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New Blennothrix-species (Cyanophyceae/Cyanobacteria) from Nepal

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... Neighboring cells are connected through pores in their cross walls (microplasmodesms), the number and position of which are characteristic of the genera, and similar pores can sometimes be found on the outer cell walls, especially near the cross walls (Guglielmi and Cohen-Bazire, 1982a). Trichomes are capable of fragmentation (forming hormogonia) or complete disintegration into separate cells (Geitler, 1942(Geitler, , 1960Watanabe and Komárek, 1989). Fragmentation proceeds after the formation of fine mucilaginous lamella between neighboring cells or via so-called necridic (sacrificial) cells (or necrids). ...
... Blennothrix Kützing ex Anagnostidis et Komárek (Fig. 19) The thallus is mucilaginous, expanded or fasciculate and lengthened, cylindrical, filamentous or tufted, flaky, rarely hemispherical and cushion-like, up to 2 cm high, occasionally free floating, forming olive-green to black-green, bright to dull blue-green, blackish, rarely red-brown or black-violet masses. Filaments are straight or slightly undulating and entangled, in divaricated (spread apart like branches) or sparsely falsely branched fascicles or tufts, often with a special type of branching ("coleodesmoid," not "plectonematoid"; Watanabe and Komárek, 1989;compare Figs. 18B and 19). ...
... However, this character cannot be used without exceptions and it is usable with certain reservation in few cases only. to taxonomic delimitation of genera, and from which few were sometimes neglected, were, e.g., the trichome width, the ultrastructure of cells, the ratio of cell length to width, or several important biological markers, e.g., the type of fragmentation of the trichomes and hormogonia formation, existence of meristematic zones and type of necridic cells (Watanabe and Komárek 1989;Ballot et al. 2004;Malone et al. 2015). ...
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The criteria for cyanobacterial taxonomy have changed substantially in the last several years. The most important of the newly introduced methods are molecular sequencing and the genetic approach, which is considered as a major criterion for the classification of organisms. However, molecular results have not always been in agreement with those of the traditional classification system based on morphological or ecological criteria. Thus, application of the polyphasic approach provides the best means of conducting taxonomic practice, and the coincidences and correlations of various criteria must be discovered. Here are discussed the main problems associated with the taxonomy of simple, relatively wide filamentous cyanobacteria with short vegetative cells, but without prominent cells (heterocytes, akinetes). Examples were selected from the family Oscillatoriaceae, which was traditionally based only on morphological criteria. The main markers for delimitation of this family after revisions and the relations and consequences of various genera are discussed, as well as a proposal to base the final revision of this family according to modern criteria. The members of this cyanobacterial group are distributed in numerous ecosystems around the world and form also distinct communities in tropical America.
... We have analysed freshwater populations of Blennothrix ganeshii Watanabe & Komárek, collected in 2004 in two rivers in Mexico and found them to conform closely to the original description (Watanabe & Komárek, 1989). The TEM demonstrated that the Blennothrix we studied did indeed exhibit multiple initiations of cross-wall closures (Figs 17, 18, numbered 1-3), as did the TEM images in the original description of this organism (loco citato, p. 76, fig. ...
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Populations of the benthic diazotrophic cyanobacterium Hydrocoleum Kützing (1843) are widely distributed in coral reefs and lagoons of tropical oceans, where they contribute to benthic nitrogen fixation. We compared the morphological, molecular and physiological features of 31 freshwater and marine Hydrocoleum populations from geographically different localities and five specimens from herbaria. Our aims were to compare the features of Hydrocoleum with the morphologically and phylogenetically related genera Trichodesmium Ehrenberg ex Gomont 1892 and Blennothrix Kützing 1843, and to provide the basis for the validity of the genus Hydrocoleum. The Hydrocoleum populations were distributed over a wide range of sizes, showing no consistent inter-population grouping and leaving no gaps between groups that were traditionally attributed to different species. Transmission electron microscopy showed regular cell division rhythms in all Hydrocoleum populations with each cell division completed before the next one was initiated, similar to that described for Trichodesmium. In contrast, Blennothrix populations exhibited multiple initiation of cross-wall formation. Most Hydrocoleum populations fixed nitrogen at consistently higher nightly rates. The phylogenetic analysis of 16S rRNA and nifH gene sequences placed all morphologically distinct Hydrocoleum and Trichodesmium populations within a tight cluster. Neither of the analysed genes brought any further resolution of phenotypically and ecologically distinguished forms. However, freshwater morphospecies of Blennothrix together with the type species Blennothrix vermicularis Kützing were separated from the Trichodesmium/Hydrocoleum cluster, which further supported the genotypic distinction between the compared taxa, in addition to the fact that they also differ in morphology and ecology. We concluded that the genus Hydrocoleum possesses unique features that warrant its maintenance in the botanical classification system and that its introduction in bacteriological manuals as a valid cyanobacterial genus is acceptable.
