B-esterases and Behavioral Biomarkers in Tadpoles Exposed to Pesticide Pyrethroid-TRISADA®

Abstract

Objective: The ecotoxic effects of pesticide used for mosquito’s control TRISADA ® (TRI) [deltamethrin (D) 1%+tetramethrin (T) 0.33%, and piperonyl butoxide (PB) 0.29%] on amphibian larvae were investigated. Methods: In the laboratory, Rhinella arenarum tadpoles were exposed to nominal concentrations of 0.0000 (control; CO), 0.0003125% (C1); 0.000625% (C2); 0.00125% (C3); 0.0025% (C4); 0.005% (C5) (v/v) of formulated TRI. Median lethal concentration (LC 50 ) (%) and 95% confidence limits (CL), the no-observedeffect concentration (NOEC), and the lowest-observedeffect concentration (LOEC) were quantified. The possible effects of TRI on B-esterases, evaluated through acetylcholinesterase (AChE) and carboxylesterase (CbE) activities, in addition to swimming performance (distance moved, mean speed, maximum speed, global activity, and resting time or immobility) were measured in tadpoles whose concentrations displayed survival rates higher than 50%. Results: The 48 h LC 50 of TRI was 0.00125% (v/v) [12.5 (D)+4.1 (T)+3.6 (PB); μg L -1 ] (CL: 0.000811- 0.001926%). The 48 h NOEC and LOEC values were 0.0003125% (v/v) [3.1 (D)+1 (T)+0.9 (PB); μg L -1 ] and 0.000625% (v/v) [6.2 (D) +2 (T) +1.8 (PB); μg L -1 ], respectively. At 48 h of exposure to upper sublethal TRI concentration assay (C3), AChE and CbE activities were significantly inhibited (68 and 84%, respectively) with respect to controls. Also, all the sublethal TRI concentrations caused significantly alterations of all swimming endpoints evaluated. Conclusion: The current study established that pesticide TRI is toxic to R. arenarum tadpoles and had detrimental effects on the B-sterases activities and swimming activity at TRI sublethal concentrations.