Humitake Seki

Close phylogenetic relationship between vestimentifera (tube worms) and annelida revealed by the amino acid sequence of elongation factor-lα

To clarify the phylogenetic position of Vestimentifera (tube worms), 346-bp fragments of the elongation factor-lα (EF-lα) gene (939–1286 according to the numbering of the human gene) of a vestimentiferan, Lamellibrachia sp., a sternaspid polychaete, Sternaspis scutata, an earthworm, Pheretima sp., and a gastropod, Alviniconcha hessleri, were sequenced. From the amino acid sequences of these EF-lα, and those of two other vertebrates and two arthropods, phylogenetic relationships were deduced by the maximum likelihood (ML) method, by which the phylogenetic tree can be inferred without assuming constancy of the molecular evolutionary rate. For the ML tree and all of seven alternative trees, whose log-likelihoods could not be discriminated from that of the ML tree by the criterion of the standard error, the vestimentiferan, the polychaete, and the oligochaete formed a clade, excluding the arthropods and the gastropod as outgroups. This result is convincing evidence that Vestimentifera are protostomes that are closely related to Annelida. The ML tree suggests that Vestimentifera are more closely related to Polychaeta than to Oligochaeta, though the data were not sufficient to discriminate these three groups at a significant level. From recent evidence such as morphological characteristics and molecular information, it may safely be said that vestimentiferans should be included in the Annelida provided this phylum contains polychaetes and oligochaetes.

Hobikiami Sail Trawling in Japan

Abstract Sail trawling of Hobikiami fishing consists of a boat drifting sideways downwind while towing a net. This picturesque fishing method was invented about 100 years ago as a means to reduce the then labor-intensive methods. Hobikiami trawling is analogous to flying a kite wherein kite, tail of kite, and man correspond to sail, boat, and net respectively. This technique while undergoing many modifications has remained endemic to its area of origin, Lake Kasumigaura and nearby Lake Kitaura, central Japan, because of particular requirements of the wind. The wind must be approximately parallel to the long axis of the lake, and of moderate strength and frequency during the fishing season from July through December. Diesel trawlers, which are largely independent of the weather, have replaced Hobikiami fishing on Lake Kasumigaura. Today, Hobikiami fishing is maintained on a small scale on Lake Kitaura. It is carried out by parttime fishermen-farmers who live beside the lake. Unless Hobikiami fishing can be...

Abundance and growth rate of bacterioplankton community in hydrothermal vent plumes of the North Fiji Basin

Abstract Microbiological investigation at the spreading center of the rift system of the North Fiji Basin showed a population density of bacterioplankters in the order of 103 cells ml−1, either in plumes of hydrothermal vents or immediately above; about half of these populations were composed of ultramicrocells. Other cells of the bacterioplankton communities were mostly rods in dividing stages. About 20% of the total growing bacterial cells (direct counts) were chemosynthetic (viable counts) in the plumes, whereas more than 99.9%were heterotrophic in the layers immediately above the plumes. The dividing bacterial populations in the plumes were made up of both psychrophiles and mesophiles, and their in situ generation times were estimated to be a few hours to a few days by the frequency of dividing cells method.

Phytoestrogens genistein and daidzin enhance the acetylcholinesterase activity of the rat pheochromocytoma cell line PC12 by binding to the estrogen receptor

Some compounds derived from plants have been known to possess estrogenic properties and can thus alter the physiology of higher organisms. Genistein and daidzin are examples of these phytoestrogens, which have recently been the subject of extensive research. In this study, genistein and daidzin were found to enhance the acetylcholinesterase (AChE) activity of the rat neuronal cell line PC12 at concentrations as low as 0.08 μM by binding to the estrogen receptor (ER). Results have shown that this enhancement was effectively blocked by the known estrogen receptor antagonist tamoxifen, indicating the involvement of the ER in AChE induction. That genistein and daidzin are estrogenic were confirmed in a cell proliferation assay using the human breast cancer cell line MCF7. This proliferation was also blocked by tamoxifen, again indicating the involvement of the ER. On the other hand, incubating the PC12 cells in increasing concentrations of 17 β-estradiol (E2) did not lead to enhanced AChE activity, even in the presence of genistein or daidzin. This suggests that mere binding of an estrogenic compound to the ER does not necessarily lead to enhanced AChE activity. Moreover, the effect of the phytoestrogens on AChE activity cannot be expressed in the presence of E2 since they either could not compete with the natural ligand in binding to the ER or that E2 down-regulates its own receptor. This study clearly suggests that genistein and daidzin enhance AChE activityin PC12 cells by binding to the ER; however, the actual mechanism of enhancement is not known.

