Effect of Mercury Contaminated Diet on Hematology and Histology of Liver, Kidney and Gills in Nile Tilapia (Oreochromis Niloticus)

Abstract

The present study was designed to assess the impact of mercury contaminated diets on hematological parameters and histopathological alterations in vital organs of Nile tilapia. Nile tilapia is a widely cultivated freshwater species known for its rapid growth and high adaptability; however, its exposure to toxic heavy metals, especially mercury, can lead to significant physiological and structural damage. A total of 300 healthy fingerlings were randomly assigned to four treatment groups: T0 (control), T1 (0.5 mg/kg methylmercury), T2 (5 mg/kg), and T3 (10 mg/kg), with three replicates each. The feeding trial was conducted over a period of 105 days under controlled laboratory conditions. Water quality parameters were regularly monitored to assess the environmental impact of mercury exposure. In T3, significant increases were observed in ammonia, nitrite, phosphorus and iron indicating a deterioration in water quality and increased metabolic stress on the fish. Hematological parameters showed pronounced dose-dependent alterations. Hemoglobin levels declined significantly along with reductions in RBC count, mean corpuscular volume and mean corpuscular hemoglobin concentration. White blood cell counts were suppressed showing immune suppression induced by mercury toxicity. it is concluded that Mercury severely affected hematological and physiological organ system. Its contamination resulted in significant alterations in hematological parameters, including anemia and immune dysfunction, alongside severe histopathological damage in key organs such as the liver, kidneys, and gills. it is suggested to implement and enforce strict environmental policies to limit industrial and agricultural mercury discharge into water bodies.

Keywords; Nile tilapia, heavy metals, methylmercury, water quality, immune suppression, anemia