Assessment of acute toxicity of carbofuran in Macrobrachium olfersii (Wiegmann, 1836) at different temperature levels

Carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate; C12H15NO3) is one of the most toxic carbamate pesticides. For acute toxicity of carbofuran, juveniles of Macrobrachiumolfersii were exposed to different concentrations of carbofuran using the static renewal method at different temperature levels (15, 20 and 25 degrees C) at pH 7.0. The main purpose of the present study was to detect the acute toxicity of carbofuran to M.olfersii and investigate its effects on oxygen consumption and ammonium excretion; these tests have not been carried out in this species before. First, the acute toxicity - median lethal concentration - of carbofuran to M. olfersii for 24, 48, 72 and 96h was examined, which resulted in the following values: 1.64, 1.22, 0.86 and 0.42mgL(-1), respectively. Furthermore, we also found that carbofuran caused an inhibition in oxygen consumption of 60.6, 65.3 and 66.2% with respect to the control. In addition, after separate exposures to carbofuran, elevations in ammonium excretion were more than 500% with respect to the control.