Biomarkers of Exposure and Effect in Nile Tilapia (Oreochromis niloticus) Environmentally Exposed to Multiple Stressors in Egypt.

Chemical pollution poses adverse effects on aquatic organisms, including altered gene expression. This study, therefore, investigated the hepatic expression of biomarkers of exposure and effect in Oreochromis niloticus inhabiting the drainage canal of a sugarbeet factory (an industrially polluted habitat) and the Nile River (a reference habitat). Compared to the Nile River, the drainage canal contained significantly elevated levels of heavy metals (Cd, Fe, Mn, Co, and Pb), nitrate, ammonia, nitrite, chemical oxygen demand, and biological oxygen demand. The liver of O. niloticus from the drainage canal accumulated significantly higher concentrations of the heavy metals. O. niloticus from the drainage canal had significantly higher hepatic expressions of genes related to oxidative stress (GSTa, GPx, and NRF2), metal toxicity (MT), endocrine disruption (Vtg), and hypoxia (HIF1a) and a significantly lower hepatic expression of the apoptosis-associated CAS gene. CYP1A (a detoxification biomarker) expression did not exhibit significant differences. These results provide insights into complex adaptive responses of O. niloticus to multiple chemicals and support the utilization of molecular biomarkers as warning signals for water pollution.

Influence of the Linear Alkylbenzene Sulfonate (LAS) on hematological and biochemical parameters of Nile Tilapia, Oreochromis niloticus.

The acute toxicity of household detergent (Ariel) on blood parameters and histology of Oreochromis niloticus was investigated using static bioassay for 96 h. Linear alkyl benzene sulfonate (LAS) is an anionic surfactant widely used in detergents and cleaners, both in industrial and household applications. LAS contaminating aquatic ecosystems as a potential toxic pollutant, was investigated in the present study for acute toxicity. The fish samples were divided into six groups, including 20 fish in each group. Normal feed was given to control group without detergents treatment. Hematological parameters (RBC count, Hb, Ht and platelets) were significantly declined, while WBC count showed a highly significant increase. Compared with the control group, significant elevation of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) was recorded in fish treated with different concentrations of detergent. Catalase (CAT), Superoxide dismutase (SOD) activities and Reduced Glutathione (GSH) concentration showed a highly significant reduction. Total proteins showed significant decrease, while total lipids, cholesterol and triglycerides significantly increased. The mean lethal concentration (LC50) for 96 h of Ariel was at concentration 10 mg/L. Relative percentage of detergent residues in fish muscles was increased with higher detergent concentrations. In conclusion, exposure to detergents resulted in great alterations in the histological structure of liver and gills.