Background: Herbicides are usually used to control weeds and some of them like glyphosate are nonsele ctive herbicides. Aquatic environments are usually the last destinations of agricultural pesticides, which disrupt the metabolic processes of organisms. Thus, the aim of this study was to evaluate acute
toxicity of glyphosate on the survival rate of common carp, Cyprinus carpio.
Methods: A total of 135 common carp averaged 7 ± 0.8 g in weight were exposed to 0, 25, 50, 75, 100,125 , 150, 175 and 200 mL.L-1 glyphosate (15 fish in each treatment, with triplicates) for 96 hours. Theaquariums capacity was 98 L in volume (80 × 35 × 35 cm) and physicochemical parameters were the
same for all groups (pH 7.4-8, temperature = 26 ± 1ºC, DO = 7 mg.L-1 and total hardness of 190 mg CaCO3). LC10, LC20, LC30, LC40, LC50, LC60, LC70, LC80, LC90 and LC95 of glyphosate were calculated at 24,48, 72 and 96 hours after adding glyphosate using probit test.
Results: Mortality was observed in all treatments which exposed to higher than 50 mL.L-1 after 96 hours. The results showed that 96-hour LC50 of glyphosate for common carp was 92.71 mL.L-1. Thefish exposed to different concentrations of glyphosate showed clinical signs such as increased mucus
secretion, skin darkening and death with mouth open.
Conclusion: Glyphosate disrupts the synthesis of amino acids in plants by inhibiting enzymatic activity of 5-enolpyruvylshikimate-3-phosphate synthase (EPSP). This enzyme is absent in animals. However,glyphosate is toxic for common carp.