Journal of Environmental Biology

Histopathological, enzymatic and behavioural toxicity of Difenoconazole in a fresh water fish, Pethia conchonius from River Teesta

A. Ray1, D. Dutta1, J. Nag2 and M. Bahadur1*     

¹Genetics and Molecular Biology Laboratory, Department of Zoology, University of North Bengal, Darjeeling-734 013, India

²Wildlife Section, Zoological Survey of India, Kolkata-700 053, India

Received: 06 March 2025                   Revised: 29 April 2025                   Accepted: 01 July 2025

*Corresponding Author Email : min.b@rediffmail.com                  *ORCiD: https://orcid.org/0000-0002-7821-6114

Abstract

Aim: The effects of Difenoconazole fungicide were assessed on Pethia conchonius (Hamilton, 1882) by examining their behavioural, histopathological and brain acetylcholinesterase activity.

Methodology: Acute toxicity test was carried out following the OECD Guideline (2019) to estimate the 96 hr-LC₅₀ of Difenoconazole (1.886 mg l^-1). Three concentrations of Difenoconazole, (0.037, 0.188 and 0.377 mg l^-1) designated as SLC I, II and III were used to expose the fish for 96 hr. Behaviour was monitored regularly. Brain tissue was collected at 24 hr intervals for histopathological study and biochemical assay of acetylcholinesterase. Temperature, pH, total alkalinity, total hardness, and dissolved oxygen of test water, were also analyzed following the standard method.

Results: Exposed fish exhibited significantly reduced acetylcholinesterase activity and mild to severe behavioural changes including sluggish movement, loss of equilibrium, bottom-crowding and excessive mucus secretion in a dose and time-dependent response. Necrosis, vacuolation and layer detachment were also noted in the optic tectum of brain.

Interpretation: Inhibition of acetylcholinesterase activity, severe neural damage and behavioural modulations strongly highlighted Difenoconazole's neurotoxic potential.

Key words: Biomarker, Difenoconazole, Neurotoxicity, Pethia conchonius, Triazole

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