Physiological, morphological and ecological studies on the multiplication of red tide organisms

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1)Taxonomical studies : We have clarified the taxonomic confusions as follows: a) the algae described under the name of Olisthodiscus luteus by many phocologists is identical to H. akashiwo. b) Fibrocapsa japonica must be treated with an autonomous genus separated from Chattonella.2)Cell division and chloroplast replication : The cell division and chloroplast replication in Heterosigma akashiwo occurred as separate synchronous events during the cell cycle, when the cells were subjected to light-dark regimes. The synchronization index of cell division in cells cultured under a 12h L/12h D was calculted to be 0.79 - 0.83, indicating the better synchronization. These results indicated that H. akashiwo cells are an excellent material for the analysis of various biological events. Changes in fine structures accompanying with the cell division and chloroplast replication were observed using electrom microscope.3) Diurnal vertical migration behavior : H. akashiwo cells clearly showed diurnal … More vertical migration. The upward migration commenced a few hours before the light turned on and the downward migration a few hours before it was turned off. The diurnal verical migration behavior was closely correlated with diurnal changes in the specific gravity of the cells and/or the accumulation of neutral fat on the side of the nucleus away from the flagellar bases. This behavior was also correlated with the nitrogen metabolism, the upward migration being lost under nitrogen starvation. These results indicated that H. akashiwo cells are an excellent material fot eht analysis of cell behaviors.4) Carbon and nitrogen metabolism : The rate of photosynthetic <CO_2> fixation in H. akashiwo was not inhibited by higher light intensities, The oxygen inhibition of photosynthesis was very small. Photosynthetic <CO_2> fixation in this algal cell was mainly carried out through the reductive pentose phosphate cycle and <beta> -1,3-glucan was the major storage product of photosynthesis. The diurnal variations in nitrate reductase activity were found, if the cells were cultured in N-rich medium, whereas such variations could not be detected in cells cultured in N-starved medium. The pattern of variation was well correlated with that of the diurnal vertical migration behavior. Less