Toxicity assessment of chlorpyrifos in red-bellied pacu fingerlings (Piaractus brachypomus)

Pesticides have become an important environmental problem due to their indiscriminate and lack of control use, which ends up affecting drastically non-target organisms, including aquatic species. The acute and chronic toxicity of chlorpyrifos was determined in fingerlings of red-bellied pacu (Piaractus brachypomus), and it was established the value of the median lethal concentration (LC50) at 96 h, which was evaluated in 88 fish exposed to chlorpyrifos concentrations from 0.015 to 1.5 mu g/L. The value established for CL50 was 0.11 mu g/L (p < 0.05). The chronic toxicity test to sublethal doses (0.5, 0.1 and 0.001 x of the LC50 dose) was performed in 60 animals per treatment plus a witness group. Animals were exposed for 50 days, followed by 50 days without exposure, to evaluate both respiratory burst activity and plasma bactericidal activity in a challenge with Aeromonas hydrophila. Lower levels of respiratory burst were found in the exposed group to 0.0011 mu g/L in 20 and 50 days, which increased in the exposed group to 0.055 mu g/L at day 90. In addition, the bactericidal activity of plasma showed a decrease until day 40 in exposed animals compared to the witness. Also, in a trial of subchronic exposure without recovery to sublethal doses of chlorpyrifos (0.011 mu g/L), lesions were found in gills, liver, kidney and brain. This study has demonstrated the high sensitivity of this species to chlorpyrifos, postulating P. brachypomus as a bioindicator of water pollution.