الفهرس 
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Abstract
The costal Delta lakes are among the most productive natural systems in Egypt. The current configuration of these lakes is changing rapidly, due to increases in urbanization, industrialization and socioeconomic activities. In Egypt, aquatic insects have been neglected in most studies dealing with environmental toxicants. Insects are members of different levels of the food chain and may be important agents of chemical compounds entry into the chain. The present study aimed to evaluate the possible hazards resulting from water pollution on the aquatic insect Anacaena globulus, along the littoral zones of some northern Delta lakes of Egypt (Lake Mariut as polluted site and Lake Edku as reference site) which vary considerably in levels of Pollution.
Heavy metals contamination in water and sediment is one of the largest threats to environmental and human health. They occur in the environment both as a result of natural processes and as pollutants from human activities. The contamination of sediments, water resources, and biota by heavy metals is of major concern due to their toxicity, persistence and bioaccumulation problems. Aquatic insects are capable of concentrating metals, so this study tries to use the aquatic beetle Anacaena globulus as sensitive bio-indicator for investigation of the environmental pollution.
Beetles were mentioned in the present study for their highly adaptive characters for external environmental conditions and have advantage than other insects because they maintain stable populations and are long –lived. A number of essential parameters were carried out to achieve the purpose of this study including the followings:
1-Chemical studies:
A-Heavy Metal analysis:
In the current study, it was found that mean concentration of heavy metals (Fe, Cu, Pb, Cd, Co, Mn & Zn) in the water from Lake Mariut were higher than those in the water from Lake Edku this may regard to the high pollution in Lake Mariut.
B- Physico-chemical characteristics of water samples:
Pollution by heavy metals in the present study was found to cause changes in water characteristics leading to great alteration in its physiochemical parameters. Values of pH were generally on the alkaline side in the two sites being 7.4 and 7.2 in Lake Edku and Mariut, respectively. Water samples collected from lake Mariut revealed significant (p<0.05) higher concentrations of total dissolved salts (TDS), chemical oxygen demand (COD), biological oxygen demand (BOD), dissolved oxygen (DO) and alkalinity as compared to those of Lake Edku. Moreover, the data obtained from chermical analysis of water samples collected from lake Mariut revealed a significant increase (p<0.05) in the concentration of nutrient salts (phosphate, nitrate, amonia and nitrite) as compared to those of lake Edku.
2- Bioaccumulation of metals in whole body of insects:
In the present study, the results demonstrated that the mean concentration of heavy metals (Cu, Zn, Cd, Fe, Mn, Pb, & Co) in Anacaena globulus sampled from Lake Mariut were higher than those of insect tissues sampled from Lake Edku this may be due to the higher potential of tissue insects in the polluted site for bioaccumulation of these elements.
3- Biochemical studies:
The present study used a set of biomarkers to assess the state of health of the aquatic insect A. globulus in the inspected locations. According to the biochemical results in insect tissue showed significant variations in response to pollution. Several biochemical parameters decreased significantly as compared with the reference ones such as total protein content, glutathione (GSH) content, glutathione peroxidase (GPx) activity and catalase (CAT) activity. However, some other parameters increased significantly in response to pollution such as malondialdehyde (MDA) concentration, aspartate transaminase (AST) activity and alanine transaminase (ALT) activity.
The present study focused on the analysis of some antioxidant and oxidative biomarkers in addition to certain biochemical parameters. It could be concluded that exposure to pollutants (heavy metals) could cause an imbalance of prooxidant/antioxidant status in beetles. Beetles inhabiting contaminated areas might adapt to pollution by developing more effective methods for bio-elimination of pollutants. They could also develop defense mechanisms against prooxidants representing in variation of enzymatic activities and protein content.
4- Cytogenetic study:
Chromosomal aberrations:
Analysis of chromosomal abnormalities in Anacaena globulus cells showed that several types of aberrations were observed such as fragments, stickiness, gaps and polyploidy. Binucleated and micronucleus cells were also observed in the insect cells of the polluted sites. Total percent of aberrant metaphases for Anacaena globulus ranged from 7.0% in the reference to 64.0% in the polluted site, giving evidence that the analysis of insect chromosomes can easily be employed as a sensitive monitor for aquatic pollution.
The obtained results confirmed that living organisms are very sensitive to hazardous substances especially the environmental heavy metal pollutants. One of these organisms is the insects which representing herein by the diving hydrophilidae beetles, Anacaena globulus. It could be considered as a good bioindicator for environmental pollution and the studied parameters can be easily employed as sensitive monitors for the different environmental pollutants. Generally, it appears that heavy metals are capable in inducing DNA damage in insects by its observed chromosomal aberrations in germinal cells of the insect. Such results can reflect the possible mutagenicity.
It could be concluded that the hydrophilid beetle Anacaena globulus is severely affected by environment water pollutants and this is very important because of its valuable position in the food chain. The pollution impact on the insect is an obvious on the change of biochemical processes and cytogenetic constituent’s aberrant.
The beetle Anacaena globulus is a wide ranging species in aquatic habitats that is frequently exposed to pollutants in its native habitats and which therefore may serve as convenient monitor of hazards to aquatic life.
Finally, the present study tried successfully to achieve the aim of this study. It could be concluded that environmental pollutants represented by heavy metals could be considered as an important factor to cause significant alternations in many physiochemical parameters of water, biochemical and chromosomal parameters of living organisms such as insects.