Assessing acute toxicity, physiological and behavioral indicators in Nile Tilapia (Oreochromis niloticus) fingerlings exposed to dichlorvos pesticide as environmental biomarkers
2025
Davies, Chris Ibienebo | Anyanwu, Emeka Donald | Olumati, Doris Chibanya
Abuse of pesticides is increasingly becoming of a global issue, due to frequent and unregulated applications to boost agricultural productivity; to the detriment of the environment and biota.The purpose of the study was to evaluate the toxicity, behavioural and physiological responses of Nile tilapia (Oreochromis niloticus) to Dichlorvos pesticide exposure using biomarkers. A range-finding test identified the lethal concentration (LC50) over 96 hours, and a definitive test was conducted at concentrations below LC50 (0.25, 0.75, 1.0, 1.5, 2.0 ml/L and 0 ml/L) with 0.00 ml/L as the control. Mortality rates increased with time and concentration, ranging from 1–6 at 0.25 ml/L to 5–10 at 2.0 ml/L over 96 hours. The 96-hour LC50 was 0.180 ml/L, with lower and upper boundaries of 0.094 and 0.343 ml/L, respectively, and the lethal time (LT50) was 64 hours. Physiological stress indicators, including operculum beat frequency (OBF) and tail beat frequency (TBF), rose with concentration, peaking at 56.0 and 51.3 at 2.0 ml/L. Behavioral changes, such as erratic swimming, gasping for air, and discoloration, intensified with increasing Dichlorvos levels, reflecting acute stress. Water parameters fluctuated significantly and could have contributed to the observed effects. These results highlight Dichlorvos' severe impact on fish health, evidenced by increased mortality, physiological stress, and behavioral changes. Findings underscore the importance of regulating pesticide levels to protect aquatic ecosystems, with LC50 and LT50 values providing critical data for ecological risk assessments.
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