Behavioral alterations in the earthworm Eisenia fetida after exposure of the pesticide paraquat under in vitro conditions

Since the late 1960s, soil ecotoxicology had attracted significant attention due to the extensive use of pesticides. Earthworms, as keystone species and bioindicators, were vital for maintaining soil fertility and overall ecosystem health. This study investigated the sublethal behavioral effects of the herbicide Paraquat Dichloride (24% S.L.) on adult Eisenia fetida under controlled laboratory conditions. Worms were exposed to 120 mg/kg of soil for 14 days, and behavioral parameters such as locomotion, coiling, burrowing, mucus secretion, and feeding activity were monitored. Exposure to Paraquat caused marked behavioral disturbances, including reduced locomotor activity, abnormal coiling, impaired burrowing, decreased mucus secretion, and lower feeding rates. These behavioral changes reflected neuromuscular and physiological stress, indicating that even sublethal herbicide exposure could negatively impact earthworm behavior. Such effects might have threatened soil health and ecosystem stability, highlighting the value of behavioral endpoints as sensitive biomarkers in ecotoxicological assessments.