Acute toxicity of organophosphate pesticide profenofos, pyrethroid pesticide λ cyhalothrin and biopesticide azadirachtin and their sublethal effects on growth and oxidative stress enzymes in benthic oligochaete worm, Tubifex tubifex.

The present study was aimed to assess the acute toxicity of organophosphate pesticide, profenofos; synthetic pyrethroid pesticide, λ cyhalothrin and biopesticide, azadirachtin and their sublethal effects on growth rate and oxidative stress biomarkers in Tubifex tubifex in vivo. The results showed that 96 h LC ₅₀ value of profenofos, λ cyhalothrin and azadirachtin to Tubifex tubifex are 0.59, 0.13 and 82.15 mg L ^-1 respectively. Pesticide treated worms showed several behavioral abnormalities including increased mucus secretion, erratic movements, wrinkling activity and decreased clumping tendency during acute exposure. The percentage of autotomy increased significantly (p < 0.05) with the increasing concentration of the pesticides at 96 h of exposure. Sublethal concentrations of profenofos (0.059 and 0.118 mg L ^-1 ), λ cyhalothrin (0.013 and 0.026 mg L ^-1 ) and azadirachtin (8.2 and 16.4 mg L ^-1 ) caused significant alterations in growth rate and oxidative stress enzymes in T. tubifex during 14 days exposure period. The growth rate of the pesticide exposed worms decreased significantly (P < 0.05) in a concentration and duration-dependent manner. Superoxide dismutase (SOD), reduced glutathione (GSH), glutathione-s-transferase (GST) and glutathione peroxidase (GPx) demonstrated a noteworthy (p < 0.05) initial induction followed by a subsequent reduction, while catalase (CAT) and malondialdehyde (MDA) exhibited noteworthy induction (p < 0.05) all through the exposure time. Through principal component analysis, correlation matrix, and integrated biomarker response, the effects of profenofos, λ cyhalothrin and azadirachtin on T. tubifex were distinguished. These results indicate that exposure to profenofos, λ cyhalothrin and azadirachtin affect survivability, change the behavioral responses, reduce the growth rate and induce oxidative stress enzymes in T. tubifex.
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