| Popis: |
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 (LC 50 ) at 96 h, which was evaluated in 88 fish exposed to chlorpyrifos concentrations from 0.015 to 1.5 μg/L. The value established for CL 50 was 0.11 μg/L (p < 0.05). The chronic toxicity test to sublethal doses (0.5, 0.1 and 0.001 x of the LC 50 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 μg/L in 20 and 50 days, which increased in the exposed group to 0.055 μg/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 μg/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. |