... This perennial cyanobacterium grows in large mats and is an important biotic component in its microhabitat . Studies of B. ganeshii have concerned taxonomic and ecological information (Anagnostidis & Komárek, 1988;Valadez-Cruz et al., 1996;Komárek, 1998;Watanabe & Komárek, 1989;Montejano et al., 2000;Cantoral & Aboal, 2001;Beltrán-Magos et al., 2005;Carmona et al., 2005) but studies of calcification processes are sparse. The purpose of this study is to evaluate the mechanisms as well as environmental and biological factors involved in B. ganeshii calcification in four tropical streams in central Mexico. ...
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Geochemical, mineralogical and microbiological data from four freshwater streams in central region of Mexico indicate the importance of Blennothrix ganeshii mats (Cyanobacteria, Oscillatoriales) in promoting the formation of calcium carbonate crystals. The streams were characterized by alkaline waters and relative physicochemical stability during three seasons (cold dry, warm dry and warm rainy). Calcification took the form of a thick, dense layer of calcium carbonate crystals surrounding the extracellular polymeric substances produced by B. ganeshii filaments, giving an appearance of micritic tubes (structures formed by crystallization in the spaces between filaments) along the sheath surfaces. The precipitate was analyzed using X-ray diffraction and energy dispersal X-ray spectrometry, and the calcite crystal habit was determined. The photosynthetic activity of cyanobacterial growth and the presence of abundant extracellular polymeric substances and epiphytic species promote the absorption of ions and mineral nucleation on the surface of the sediment and contribute to the formation of travertine in tropical regions.
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Morphology of the nucleoid in the halobiotic, planktic cyanophyte Cyanothece halobia Roussomoustakaki et Anagnostidis was investigated. DAPI fluorescence staining revealed that nucleoid morphology strongly resembles that of Cyanothece aeruginosa (Nageli) Komarek. The nucleoids consist of many globular, oval, and elongated skeins of DNA connected by thin filaments of DNA. Red fluorescence of chlorophyll is dispersed among the patches of DNA. In some cases DNA is concentrated into one large skein located in the cell centre. A large skein of DNA was also recorded in dividing cells at the place of cell partition. It was confirmed that nucleoid morphology is a reliable character distinguishing Cyanothece from other Synechococcus-like organisms. A similar nucleoid morphology was observed in other cyanophytes (coccal or filamentous) possessing keritomized cells (cells with irregularly arranged dark and light spaces observable in a light microscope, caused by grouped thylakoids), e.g. Stanieria and Tychonema. I propose that nucleoid morphology (number, size and compactness of the DNA skeins) correlates with the extent of keritomy. The relationship of nucleoid morphology and thylakoid arrangement in algae possessing keritomized thylakoids is discussed.
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Geochemical, mineralogical and microbiological data from four freshwater streams in central region of Mexico indicate the importance of Blennothrix ganeshii mats (Cyanobacteria, Oscillatoriales) in promoting the formation of calcium carbonate crystals. The streams were characterized by alkaline waters and relative physicochemical stability during three seasons (cold dry, warm dry and warm rainy). Calcification took the form of a thick, dense layer of calcium carbonate crystals surrounding the extracellular polymeric substances produced by B. ganeshii filaments, giving an appearance of micritic tubes (structures formed by crystallization in the spaces between filaments) along the sheath surfaces. The precipitate was analyzed using X-ray diffraction and energy dispersal X-ray spectrometry, and the calcite crystal habit was determined. The photosynthetic activity of cyanobacterial growth and the presence of abundant extracellular polymeric substances and epiphytic species promote the absorption of ions and mineral nucleation on the surface of the sediment and contribute to the formation of travertine in tropical regions.
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Full-text available
The genus Blennothrix belongs to the family Oscillatoriaceae (subfamily Oscillatorioideae), differing from others in the subfamily by the presence of several trichomes in a sheath. Freshwater members of Blennothrix have been recently divided into eight species (Komárek 1998), with the taxon B. ganeshii Watanabe et Komárek reported from three sites in two tropical basins of the central region of Mexico. However, information on anatomical (vegetative and reproductive) characters and environmental distribution is scarce and species determination is uncertain. This study analyses the anatomical structure of Blennothrix populations distributed in different sites along the central tropical region of Mexico in order to determine the taxonomic status of the studied populations. Eight populations were sampled, with concurrent environmental data recorded. Morphological characters previously considered to be of taxonomic importance, as well as complementary features such as algal mat length, filament diameter, trichome width, length of cells, and thickness and shape of the sheath were measured in several filaments of each sample. Our results showed that all the observed populations in the central region of Mexico fit within the circumscription of B. ganeshii (Watanabe & Komárek 1989, Komárek 1998). However, two important morphological features were observed in all populations. First, branches were rarely present and varying in frequency from 1 to 3 trichomes per filament. Second, the presence of a transverse lamellation due to constriction in the longitudinal axis of the sheath was observed. Some morphological characters described for this species were extended.
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