DIVERSITY OF THE VALVE ONTOGENY IN DIATOMS AND ITS RELATIONSHIP TO THE PHYLOGENY

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Marine and freshwater diatoms were collected from various places in Japan. They were isolated and cultured for the materials of morphological observations and molecular experiments. SEM observations of mature valves revealed some new structures in several species. In Cocconeis the forming valves and the developing perizonium of auxospore. The valve ontogeny of Eunotiashowed some similarity to araphid pennate diatoms in the middle stage of the development. But it showed ontogenetic similarity to biraphid diatoms in the late stages. Use of a fluorescent-label agent, which was taken into the forming valve, could distinguished the newly formed valves after nucleic division and valves already formed before nucleic division. The analyzes of 18S rDNA newly showed the phylogenetic position of Pseudostaurosira, Pseudohimantidium, Berkeleya, Diploneis, Luticola, three Cylindrofheca specis and Nitzschia palea. Close relationship between Pseudohimanthidium and Eunotia, that had been pointed out based on morphology, was not shown in the phylogenetic trees, as Pseudohimantidium formed monophyly with other araphid marine genera. Except for the relationship between Bacillariaceae and Eunotiaceae, which is an opportunist according to the number of OUT and the methods of phylogenetic analyzes, the branching order of the higher rank of diatom taxa reflected that of the ontogenetic similarities from the early to middle stages of the taxa. Sill-like DNA sequences decided in five diatoms showed the high similarity among them, impling its possibility to become a probe for exploring the origin of the biosilica mineralization ability.