Herbicides are agricultural pesticides directed at weeds control, considered the
most frequent pesticides in Brazilian fresh waters. The 2,4-D + picloram-based
herbicides are among the widely used formulations, which might promote
contamination of aquatic environments. This study evaluated the toxicological
potential of commercial herbicide 2,4-D + picloram-based (Norton®) Piaractus
brachypomus using multi-biomarkers. Median-lethal concentration (LC50-96h) was
determined and neurotoxic, cytogenotoxic, hematological, biochemical and
morphological biomarkers were used to evaluate the effects of the compound in
different tissues. The results showed that the determined LC50-96h was 1.54 g L-1
and the behavioral disorders presented include loss of reflex, muscle spasms and
opercular hyperventilation. The juveniles were exposed to a sublethal
concentration of 1.11 g L-1
in a static system for 96 hours and the observed effects
showed the inhibition of acetylcholinesterase in the muscle, indicating a
disturbance in the neuromuscular system. The haematological examinations
indicated macrocytic anemia, probably a compensatory response to maintain
adequate oxygen transport. There was no increase in micronuclei frequency,
however, the exposure promoted an increase in nuclear anomalies, suggesting
cytogenotoxic effects. The hepatotoxicity biomarkers showed inhibition of alkaline
phosphatase activity, indicating that exposure may have caused changes in the
hepatocyte membrane. Liver morphology exhibited pathologies, such as
architecture and cellular alteration, atrophy and nuclear alterations. Changes in
metabolic intermediates, in rate of plasma glucose and muscle glycogen, showed
dysfunction in carbohydrate metabolism. Lesions in the gills included constriction
of the pillar cell system and hypertrophy of the lamellar epithelium, demonstrating
physiological adjustments to preserve the functions, of which they maintained the
excretory function. In the kidneys, individual morphological lesions were
observed, such as architecture and cellular alteration, capable of causing losses
associated with the tubular resorption capacity. The biotransformation system
and lipid peroxidation indicate that the herbicide did not impair the detoxification
capacity of the antioxidant defense system and there were no elevated effects of
oxidative stress. In conclusion, the results showed that the commercial herbicide
promoted morphophysiological changes in the tissues in P. brachypomus,
demonstrating that the effects can compromise the animal's health.
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