A. Gharaei - Department of Fisheries, Faculty of Natural Resources and Hamoon International Wetland Research Institute, University of Zabol, Zabol, Iran
M. Karimi - Department of Fisheries, Natural Resources Faculty, University of Zabol, Zabol, Iran
J. Mirdar Harijani - Department of Fisheries, Faculty of Natural Resources, University of Zabol, Iran
M. Miri - Hamoon International Wetland Research Institute, University of Zabol, Zabol, Iran.
C. Faggio - Department of Chemical, Biological, Pharmaceutical, and Environmental Sciences, University of Messina, Viale F. Stagno d’Alcontres, ۳۱, ۹۸۱۶۶ Messina, Italy

Rotifers due to their relatively short lifespan, high fecundity and high rate of population growth are ideal for chronic toxicity tests. The aim of this research was to determine the lethal concentrations (LC۵۰ ۲۴ h) of deltamethrin and imidaclopride and their impacts on the reproduction and growth of the freshwater rotifer, Brachionus calyciflorus. Experiments were carried out based on the guidelines of the standard methods of OECD. Based on LC۵۰ levels of pesticides, different concentration treatment groups designated and rotifer population responses in the five different concentrations of deltamethrin (۰.۰۰, ۰.۰۵, ۰.۱۰, ۰.۲۱ and ۰.۵۳ mg L-۱) and imidacloprid (۰.۰۰, ۶.۲۲, ۱۲.۴۵, ۲۴.۹۱ and ۶۲.۲۷ mg L-۱) were studied during ten days. The LC۵۰ ۲۴h of deltamethrin and imidacloprid for freshwater rotifer determined as ۱.۰۶ mg L-۱ and ۱۲۴.۵۴ mg L-۱, respectively. The density of rotifers in all treatment groups of pesticides decreased significantly compared to the control group at tenth day (p<۰.۰۵). The ratio of ovigerous females to nonovigerous females (OF/NOF) and the ratio of mictic females to amictic females (mic/amic) were significantly affected (p<۰.۰۵) in all concentrations of both insecticides. The results of this study suggested that B. calyciflorus are severely sensitive to deltamethrin rather than to imidacloprid pesticide.

Brachionus calyciflorus, Pesticide toxicity, Population growth, Lethal concentration.