Toxicity of fipronil and atrazine on Metapenaeus affinis (Milne-Edwards, 1837) and their effects on oxygen consumption

Increasing the use of pesticides has led to declines in crustaceans in aquatic systems. In this study, the effects of acute doses of fipronil insecticides and atrazine herbicides on the toxicity in sublethal concentrations and their effect on oxygen consumption of adult Metapenaeus affinis at 20±1°C and 4 psu salinity were investigated. Series of fipronil (0.05-2 µg.l^-1) and atrazine (625-2000 µg.l^-1) lethal concentrations were used. Fipronil showed high toxicity to adult shrimp M. affinis compared to the atrazine. The median lethal concentration (LC50) for 96h of fipronil and atrazine were 0.47 and 8280.02 µg.l^-1, respectively. A decrease in the rate of oxygen consumption with increasing sublethal concentrations after 24h was observed in fipronil and atrazine exposed shrimps. A significant difference in oxygen consumption was found between the control and the experimental treatments. The oxygen consumption of high concentration of fipronil 0.2 µg.l^-1and high concentration of atrazine 6000 µg.l^-1were 0.190 and 0.373 µg.l^-1/O2/gm/h, respectively, compared to control one (0.540 µg.l^-1/O2/gm/h).