الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 251 |  |  |
| | | from | 251 | | |
Abstract
Heavy metals and polycyclic aromatic hydrocarbons (PAHs) pose ecotoxicological impacts on resident aquatic organisms. These pollutants bring about adverse health effects. Fish develops protective defense mechanisms against the damaging effects of heavy metals and other pollutants. This study was aimed to investigate the concentrations of certain metals (Cd, Fe, Mn, Co, and Pb) in water, sediment, and tissues of O. niloticus. This study was also aimed to assess the adaptive response of the Nile tilapia exposed to heavy metals and PAHs. The results showed water and sediment samples from the Kalabsho drainage canal contained significantly higher levels of heavy metals (Cd, Fe, Mn, Co, and Pb) and PAHs compared to those from the Nile River. The tissues of tilapia from the drainage canal also accumulated higher concentrations of heavy metals. Tilapia from the drainage canal exhibited a significant increase in serum biochemical parameters, superoxide dismutase, and malondialdehyde as well as a significant decrease in glutathione compared to those from the Nile River. Histological examination of the liver showed severe alterations in tilapia tissue. Nanomechanical properties (roughness and stiffness) confirmed the damaging effect of metals on liver tissue. Stress-related genes were significantly upregulated in the liver of tilapia from the drainage canal compared to those from the Nile River. In conclusion, the Nile tilapia has been proved a good candidate in ecotoxicological studies. The biomarker responses of the Nile tilapia effectively demonstrate the presence of xenobiotics in the aquatic habitat. The results support the utilization of molecular biomarkers of Nile tilapia as warning signals in biomonitoring of aquatic pollution. The findings provide a rational application of histological, nanomechanical, and biochemical parameters to be used as a signature of metal stress.