Cd (2+) may cause cytotoxicity by binding to many cellular components such as DNA and proteins and by displacing metals which play important roles in metabolic reactions. The objectives of this thesis are: 1) to find out the effects of Cd on larval development of the barnacle Balanus amphitrite amphitrite which is abundant in Hong Kong; 2) to examine the cytotoxic mechanisms of Cd by analyzing the larval enzymatic system. 3) to investigate the relationship between the toxicity and accumulation. Results showed that when NII larvae were exposed to lethal concentrations of Cd, significantly fewer survived and moulted to NTII. Beyond NIII, no effect was observed on long-term survivorship of stage-specific barnacle larvae. Besides survivorship, experimental results proved that both the suble...[ Read more ]

Cd (2+) may cause cytotoxicity by binding to many cellular components such as DNA and proteins and by displacing metals which play important roles in metabolic reactions. The objectives of this thesis are: 1) to find out the effects of Cd on larval development of the barnacle Balanus amphitrite amphitrite which is abundant in Hong Kong; 2) to examine the cytotoxic mechanisms of Cd by analyzing the larval enzymatic system. 3) to investigate the relationship between the toxicity and accumulation. Results showed that when NII larvae were exposed to lethal concentrations of Cd, significantly fewer survived and moulted to NTII. Beyond NIII, no effect was observed on long-term survivorship of stage-specific barnacle larvae. Besides survivorship, experimental results proved that both the sublethal and the lethal Cd treatments did not affect the duration of development, or larval size of all the larval stages, or size of newly-settled juveniles. Adverse effects of Cd however, were reflected in enzymatic activities. AcP which is an important enzyme for growth and cell differentiation was inhibited in NII larvae after the sublethal and lethal Cd treatments for 24 hours. Nevertheless, cytotoxic effects of Cd was not indicated by any free radical stress occuring in the cell. There was insignificant lipid peroxidative damage in barnacle cellular membranes, or on free radical defence components - SOD, CAT activities except POD activities. Results of the accumulation study showed that the uptake of Cd at the initial 8hr of exposure was unregulated. However, the accumulation very soon triggered a regulatory mechanism, which was broken down after 8 hours.