Toxic Effects And Its Mechanism Of Dinoflagellate Alexandrium Tamarense On Perch Lateolabrax Japonicus

The toxic effects of a PSP-producing strain of dinoflagellate Alexandrium tamarense(ATHK) on the perch Lateolabrax japonicus, a popular commercial fish in China, were studied in this thesis. The effects of the toxic algae on the ultrastructure of branchial cells of the perch after exposing to the cultures of A. tamarense(ATHK), and the hemolytic activity of A. tamarense(ATHK) on human erythrocytes, were studied at first. Then the extracted toxins prepared from A. tamarense (ATHK) cells were intraperitoneally injected into the perches in two different modes to study the impacts of toxins on the ultrastructure of different cells and enzyme activities of perches. The high dose injection was carried out only one time during the experiment, using extracted solution prepared from 1.6×105 algae cells with 0.05N acetic acid. The PSP toxicity was about 0.886μg STX Equal,and the dose injected was about 0.0118μg STX Equal/g fish (wet weight). The low dose injection was carried out multiply during the experiment, using the solution prepared from 0.16×105 cells,with the PSP toxicity about 0.0886μg STX Equal, and the dose injected was about 0.00118μg STX Equal/g fish (wet weight;) each time. The ultrastructure of liver, kidney and gill cells were observed, and the activities of the enzymes, including Na+K+-ATPase and xenobiotic-metabolizing enzymes and antioxidant enzymes, were tested to study the mechanism of the toxic effects of extracted toxins on L. japonicus.Experimental results showed that the gills of the juvenile perches exposed to the culture medium of A. tamarense(ATHK, 4 000cells/ml) for about 48 hours were significantly damaged. The most representative symptoms included tissue edema, irregular and congregated particles in mucus cells, and disintegrated mitochondria in the chloride cells. However, similar symptoms could also be observed in perches exposed to the culture medium of a non-PSP-producing strain of A. tamarense (AT-6 strain). The observation of algae cells in the gills of tested perches suggested that the mechanical injuries caused by the carapace of the algae, instead of PSP toxins, lead to the symptoms. In the hemolysis experiment using human erythrocytes, strong hemolytic activity of A. tamarense (ATHK) was found, and the hemolytic activity was...