Effect of Permethrin insecticide and Paraquat herbicide on growth and population density of freshwater Rotifer (Brachionus calyciflorus)

This study evaluated the acute toxicity of herbicide paraquat and the insecticide permethrin and their impacts on growth and reproduction of freshwater rotifers Brachionus calyciflorus according to the guidelines OECD. The acute toxicity (LC50 24h) of paraquat and permethrin on freshwater rotifers B. calyciflorus were 0.541 and 8.997 mg l-1, respectively. The level of exposure responses of rotifers to four different concentrations of the pesticide paraquat (0.027, 0.054, 0.1 and 0.27 mg l-1) and permethrin (0.449, 0.899, 1.799 and 4.498 mg l-1) with three replicates per concentration was evaluated for ten days. The results showed that the specific growth rate and populations of rotifer decreased by increasing the concentration of toxins in the culture medium (p<0.05). The highest population density in response to permethrin was 56.6±1.5  in samples treated with concentration of 0.449 mg l-1. The highest population density in response to paraquat was33.3±2 in samples exposed to concentration of0.027 mg l-1). Also, the specific growth rate was 0.23 in control treatment  and zero in rotifers exposed to concentrations of 1.799 and 4.498 mg l-1 permethrin. Moreover, the specific growth rate was 0.14 in control treatment and zero in treatments exposed to concentrations of 0.1 and 0.27 mg l-1 paraquat. The results of this study showed that the toxins paraquat and permethrin are in the category of very toxic and moderate toxicity for rotifer B. calyciflorus, respectively.