina, a recognized model for neurotoxicity and regenerative biology. Acute exposure revealed a time-dependent decrease in LC₅₀ values, from 53.18 μM at 24 h to 22.38 μM at 96 h. Behavioral assays showed significant locomotor impairment, with activity reduced by 36.7% and 57.2% at 1.0 and 5.0 μM, respectively. The LC₅₀ for movement inhibition was estimated at 2.79 μM after only 5 min of exposure. Stereotyped movements intensified with concentration and duration. Reproduction was markedly affected, with fecundity and fertility reduced by 96.7% and 100% at 2.5 μM; no hatchlings emerged at 1.0 or 2.5 μM. Glycogen reserves dropped by 42.9% at 2.5 μM, indicating metabolic disruption. Marked oxidative stress responses were observed, with superoxide dismutase and catalase activities increasing by over 220%. Glutathione S-transferase activity was elevated across all concentrations. Acetylcholinesterase activity showed a biphasic response-strong inhibition at lower doses (-67.8% at 0.1 μM), followed by stimulation at 1.0 μM (+56.9%)-suggesting cholinergic disruption. Collectively, these results demonstrate that BPA disrupts multiple physiological systems in planarians at environmentally relevant levels, underscoring the need for more comprehensive environmental monitoring and the adoption of safer chemical alternatives to protect aquatic biodiversity.