In the present study, Clothianidin [(E) - 1-(2 - chloro-1,3 - thiazol - 5-ylmethyl) - 3-methyl - 2- nitroguanidine] (CLO) was selected as a soil pollutant and earthworm was employed as a test organism. The various responses like biochemical and detoxification process of earthworm Metaphire posthuma towards Clothianidin at lethal and sublethal doses were studied using OECD-standardized toxicological guidelines. The present study examined the toxicity of CLO to earthworms after 28 days of exposure at conc. 0, 1.5, 3, 6, 12 and 24 mg kg-1 in a soil mixture. Biochemical markers including Guaiacol peroxidase (POD), Superoxide dismutase (SOD), Catalase (CAT), Glutathione S-transferase (GST) and content of Malondialdehyde (MDA) in earthworms were measured. Acute toxicity tests revealed that CLO caused a concentration-dependent increase in mortality with LC50 (Lethal concentration) values of 10.960 and 8.201 mg kg-1 for 7th and 14th day respectively. The earthworms were exposed to CLO contaminated soil for 56 days and reflecting the significant decrease in earthworm growth, cocoon and hatchling production. Moreover, enzyme activities such as CAT, SOD, POD and MDA content were significantly enhanced with the increased concentration and exposure period of CLO. Molecular docking studies indicated that CLO primarily interacts to the junction site of SOD and in active centres of CAT, POD and GST. As a result, the current findings imply that the sub chronic CLO exposure can induce variations in physiology and avoidance behaviour of earthworms, oxidative stress as well as alterations in enzyme activities.
Keywords: Clothianidin; Earthworms; Metaphire posthuma; Neonicotionoids; Oxidative stress.
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