The ecotoxicological study of any pesticide used in the environment is fundamental to
the regulatory process and classification as to environmental risk potential. In the
aquatic environment, agrochemicals can alter the physico-chemical variables of the
water or be toxic to biota, and may interfere with the essential functions of this
ecosystem through the reduction of species diversity. Paraquat is used for the control
of terrestrial weeds and its presence is reported in many sources of water in the
world, being widely used in Brazilian agriculture. Thus, investigating the toxicity of
this herbicide in native fish, using toxicity tests, is important to evaluate the possible
damages that the xenobiotic can cause. The objective of this work was to evaluate
the effect of exposure of tambaqui to the herbicide paraquat for 96 hours
(determining CL50-96H), genotoxic potential, hematological and biochemical
parameters, histological integrity of the gill, liver and kidney in the concentrations:
control, 10 mg L-1
, 15 mg.L-1
, 20 mg.L-1 and 25 mg.L-1
, and at 7 and 15 days without
exposure to paraquat (control, 10 mg.L-1
, 15 mg.L -1
). The herbicide caused
genotoxicity (frequency of micronuclei and nuclear abnormalities) in exposed animals
for 96 hours and in recoveries for 7 and 15 days. It was observed that the herbicide
caused several histological damages in the gills (aneurysm), and it was observed that
the herbicide did not reverse the damage caused by the herbicide. edema, cellular
hypertrophy, hyperplasia), liver (cellular hypertrophy, nuclear degeneration, biliary
stagnation, among others) and kidney (tubular lumen enlargement, tubular
degeneration, tubular lumen obstruction) of exposed animals for 96 hours, and even
after these changes remain.
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