Figs 26-28 - uploaded by Gianfranco Novarino
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Achnanthes Iongipes: TEM views of girdle bands, showing the poroid occlusions. Scale bars = 1 pn.
Source publication
The girdle of Achnanthes longipes has been studied using scanning and transmission electron microscopy. An examination of 132 isolated bands showed that they can be classified into 3 main morphological types, all of which are usually open at one end, and bear poroids with occlusions recalling those of the valve poroids. The most advalvar band (band...
Contexts in source publication
Context 1
... of poroids scarcely visible from the outside. In internal views (Figs 14, 15,20-22), the poroids are usually circular, about 0.2-0.4 pm in diameter, and set about 0.6-0.9 pm apart. Variations in the number and morphology of the poroids are possible. A single band with 3 rows of poroids was found. Poroids from opposite rows may be partially fused (Fig. 28), and those ftom the most abvalvar row may be elongated, recalling the appearance of the poroids of the valvocopula (Fig. 20). The poroid occlusions are similar to those of the valvocopula (Figs ...
Context 2
... margin (arrows); PV = rapheless valve. Fig. 20. Internal view of band with an abvalvar row of elongated poroids. similar to those of the valvocopula (compare Figs 8-13). Fig. 21. Internal view of band with the usual 2 rows of circular poroids. Fig. 22. Internal view of band similar to Fig. 21. but with much longer crenations of the pars interior. Fig. 26. The valvocopula. Fig. 27. Type 2 band. Fig. 28. Type 2 band, with two partially fused poroids ...
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Citations
... They comprise one of the most abundant algal groups globally and are important in benthic and planktonic algal communities in freshwater, marine, and terrestrial habitats. A. brrevipes var intermedia belongs to the genus Achnanthes [19,20]. Her basionym is Achnanthes intermedia Kützing 1833, and her synonym is Achnanthes intermedia Kützing 1833; Achnanthes subsessilis Kützing 1833; Achnanthidium brevipes var. ...
... intermedia (Kützing) Cleve, coexist with the genus Bacillus represented by Brevibacillus agri and Paenibacillus sp., these thermophilic bacteria are of great interest due to their biotechnological importance as a source of thermostable enzymes and industrial products [21,22]. Figure 6: (20)(21)(22). SEMs of genus Bacillus represented by Brevibacillus agri and Paenibacillus sp. (23)(24). ...
The diversity of diatoms in the hot springs of the Comanjilla geothermal zone in northern Guanajuato, Mexico was studied. Hot springs are extreme ecosystems that, despite having high temperatures, constitute an environment for many thermophilic microorganisms (bacteria, cyanobacteria, and diatoms). The thermal water studied is classified as hyperthermal water (45°C to 100°C), of deep origin, and with low mineralization, are of type sulfuric sodium chloride, since the dissolved content of hydrogen sulfide (H2S) is found in concentrations higher than 1mg/L, and its smell is similar to the one of rotten eggs, presents a pH of 7.6 to 9.1 that represents neutrophilic to alkaliphilic environments, with a variable electrical conductivity (EC) (658-698 µs / cm) and total dissolved solids (TDS) (314-24 ppm). In the same way, these hot springs present microbial mats that consist of several stratified layers of green and orange color of 100 cm 2 , each one, which are dominated by specific types of microorganisms such as bacteria, cyanobacteria, but mainly diatoms, the latter were studied applying the scanning electron microscope and the optical microscope. The morphological characteristics observed in the optical microscope and in the scanning electron microscopy indicate the presence of diatoms of the Bacillariophyceae class, represented by Sellaphora disjuncta (55%), Achnanthes brevipes var. intermedia (45%). This diatom present in thermophilic microbial mats in the sulphurous geothermal zone of Comanjilla represents: a) the first report of said microorganisms in the study area and Mexico; b) an ecosystem of great interest from the biotechnological and industrial point of view; c) an important taxon in terms of diversity and technology; d) an applications in biofuels, environmental monitoring, wastewater treatment, manufacture of fertilizers, production of secondary metabolites, medical compounds, energy sources and food industry and within nanotechnology. It is important to mention that the physical and chemical characteristics of thermal water such as temperature, pH, dissolved solids, electrical conductivity, hardness, alkalinity and silica concentrations, were the major environmental factors influencing the distribution of diatoms in sulphurous hot springs.
