Behavioral and Molecular Effects of 2,4-Dichlorophenoxyacetic Acid Exposure in Planarians

The widespread use of pesticides, such as 2,4-dichlorophenoxyacetic acid (2,4-D), raises serious concerns about their effects on non-target aquatic organisms. In vertebrates, 2,4-D has been associated with neurotoxic outcomes. Planarians offer a valuable system for toxicological studies because of their well-characterized nervous system, regenerative capacity, and measurable behavioral responses. This study investigated the neurotoxic effects of 2,4-D exposure in the planarian species Girardia dorotocephala, including the assessment of nociceptive behaviors, survival rate, phototactic responses, and DNA methylation. Worms were exposed to various concentrations of 2,4-D (0–100 mg/L) at multiple time points. Nociceptive responses, such as scrunching, C-shapes, and seizures, survival, and mortality, were monitored. Photophobic behavior was tested using wavelength-specific light stimuli to determine whether 2,4-D disrupted sensory-motor processing. DNA methylation ELISA assay was performed to determine whether 2,4-D causes epigenetic changes as a molecular proxy for 2,4-D exposure. Higher concentrations of 2,4-D induced abnormal nociceptive behaviors and increased mortality. However, phototaxis assays suggest that 2,4-D does not impair phototaxis in planarians. To our knowledge, this is the first study to demonstrate concentration-dependent DNA methylation changes in Girardia dorotocephala, providing an insight into the epigenetic effects of 2,4-D exposure. In our planarian model, our findings suggest that the environmental toxicant 2,4-D affects aquatic invertebrates at both behavioral and molecular levels, further supporting the use of planarians as a sensitive model for neurotoxicity and ecotoxicology research.