Genotoxic and HematologicalEffects Associated withChronic Dietary Mercury Toxicity in Juvenile Tilapia Oreochromis sp.

Fish farming and artisanal fishing represent important protein sources for riverside communities and populations of small towns in the Amazon. In recent decades, the Amazon basin has been the target of environmental contamination by mercury (Hg), which warns of possible adverse effects of human exposure through food. In this study, we evaluated the effect of mercury bioaccumulation in juvenile tilapia exposed via dietary intake. The fish were fed commercial feed supplemented with methylmercury chloride for a period of 28 days. Hematological parameters (hemogram, hematocrit (Hct), hemoglobin (Hgb), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC)) and genotoxic effects in blood (micronucleus (MN), erythrocytic nuclear abnormalities (ENAs), DNA damage) were analyzed. Total mercury (THg) was determined in muscle tissue and blood. Hg bioaccumulation increased 7-fold in exposed fish, representing a body accumulation rate of 41%. No variation in growth performance or feeding habits was observed. The following biomarkers Hgb, thrombocytes (Trb), MCH, MCHC, MN and ENAs showed variation as a function of exposure time. Compensatory mechanisms of defense metabolism showed greater deficiency between 21 and 28 days.