... They comprise one of the most abundant algal groups globally and are important in benthic and planktonic algal communities in freshwater, marine, and terrestrial habitats. A. brrevipes var intermedia belongs to the genus Achnanthes [19,20]. Her basionym is Achnanthes intermedia Kützing 1833, and her synonym is Achnanthes intermedia Kützing 1833; Achnanthes subsessilis Kützing 1833; Achnanthidium brevipes var. ...
... intermedia (Kützing) Cleve, coexist with the genus Bacillus represented by Brevibacillus agri and Paenibacillus sp., these thermophilic bacteria are of great interest due to their biotechnological importance as a source of thermostable enzymes and industrial products [21,22]. Figure 6: (20)(21)(22). SEMs of genus Bacillus represented by Brevibacillus agri and Paenibacillus sp. (23)(24). ...
... Achnanthes sensu stricto differs from other monoraphid diatoms by the robust, large size of the species, growing on thick elongate stalks (Round et al. 1990;Novarino 1992;Lange-Bertalot & Compère 1997;Toyoda et al. 2003). The distinctly punctate striae have cribra in the areolae (Toyoda et al. 2003(Toyoda et al. , 2005aToyoda & Williams 2004) and many species have a rapheless sternum on the rapheless valve that is offset to one side relative to the raphe sternum (e.g. ...
... (Mann, 1982), etc.), or from the raphe, at the terminal nodule on the valve face (Hoagland et al.,1993, e.g. Achnanthes longiceps (Daniel et al.,1 987;Novarino, 1992) and A. minutissima Kütz (Roemer et al., 1984). Pads do not differ much from stalks: they are even called ‚short stalks'. ...
Epiphytic diatoms perform a variety of ecological functions. Diatoms are important primary producers and sources of oxygen which can modify the chemistry of the surrounding aquatic environment. They may live attached to plant surfaces with the help of extracellular polymeric substances and compete with plants for resources (e.g., light, nutrients). Thus, they represent an excellent model system for studies on interactions between epiphytes and their host plants under different environmental conditions. Further, the practical usage of epiphytic diatoms in biomonitoring begs questions concerning substrate specificity, diatom biodiversity, and species delimitations. This review focuses on specific aspects of freshwater epiphytic diatom ecology as adaptations for epiphytic way of life, epiphyte-host relationships, and implications for biomonitoring.
... It was observed that A. secretitaeniata has valvocopulae which are open-ended at both poles. Commonly, Achnanthes taxa form bands with some bands open at one side, which are combined and piled up by turns (e.g., Novarino 1992, Toyoda et al. 2003, Toyoda and Williams 2004, Toyoda et al. 2005a, 2005b, 2005c. These open-ended bands strengthen the structure of cell wall. ...
A new monoraphid diatom, Achnanthes secretitaeniata, is decribed from brackish water in the coast, Yamada-machi, Shimohei-gun, Iwate Pref., Japan. Cell shape is more or less linear with rounded extremities. Rapheless sternum grows close to the margin of the araphid valve. Araphid valve margin is well developed, but does not form marginal ridge as in A. yaquinensis and A. subconstricta. Valvocopulae and copulae are open- ended at both poles of valve. This species is closely related to A. brevipes C. Agardh var. intermedia (Kütz.) Cleve, but, they can be easily distinguished from each other by the position of rapheless sternum and the structure of valve margin on their araphid valves.
... The cribra in A. longipes, A. subconstricta, A. yaquinensis and A. javanica var. javanica Grunow are almost round, whereas A. crenulata has a more complex network of cribra (McIntire & Reimer 1974;Novarino 1992;Toyoda et al. 2003). Some other diatom species have similar cribra, such as species of Medlinia P. A. Sims, Florella portoricensis Navarro and some species of Isthmia C. Agardh (Navarro 1996;Sims 1998). ...
... The arrangement of the areolae on the copulae and their shape are both useful taxonomic characters for distinguishing between Ach-nanthes species. For example, A. longipes has two rows of differently shaped areolae, A. javanica has two rows of small areolae on its valvocopula and A. subconstricta has three or more rows on each girdle band (see Novarino 1992;Toyoda et al. 2003). ...
The present study clarifies the fine structure of the vegetative frustules, initial valves and perizonium of Achnanthes crenulata Grunow. The valves of the vegetative cell are distinctly linear-lanceolate with an undulate margin. The valve face is quite flat and in girdle view is smoothly curved as in species of Gephyria (Bacillariophyceae). However, the valve face of the initial cells is slightly rounded and does not have an undulate margin. Furthermore, the rapheless sternum is centrally positioned along the apical axis of the araphid initial valve. As this taxon develops from auxospore to initial valve, it forms only longitudinal perizonial bands; no transverse bands arise. The perizonium consists of three silicified bands: one large, central longitudinal plate and two bands that underlie this plate; these two bands are either open or closed. This taxon has several conspicuous structures compared to other marine species of Achnanthes, but the structure of the perizonium supports the position of A. crenulata within Achnanthes sensu stricto.
