Diatom
Online ISSN : 2186-8565
Print ISSN : 0911-9310
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Volume 21
Showing 1-13 articles out of 13 articles from the selected issue
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  • Seiichi Komura
    Volume 21 (2005) Pages 1-46
    Released: December 11, 2012
    JOURNALS FREE ACCESS
    Eight new genera, nine new species and one new combination are described from early Miocene marine sediments which outcrop along Nobi beach, of the Miura Peninsula, that faces Tokyo Bay: Trisystema multicirculare gen. et sp. nov., Collumicylindrus annuliformis gen. et sp. nov., Omphalophortron giganteum gen. et sp. nov., Omphalophortron blysmum (Barron) comb. nov., Fusiformella tubifera gen. et sp. nov., Fovirhombus rugosus gen. et sp. nov., Plegmolobos polymorphus gen. et sp. nov., Heterangion acanthophorum sp. nov., Annularius foveatus gen. et sp. nov., and Callimastogloia eucalla gen. et sp. nov.1) Trisystema has a Distephanosira-like frustule with a trinary system valve linkage.2) Collumicylindrus is similar to Craspedodiscus but distinguishable from the latter genus because of the former having a large pericentral collar.3) Omphalophortron has a pit-like deep depression at the centre of the watchglass-shaped valve and each loculate areola is occluded by a composite cribrate velum.4) Fusiformella resembles Rossiella in many aspects but differs from the latter by having loculate areolae through the lanceolate valve, occluded by the cupola-shaped cribra attached to the internal foramen at the edge and an elongate tube extending from the internal subapical rimoportula to the exterior.5) Fovirhombus rugosus is an actinocyclid with pit-shaped depressions scattered over the wide imperforate field at the centre of the rhombic valve.6) Plegmolobos polymorphus is proposed as having a trilobed pillbox-shaped frustule distorted about the pervalvar axis.7) Heterangion acanthophorum is recorded as the second species in this biddulphioid genus and distinguished by opposed protrusions from the hyaline valvar margin beneath unequal-sized elevations each with a topmost ocellus.8) Annularius differs from Navicula sensu stricto in having broad crescent-shaped pitted fields between the thick-silicified apical raphe-sternum (with an arcuate, not plicate, raphe) and the circumferential semicylindrical loop.9) Callimastogloia is closely related to Mastogloia but differentiated from it in having a pair of completely closed partectal rings.
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  • Hiroyuki Tanaka, Tamotsu Nagumo
    Volume 21 (2005) Pages 47-55
    Released: December 11, 2012
    JOURNALS FREE ACCESS
    Puncticulata ozensis sp. nov. is described from Lake Oze (Oze-numa) located between Gunma and Fukushima Prefectures, central Japan. The valve iface of this species ig 'characterized by a central area composed of approximately radial rows of areolae andi valve face fultoportulae arranged in a circular pattern. The valve marginal area has striae with two or three openings of rimoportulae located at the proximal end of slightly short striae. All interstriae continue to the valve edge. Mantle fultoportulae relatively close to each other on every 2, or in rare cases 3, interstriae, and the absence of branching interstriae on the mantle are also useful defining characteristics. The new species is compared to similar species of the genus Puncticulata Håk.: P bodanica (Grunow) Håk. var. affinis (Grunow) H. Tanaka & Nagumo, P. comta (Ehrenb. ) Håk., P. praetermissa (J. WG. Lund)Håk. and P. radiosa (Lemmerm. ) Håk.
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  • Akihiro Tujil, David M. Williams
    Volume 21 (2005) Pages 57-60
    Released: December 11, 2012
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    Morphological variation of Himantidium pectinale (=Eunotia pectinalis) and Fragilaria pectinalis var. undulata (=Eunotia pectinalis var. undulata) were examined using type slides in BM. The lectotype of Fragilaria pectinalis var. undulata is designated using a slide BM67796 from Ralfs' collection in BM. Eunotia pectinalis var. undulata should be a synonym of Eunotia pectinalis var. pectinalis.
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  • Shigeki Mayama
    Volume 21 (2005) Pages 61-70
    Released: December 11, 2012
    JOURNALS FREE ACCESS
    The general public is generally not very familiar with diatoms, although they play very important roles in the global ecosystem and are in a number of ways closely related to our existence. One approach that promises to be helpful in terms of increasing the popular awareness of diatoms is the exhibition of diatoms. One such exhibition was produced in the context of a collaboration between the biology and art departments of Tokyo Gakugei University. The exhibition featured the following items: artworks representing the morphological beauty of diatoms as a motif, graphic displays showing various biological and applied aspects of diatoms, stereograms of diatoms, and diatom slides and specimens accompanied by light and scanning electron microscopy. A questionnaire survey to participating visitors of the exhibition suggested that the morphological beauty of the diatoms was sufficient to leave a strong impression, and the graphic designs and the spatial arrangement of the exhibition facilitated the acquisition of information regarding various features of diatoms; moreover, the observation of diatoms via the visitors' operation of light and electron microscopes enhanced their overall interest in diatoms. In addition, answers onthe questionnaire indicated that word-of-mouth advertisement was the most effective means of disseminating information about the exhibition to members of the public who had not yet known about diatoms.
