Hematological and histopathological analysis in Nile tilapia, exposed to sublethal concentrations of sodium selenite (Na2SeO3 Se4+)

Abstract

The aim of this study was to analyze the effects of chronic toxicity of sodium selenite (Na₂SeO₃ SE₄⁺) on juvenile Nile tilapia, Oreochromis niloticus. Therefore, a toxicity test was carried out with three sub-lethal concentrations of that salt (0.4 mgSe L^-1, 0.04 mgSe L^-1 and 0.01 mgSe L^-1), plus a control group. The experiment was carried out for 14 days, sampling six individuals per treatment in intervals of 0, 3, 7, 10 and 14 days. Effects of chronic sub-lethal concentrations of selenite were evaluated by routine hematological and histopathological analysis. There were significant differences (P<0.05) in the rate of hemoglobin, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC) and an increase of the total number of leukocytes, mainly due to the increased number of lymphocytes, monocytes, and neutrophils. Severe gill hyperplasia was found on the fourteenth day. Nephrosis were observed in the cephalic kidney, characterized by glomerulonephritis and tubular vacuolar degeneration, which was a result of the necrosis or secondary infection, glomerular atrophy and glomerulosclerosis, proliferative glomerulonephritis, nephrosis, nephrosclerosis, tubular calcification, edema and hemorrhage. It was found that selenite at the tested concentrations, despite being sub-lethal, caused histological and hematological changes in Nile tilapia.