Priyaleksmi, A (2001) Heavy metal loading and its impact on Villorita cyprinoides (Hanley) along the estuaries of south west coast of India (TH 097). PhD thesis, Central Institute of Fisheries Education, Versova.
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Bivalves which are filter feeders are found to be the best ones suited for pollution monitoring because of their abiltiy to concentrate pollutants to several orders of magnitude. For the present study, black clam, Villorita cyprilloides was selected owing to its euryhaline and hardy nature. A fortnightly study conducted at the four stations (station I, 2, 3 & 5) and a seasonal (Pre-monsoon, Monsoon & Post-monsoon) study conducted at the other four stations (station 4, 6, 7 & 8) revealed a postmonsoon maxima and a pre-monsoon minima for copper in the whole soft tissue and digestive gland of clams. Cadmium and lead values were comparatively low. However, metals in the sediment did not show any seasonal variation in accumulation. Acute toxicity and bioaccumulation studies (using copper and lead) showed that copper was more toxic to the clams than lead. Digestive glands showed highest value for copper whereas gills showed highest value for lead. A linear relationship between time and concentration was observed in the accumulation of the two metals in the tissues studied. Histology of the digestive glands and gills of copper and lead exposed clams showed severe degeneration and destruction of the epithelial cells. The planimetric study conducted also revealed destruction of epithelial cells which was indicated by a significantly lower MET(Mean Epithelial Thickness) values for copper exposed clams. There was Significant incrcasc in MLR & MLRlMET values of copper exposed clams. Though samc results were obtained for lead exposed clams the values did not show any statistical difference. Fine structure of the digestive glands of copper and lead exposed clams revealed proliferation of SER, Iysomes, destruction of digestive cells, a labile nuclear membrane and breakage at the basal lamina.
|Item Type:||Thesis (PhD)|
|Supervisor(s):||Pillai, V Kunjukrishna|
|Uncontrolled Keywords:||Heavy metal loading; Villorita cyprinoides; estuaries|
Marine Environment > Marine Pollution
Molluscan Fisheries > Clam
|Divisions:||CMFRI-Cochin > Fishery Environment|
|Deposited By:||Geetha P Mrs|
|Deposited On:||28 Jan 2011 16:43|
|Last Modified:||28 Jan 2011 16:43|
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