Parâmetros hematológicos e características histológicas em brânquia, fígado e rim de tilápia Oreochromis niloticus expostos a lambda-cialotrina

Abstract

Fish farming has been growing at great strides in the country, and linked to this development, new alternatives and resources are introduced with the objective of reducing costs and improving the zootechnical performance of the animals. One of the common managements in intensive systems is the application of pesticides as chemotherapy treatment for the control of fish ectoparasites, however, there is little knowledge about the toxic effects in the aquatic environment and mainly in fish destined for consumption. In this context, the present study evaluated the osmoregulatory responses, the enzymatic profile and histological alterations in the gill, liver and kidney of Oreochromis niloticus exposed to the insecticide Lambda-cyhalothrin (LCT), at a concentration of 1.24 μg L-1, in acute and chronic periods. The mean serum values for Na2+, K+, Cl-, Ca2+, pH, lactate, H+, HCO3, and glucose along to degree of tissue change (DTC) at 24, 96, 168, and 240 h post-exposure (hpe) were evaluated. Lambda-cyhalothrin affected the neuronal motor function at 24 hpe, followed by the increase of the K+, Ca2+, H+, and glucose levels in the exposed group, compared to the control group. Lactate and H+ levels in the exposed group were higher than those in the control group at 168 and 240 hpe respectively. HCO3, and Cl- levels increased at 240 hpe, although there was no change in the pH values. DTC was higher in treated fish than in control fish, but there were no significant differences among time-exposure, in the first article. And later, new tilapias (n=30) were subjected to three exposure periods: 72, 168 and 336 hpe (post-exposure hours) and 30 specimens exposed were separated for recovery, in order to verify the sublethal effect of the product on each treatment and the recovery capacity. For evaluation of the enzymatic profile, was analyzed the enzymes aspartate transferase (AST), alanine transferase (ALT) and gamma glutamyl transferase (GGT), and histological findings were classified according to the severity and intensity of lesions through DTC (degree of tissue change). There was a reduction in serum AST levels, on the other hand, ALT values increased with the exposure time at 72h. The GGT, despite increasing in the period of 168 hpe, there was no significant difference between the control, exposed and recovery groups (P<0.05). After the assays, the fishes presented important severe tissue. In the liver, changes were observed diffuse degeneration in hepatocytes, lipofuscin accumulation and necrosis; in the gills, complete lamellar fusion, epithelial rupture and epithelial cell necrosis; in the kidney, were enlisted tubular degenerative processes, hyaline inclusions and tubular hypertrophy in cells of kidney samples. Histological analysis revealed alterations in all tissues studied, indicating toxic effects on tilapia exposed to sub-lethal concentrations of LCT. The findings demonstrated a direct correlation between exposure to cyhalothrin and observed disturbances in blood and tissues.