... The evidence supporting the position of A. brevipes as a member of the Mastogloiales includes the possession of two lobed or H-shaped plastids with a central pyrenoid, arranged fore and aft in the cell, as well as cribrate pores in both the valves and girdle bands. Achnanthes brevipes is a synonym of Achnanthes adnata Bory (Toyoda et al., 2005), the type of Achnanthes sensu stricto (see Round et al., 1990), which largely comprises robust, marine or brackish species (see also Novarino, 1992;Toyoda et al., 2003), in contrast to the smaller, predominantly freshwater achnanthoid diatoms. Other monoraphid genera have contrasting chloroplast types and arrangement (usually only one chloroplast per cell), a variety of pore types and, usually, non-porous girdle bands. ...
Despite variation in their protoplast organization and wall structure, monoraphid diatoms have traditionally been grouped as a single family or order, intermediate between the araphid and biraphid diatoms. However, the predominantly marine or brackish species of Achnanthes sensu stricto share protoplast and frustule features with representatives of the Mastogloiales rather than with other monoraphid diatoms. Meanwhile, studies of morphogenesis in Achnanthes have revealed that cells become monoraphid by filling in one raphe system during valve formation, indicating that the monoraphid condition is derived rather than primitive. Evidence from light and electron microscopy is presented to support the transfer of Achnanthes to the Mastogloiales, and an emended description of the order is given. It is concluded that the Achnanthales sensu Round et al. is a paraphyletic group and that the closest relatives of the various monoraphid genera must be sought among other raphid diatoms.
... Fine-structure of Achnanthes yaquinensis 275 more rows on each girdle band (Novarino, 1992;Toyoda et al., 2003). noted that several elements of the raphe system (e.g. ...
This study clarifies the fine structure of the vegetative and initial valves of Achnanthes yaquinensis and briefly compares them to other Achnanthes species. It also elucidates the structure of the perizonium, based on auxospore development in short-term cultures. The araphid valve has marginal ridges and terminal spines that allow connecting valves to form a chain. The terminal spines develop from the rapheless sternum. The complete cingulum consists of 3–5 split bands with two rows of areolae. These features can be used to discriminate species within the genus. Sexual reproduction is isogamous with two mother cells producing two auxospores, which are enclosed in mucilage. The perizonium develops on one side of an auxospore only, comprising one large central longitudinal band and four closed bands. There are no transverse perizonial bands. The raphid valve of the initial cell forms first, underneath the longitudinal perizonium, followed by the araphid valve, which is not covered by any perizonial bands. The araphid valve of the initial cells lacks a marginal spine, and the rapheless sternum lies more centrally than in the vegetative cell. The relationship of the genus Achnanthes to other monoraphid diatoms is discussed briefly.
... Many special structures providing primary differences between species in Achnanthes sensu lato have been referred to by many researchers since Bory established the genus. In particular, the structure of areolae on the valve, occluded by complex cribrae, and its presence on the girdle bands (Round et al. 1990, Novarino 1992, Toyoda et al. 2003. Many other species in Achnanthes sensu lato , particularly those now placed in Achnanthidium , have no volae or cribrae, but have poroid areolae occluded by hymenes, and non-porous bands (Bukhtiyarova & in the taxonomy of this genus (see Round et al. 1990, Toyoda et al. 2003. ...
... In spectra taken close to the end bearing the collar (a structure interposed between the stalk and the mucilage-producing pole of the raphid valve: see Daniel et al. 1987, fig. 9;Novarino 1992 and Novarino & Muftah 1992, fig. 15), the silicon peaks were much higher than those visible in spectra taken at the opposite end (Figs lc, d). ...
Energy-dispersive X-ray microanalysis shows that the mucilage stalk of the diatom Achnanthes longipes contains calcium, magnesium, silicon, and other elements usually present in small amounts. Calcium and magnesium are probably present in the form of carbonates (high magnesian calcite). There appears to be more silicon towards the stalk collar than towards the part of the stalk which adheres to the substrate. This suggests that the deposition of silicon within the stalk could be related to intracellular deposition. The stalk also contains much sulphur. This may be attributed to sulphated polysaccharides, whose presence has already been demonstrated by means of cytochemical investigations.
