Avaliação toxicológica em juvenis de Rhamdia quelen submetidos a diferentes concentrações do herbicida 2,4 diclorofenoxiacético

Abstract

One of the herbicides most commonly used in agriculture is 2,4 dichlorophenoxyacetic acid, its indiscriminate use has generated an increase in water pollution, causing great environmental concerns. The objective of the present study was to determine the toxicological effects of the herbicide 2,4-D in juveniles of Rhamdia quelen (jundiá). To this end, 96 specimens of Rhamdia quelen were subjected to an acute test (96h) of exposure to the 2.4 D herbicide at increasing concentrations of 0.0; 15; 30 and 45 mg / L. For each concentration, 4 replicates were made, with 6 specimens each. After 96 hours, the animals were weighed, measured and anesthetized for blood collection for hematological analysis, beingquantified: the number of erythrocytes, leukocytes, thrombocytes and monocytes. Then, the animals were euthanized and laparatomized to collect the muscles and livers for histomorphometric and biochemical analyzes. For histomorphometry, liver and muscle were isolated clean and weighed and submitted to routine histological techniques, stained and evaluated for the hepatosomatic index (IHS) and condition factor (HR). A liver fragment was used for enzymatic analysis of LPO, AChE and PT. Hematological analyzes showed that 2,4-D causes changes in the number of leukocytes, monocytes and thrombocytes, in all concentrations compared to the control group (not exposed). The mean value of erythrocytes was 1.6x106µL-1. 2,4-D did not significantly change the diameter of muscle fibers (p≤0.05), but the herbicide at concentrations of 30 and 45mg / L reduced and increased, respectively, the number of hepatocytes when compared to the control group (not exposed). The activity of hepatic OLP was not altered by 2,4-D at any concentration used. Similarly, there was no evidence of inhibition of hepatic acetylcholinesterase (AChE) activity in animals exposed to 2,4-D (p≤0.05). However, at concentrations of 30 and 45 mg/L of 2,4-D, a reduction in total protein was observed. The changes found in Rhamdia quelen exposed to 2,4-D indicate that, acutely, exposure to the herbicide mainly promotes liver and hematological damage, indicating greater vulnerability of these tissues to the herbicide in the short term. Chronic exposure is likely to increase damage and cause further changes in other tissues. The results obtained in this work will serve as subsidies for further research with toxicological tests with the herbicide 2,4-D, and will assist in the understanding of morphometric, histological, hematological and biochemical behaviors for juveniles of the species Rhamdia quelen, exposed to acute contamination by the 2,4-D herbicide.