الفهرس 
Part 1Only 14 pages are availabe for public view
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Abstract
present work is concerned with the effect of different coJnce,ntr·ati<ons of three heavy metals namely lead, cadmium & co]Jp{:r on the freshwater bivalve Corbicula fluminea. This indicated by assessing the survival rates after 7 days of
exposure to certain concentrations of these pollutants and determination of Lc50 for each metaL The rate of bioaccumulation of ’h & 3!. Lcso of Cd, Cu & Pb in the soft parts of the investigated specimens after one and two weeks of exposure was determined. Moreover, the histopathological changes in some internal organs (Foot, gills, digestive gland and gonads) and the mean enzyme activity of esterase in the digestive gland of this clam due to its exposure to ’h & % Lcso of Cd, Cu & Pb for one and two weeks were studied.
The results of this work indicated that the survival rate was inversely proportional to the concentrations ofPb, Cd & Cu in their test solutions. The respective values of their Lc50 after 7 days of exposure were 32, 4.5 & 8 mg/L Theorderofbioaccumulationrateof’h&% Lc50 of these heavy metals after one and two weeks was Pb > Cu > Cd.
Hisological examinations of the foot, gills, digestive gland and gonads of the treated clams revealed various degrees of histopathological changes.
Seven esterase bands were found in the digestive gland of normal animals by using gel-electrophoresis analysis. These bands were distributed according to the speed of their migration and position relative to the site of sample application. Three of these bands migrated above the sample site (anodaly bands) while the other bands migrated below the sample site (cathodaly bands), The exposure of calms to’/, & % Lc 50 of Pb, Cd & Cu for one and two weeks affected the number, intensity and migration velocity of these esterase bands....