The distribution and behavior of mitochondria in the centric diatom Pleurosira laevis were observed using two fluorescent dyes, DAPI for mitochondrial DNA and DiOC for the mitochondrial membrane. When chloroplasts were located in the cortical cytoplasm, most of the mitochondria were evenly distributed at the interspace of the chloroplasts and a lesser number of them were in the nuclear cytoplasm. When all of the chloroplasts rapidly migrated into the nuclear cytoplasm due to an increase in light intensity, one third of the mitochondria also migrated into the nuclear cytoplasm, being dragged by the chloroplasts during this movement. Mitochondria gathered in the nuclear cytoplasm with the aggregated chloroplasts. When the chloroplasts migrated from the nuclear region to the cortical region as a result of a decrease in light intensity, the mitochondria migrated to the cortical cytoplasm again being dragged by the chloroplasts. Time-lapse video observation showed that cytoplasmic streaming and organelle movements did not take place if there were no changes of light conditions. From the observations, it was proved that the mitochondria of this diatom are not capable of moving independently but could migrate in a whole cell depending on chloroplast movement which is regulated by light conditions.
The growth characteristics and extracellular organic matter of Synedra acus Kützing, which often causes problems to the public water supply, were investigated by using an artificial culture medium. Synedra acus was removed from the water of a reservoir; the cultivations were carried out between 10-25°C with continuous light illumination, under cool-white fluorescent lamps at 4,500 lx and 2,000 lx. Under these conditions, the higher the temperature and the brighter the light became, the more rapidly the diatoms grew. With the growth of the diatoms, extracellular organic matter, which included saccharides, increased at a 40% ratio. Following the Logarithmic phase, extracellular saccharides were yielded at a ratio of 11-12% to the dry algae. The composition of these saccharides was recorded as follows: Rib + Ara: Fuc: Xyl: Man: Gal: Glu = 4.3: 1.8: 7.1: 8.6: 9.4: 68. As a result, saccharides produced by Synedra acus were characterized by a high concentration of Glu and the absence of Rha.
Attached diatom assemblages in the littoral zone of Lake Biwa were investigated in March and August,1994. The diatom assemblages in March were assemblages composed mainly of species commonly found in oligotrophic lakes. In August, Achnanthes minutissima was most abundant, but large differences were found in species composition among sites and the dominant species were site-specific. The results suggest that global environmental factors were important in determining the composition of diatom assemblages in March, while local environmental factors were more important in August.
The areolae structure of Amphitetras antediluviana Ehrenberg growing profusely on sandy sediment in Toyama Bay was observed in detail using a scanning electron microscope. We found that there are two types of areolae occlusion within one valve. Many areolae were occluded by complex cribra near their outer openings. As each pore of the cribrum bears a flap on its outer surface, externally, many circular slits were observed in the occlusion. However, the meshwork of the cribrum was apparent, internally. The other areolae were occluded by volae with distinctive slits. Each vola was somewhat raised and located on the outer opening of the areola. The slits of the volae were also evident internally. The areolae with this occlusion were not abundant but were distributed over the valve, however, they were not observed at the circular elevated area of the valve.
A gravity core from Lake Hibara (Urabandai Plateau, Fukushima Prefecture) has been investigated, and a taxonomic study of the diatoms found within the sediments is presented here. The checklist includes some species rarely reportcd from Japanese lakes, and others with recently addressed nomenclatural problems. Over a hundred recognised taxa and some unidentified forms are illustrated.
The collection of attached diatom assemblages of 14 samples and the measurement of some physicochemical variables of spring water in each sampling site were done on 4 July 1994 in 12 springs in the Ikuji area and on 2 July 1995 in a spring in Sugisawa. In this study the following results were obtained. 1. The distribution of pH valu e s ranged from 6.2 to 7.3 and EC values ranged from 79μs⋅cm-1 to 190 μs⋅cm-1. 2. DAIpo valu e s ranged from 61 to 79, indicating that the degree of water pollution at all sites corresponded to the oligosaprobic level in the former saprobic system. None of the sampling sites in the present survey showed any DAIpo value higher than 85(xenosaprobic) which is the lowest DAIpo value for the mountain springs. This assessment indicates that springs in the coastal area of the a lluvial fan of the R. Kurobe are slightly affected by organic pollutants. 3. The range of DAIpo values from 61 to 79 obtained in this survey of springs was smaller than that from 54 to 91 calculated using the samples collected from the rivers near the springs. This result suggests that the penetration of surface water into underground affects the water quality of springs.
Thalassiosira tealata Takano in Japan was first found in August 1979 at Tachibana Ura, Tokushima Prefecture, by staffs of the Nihon Kaiyoseibutsu Kenkyujo Co. Ltd. This small centric diatom has T-shaped marginal strutted processes provided with two, long, opposing wings extended from the scaphoid skirts of the processes. Its labiate process is nearly on the margin of the valve face, and 1-4 areolae are apart from the externally left-hand strutted process at the 12 O'clock position. The rows of areolae are mostly radially fasciculated. The cells are so small,6.3-9.6, tim in diameter, that an electron microscope is needed for its precise identification. This small diatom may be a common habitant in the warm coastal waters of the Pacific, like Tachibana-ura and Atsumi Bay in summer. By recent information newly sent from my friend living in England, this small diatom could be transferred by air-cargo from Japan, may be with Japanese oysters.
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