ORIGINAL ABSTRACT

INTRODUCTION: Geometric aquaculture growth has resulted in exponentially increasing use of agrochemicals as either parasiticides or herbicides in the aquaculture environment. This study determines some of the toxicological (haematological and biochemical) effects of glyphosate-based herbicides on non-target aquatic animals using Clarias gariepinus as the animal model. METHOD: Seventy-five apparently healthy adult C. gariepinus (300 g) were sourced from a local farmer and acclimatised for 2 weeks; of these, sixty subjects were divided into four treatment groups (fifteen fish per group and five replicates per unit) by simple randomisation and labelled as T0 (control), T1 (first treatment), T2 (second treatment), and T3 (third treatment). The treatments were replicated thrice. Four concentrations of Force up® [0 mL, 0.15 mL (0.003 mL/L or 5.1 mg/L), 0.225 mL (0.0045 mL/L or 7.65 mg/L), and 0.3 mL (0.006 mL/L or 10.2 mg/L) were added to a 50-L tank of water for T0, T1, T2, and T3, respectively. Approximately 5 mL of blood was collected from the fish in each treatment group 96 h post-exposure for measurement of the blood parameters and biochemical indices using standard analytical methods as well as calculation of the mean values. RESULT: The mean values of the packed cell volume, haemoglobin concentration, red blood cell count, and white blood cell count compared to the control group showed an initial increase at T1 but decreased as the glyphosate concentrations increased at T2 (0.0045 mL/L) and T3 (0.006 mL/L). The platelet mean values decreased at T1, increased at T2, and decreased at T3, while the mean values of the corpuscular volume, corpuscular haemoglobin, and corpuscular haemoglobin concentration increased with glyphosate concentration, with the mean corpuscular haemoglobin concentration decreasing at T2. Only the platelet value was statistically significant at a p-value of <0.05 using ANOVA and post hoc Tukey test. The biochemical indices showed decreases in the mean values of aspartate transaminase, blood urea nitrogen, creatinine, and triglycerides at T1, increases at T2, and decreases at T3, while the total protein (g/dL), cholesterol, alanine transaminase, and alkaline phosphatase values showed increases at T1 and decreases at T2 and T3. All these values were not statistically significant based on ANOVA and had p-values >0.05. DISCUSSION: Based on the results of this study, it is deduced that glyphosate-based herbicide (Force up®) has genotoxic, hepatotoxic, and nephrotoxic effects on C. gariepinus even at sublethal doses, with more adverse effects at increasing concentrations.