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  • Yuko Fujita, Taisuke Ohtsuka
    Volume 21 (2005) Pages 71-89
    Released: December 11, 2012
    JOURNALS FREE ACCESS
    The diatom flora from paddy fields in northern Laos was studied. Soil samples were collected from a depth of 0-1 cm in 6 paddy fields in the Nam Ben River basin in October,2003, and 8 paddies in Ay village in September,2004. In total,104 diatom taxa belonging to 28 genera were identified. They are illustrated together with 11 unidentified diatom taxa. The dominant genera were Nitzschia and Pinnularia. Navicula pygmaeformis H. Kobayasi is transferred to a taxonomically more suitable genus, as Fallacia pygmaeformis (H. Kobayasi) Y. Fujita et Ohtsuka comb. nov.
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  • Takashi Terasaka, Tamotsu Nagumo, Jiro Tanaka
    Volume 21 (2005) Pages 91-105
    Released: December 11, 2012
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    We observed the morphology of the marine pennate diatom genus Licmophora in Japan using light and scanning electron microscopy, and identified the following four common species: L. californica Grunow, L. communis (Heib. ) Grunow, L. flabellata (Grey. )C. Agardh, and L. paradoxa (Lyngb. ) C. Agardh. They were distinguished from each other by 1) colony structure,2) chloroplast shape,3) shape of valves and frustules,4) winding degree of central rib of valvocopula,5) depth of septum,6) areola shape,7) velum structure,8) number and arrangement of rimoportulae,9) fine structure of head rimoportula,10) number of apical slits and 11) presence of spines. Especially colony structure, areola shape, velum structure and fine structure of the head rimoportula were the most definitive characteristics among the species studied. The fine structure of the head rimoportula is a new distinguishing character revealed in the present study.
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  • Akio Nigorikawa, Yasuo Hasegawa
    Volume 21 (2005) Pages 107-118
    Released: December 11, 2012
    JOURNALS FREE ACCESS
    Lake Obuchi-numa is located in Aomori Prefecture, northeast Japan and is known as a brackish-water lake, connected to the Pacific Ocean by a narrow water channel. The water qualities, i. e. pH, conductivity, turbidity, DO, temperature and salinity, were measured in 1997. At the same time surface layer oozes and epiphytic samples from aquatic plants or stakes were collected to analyze the diatom assemblages. In this paper the diatom assemblages from these samples and the hydrological conditions are reported. The results are as follows 1) Most areas are contain polyhaline water, although mesohaline water partially exists in the innermost part of the lake. It is thought that the present water condition is caused by the extension of the water channel and dredging of the lake bottom.2) The 99 taxa belonging to 42 genera and 32 taxa to 17 genera were found from the oozes and the epiphytic samples respectively.3) The dominant species in the oozes were Melosira moniliformis and Cocconeis scutellum. On the other hand, the epiphytic samples were characterized by Melosira moniliformis and M. nummuloides.
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  • Hiroyuki Tanaka, Tamotsu Nagumo, Kaoru Kashima
    Volume 21 (2005) Pages 119-130
    Released: December 11, 2012
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    Fossil diatom assemblages were documented from outcrops of the Tsumori Formation (Middle Pleistocene) distributed along the Kanayama River, Mashiki Town, Kumamoto Prefecture, Kyushu, Japan.102 taxa in 40 genera were identified for fossil freshwater diatoms in three siltstone samples (KUM-102,104,108) from the Formation. The diatom assemblage of three samples showed dominant taxa of araphid pennate diatoms (14 taxa)with a fruquency of 43%, accompanied with centric diatoms (5 taxa) 27%, biraphid pennate diatoms (73 taxa) 18% and monoraphid pennate diatoms (10 taxa) 12%. Taxonomic information is described on seven species: Cyclostephanos kyushuensis H. Tanaka, Cocconeis placentula Ehrenb., Epithemia hyndmanii W. Sm., Gomphonema vibrio Ehrenb. var. subcapitaturn (Mayer) J. H. Lee, Navicula subcostulata Hust. var. rostrata Hust., Rhopalodia novaezelandiae Hust. and Stauroneis phoenicenteron (Nitzsch) Ehrenb. var. hattorii Tsumura. In the sample KUM-108, fossils of Epithemia hyndmanii were found attached to chips of wood.
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  • Kensuke Toyoda, David M. Williams
    Volume 21 (2005) Pages 131-133
    Released: December 11, 2012
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    Freshwater species Monogramma smithiana, which was described by Greville in 1866, is changed its classification to Achnanthes smithiana (Grey. ) Toyoda et D. M. Williams. The lectotype slide is designated (BM3353 in BM) from three syntype slides with light microscope observation.
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  • Shigehiko Arita, Taisuke Ohtsuka
    Volume 21 (2005) Pages 135-141
    Released: December 11, 2012
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    Valve outlines of 30 species of pennate diatoms from Lake Biwa were described by the arc-constitutive model advocated by Arita & Ohtsuka (2004). The model designs the valve outline as a combination of arc (including line) segments that are connected each other by a common tangential. The model described well all of the valve outlines examined, suggesting the versatility of the model for describing a variety of pennate diatoms. When symmetry was assumed, the model could express the valve outline with an adequately small number of free parameters. The number of free parameters necessary for describing outlines was 5-7 for biaxially symmetric valves,7-13 for single-axially symmetric valves, but 9-39 for “broken-symmetric” valves.
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  • Volume 21 (2005) Pages 143-146
    Released: December 11, 2012
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  • Volume 21 (2005) Pages 147-154
    Released: December 11, 2012
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  • Volume 21 (2005) Pages 155-162
    Released: December 11, 2012
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