BIOMARKERS IN TILAPIA (Oreochromis aureus) FROM THE EDKU LAKE (ALEXANDRIA) AS EVIDENCES FOR GENOTOXIC AND IMMUNOLOGICAL EFFECTS

Abstract

Aquatic animals have, often, been used in bioassays to monitor water quality (Carins et al., 1975; Brugs et al., 1977). The development of biological monitoring techniques based on fish offers the possibility of checking water pollution with fast responses on low concentrations of direct acting toxicants (Poele and Strick, 1975; Badr and El-Dib, 1978). Lakes Waterfall is important sinks of pollutants derived from anthropogenic activities. Fish inhabiting these areas have been proposed as bioindicator for pollu- tion monitoring through assessment of sensitive biomarkers. Biomarkers can be defined as a change in biological response, ranging from molecular through behavioral changes, which can be related to exposure or effects of environmental contaminants (Depledge et al., 1995). Biomarkers represent any biochemical and behavioral (or other) alteration that can modify the well-being of organism. Several molecular and cellular components in different fish species have been used as biomarkers for pollution exposure and effect, including biochemical, immunological and genetic parame- ters (Van der Oost et al., 2003). Fish are excellent subject for the study of various effects of contaminants present in water samples since they can metabolize, concentrate and store water borne pollutants (Elshehawi et al., 2007). Biomarkers for water pollution are early diagnostic tools for biological effect mea- surement and environmental quality as- sessment (Cajaraville et al., 2000). Tilapia is among many fish species that are used for this proposal. They represent different sensitivity for environmental pollutants. The biological effects of pollutants were measured in Edku Lake using Tilapia (Oreochromis aureus) as bioindicator samples and were examined for the activities of glutathione-S-transferase acid. Liver glutamic oxaloacetic transami- nases (GOT) and glutamic pyruvic transaminases (GPT) were used to assess the impact of long-term exposure to water borne cadmium (Cd) on C. carpio. Both showed increased activity in response to cadmium (De la Torre et al., 2000). The effect of lead and copper on certain biochemical parameters of the aquatic insect Sphaerodema urinator has also been estimated. The results showed an increase in the activity of acid phospha- tase. Also the treated insects showed lower activities of GOT and GPT (Bream, 2003). GOT and GPT were employed to estimate the effect of accumulated residues of DDT, DDE, aldrin, dieldrin and delta-methrin. Higher level of GPT and GOT was found in samples with higher accumulation of pesticide residues. This possibly indicates a correlation between exposures of Pesticide and increased level of the two enzymes (Saqib et al., 2005). This work was planned to in- vestigate if aquatic pollutants present in the Edku Lake generate biological res- ponses by comparing Tilapia aureus from this site with those collected in the non- polluted site of the north-west of the lake. To accomplish this objective, biomarkers for pollution exposure and effect re- sponses were measured in tissue samples from Tilapia aureus collected from these two regions, in winter and summer. Polychlorinated biphenyls (PCBs) as pollutants induce effects on the immune system (Smialowicz et al., 1989). This study was performed to detect pollution in Lake Waterfall.