Dynamics of dissolved oxygen during algal bloom in Lake Kasumigaura, Japan

Abstract Dynamics of dissolved oxygen during an algal bloom were studied in Lake Kasumigaura. Great amounts of oxygen arose from photosynthesis, and the concentration of dissolved oxygen reached 190% of saturation at 12 h. The majority of the dissolved oxygen produced was liberated into the atmosphere or consumed by microorganisms. Only minor fractions were transported into the dysphotic zone due to the low eddy diffusion coefficient in deeper waters of the euphotic zone.

Abundance and productivity of bacterioplankton in a eutrophication gradient of Shimoda Bay

Abundance, specific growth rate, and productivity of bacterioplankton were investigated over a year in Shimoda Bay, Japan, with reference to the eutrophication parameters such as dissolved organic carbon (DOC) concentration. The results from six stations in the bay indicated the formation of a eutrophic gradient ranging from eutrophic (at a river mouth) to mesotrophic (at the bay mouth) levels. Both DOC concentration and UV absorbance were found to have good correlations to bacterioplankton abundance and productivity within the eutrophication range of Shimoda Bay.

Microbial populations of hydrothermal fluid and plumes in the North Fiji Basin with reference to chemosynthesis

Abstract Bacterioplankton abundance of the hydrothermal plumes in the North Fiji Basin (NFB) was anomalously high in bottom waters at several sampling stations. Good correlation between the manganese concentration and the bacterial viable counts was found for the bottommost waters. Sulfur bacterial strains, supposedly major chemosynthetic microorganisms associated with hydrothermal activity, were isolated from the bottommost water. The bacterial population growth and the CO2-uptake by the sulfur bacterial strains suggested the sulfur bacteria in the plumes were facultatively autotrophic. Also, a sulfur bacterial strain from the hydrothermal fluid was shown to be thermophilic-eurybaric. Biogeochemical roles of the planktonic sulfur bacteria in the hydrothermal area were pointed out as: (1) a food source to filter-feeders of the vent fauna; and (2) a possible first settler of the hydrothermal ecosystems.

Ecological adaptation and acclimatization of natural freshwater phytoplankters with a nutrient gradient

Ecological adaptation and acclimatization of natural phytoplankters within a nutrient gradient were studied in an oligotrophic pond with special reference to the diel fluctuations of cell volumes and frequency of dividing cells (FDC) at each season using an in situ gradostat. The predominant phytoplankters (Cryptomonas ovata in spring and autumn, Crucigenia rectangularis in summer and Chlamydomonas elongus in winter) exhibited moderately phased division during each season. These diel cycles could be regressed onto a sine curve to give a highly significant fit. The diel patterns in all gradostat chambers and periods were almost the same except for slight variations in the FDC. This shows that the diel pattern of cell division was governed mainly by the light:dark cycle during the 24 h, without regard to trophic differences of the aquatic environment. The mean growth rates of most phytoplankters were higher in the mesotrophic zone than in the eutrophic zone during each season. In winter, the growth rate of Chlamydomonas elongus was evidently greater during the seventh day of the experiment (Period III) than during the first day (Period I) in the mesotrophic chamber. As Chlamydomonas species occur as mesotrophic species in natural waters, Chlamydomonas elongus must acclimatize easily from the oligotrophic habitat to the mesotrophic environmental condition.

Spring bloom in a hypereutrophic lake, Lake Kasumigaura, Japan—V: Factors controlling natural population of phytoplankters

Abstract Temperature was the limiting factor controlling the multiplication rate and standing stock of natural population density of phytoplankters in the lake of Tsuchiura Harbor during the spring bloom of 1980. The temperature relationship of the multiplication rate could be expressed as an Arrhenius equation during the spring bloom. The species composition of the natural phytoplankton community, on the other hand, was affected chiefly by combination of the ambient nutrient concentrations of ammonium, nitrate, phosphate and silicate. Although many phytoplankton species occurred, one temperature relationship appeared to hold for mixed species of the natural community from 4.4 to 24.9° C.

Temperature dependence of filament length of Anabaena spiroides Klebahn var. crassa Lemm.

Temperature dependence of filament length ofAnabaena spiroides Klebahn var.crassa Lemm. was examined for a strain isolated from Lake Kasumigaura, Japan. The length of the algal filaments is shown to have good correspondence with the thermal master reaction of cell multiplication.