Planarian Exposure to the Herbicide 2,4- Dichlorophenoxyacetic (2,4-D)

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 such as impaired motor function and altered neurotransmitter activity. Planarians offer a valuable system for toxicological studies due to their well-characterized nervous system, regenerative capacity, and measurable behavioral responses. This study investigates the neurotoxic effects of 2,4-D exposure in the planarian species, Girardia dorotocephala, including assessment of nociceptive behaviors, survival rate, and phototactic responses. Worms were exposed to various concentrations of 2,4-D (0–100 mg/L) over 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 disrupts sensory-motor processing. Higher concentrations of 2,4-D induced abnormal nociceptive behaviors and increased mortality. However, phototaxis assays indicate 2,4-D does not impair phototaxis in planarians. These findings will contribute to a broader understanding of how environmental toxicants affect aquatic invertebrates at both behavioral and molecular levels and reinforce using planarians as a sensitive model for neurotoxicity and ecotoxicology research.