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Some observations on the girdle of Achnanthes longipes
Abstract and Figures
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 1 or valvocopula) has a single row of elongated poroids on the pars exterior. The poroids have a groove-like appearance in internal views. The band interlocks with the valve following the complementary shape of its pars interior and the internal valve margin. Type 2 bands, which follow the valvocopula in the abvalvar direction, have a ligula or ligula-like expansion at the closed end, with no antiligula; their pars exterior usually bears 2 rows of circular poroids. A type 2 band seems to interlock with the valvocopula via its crenulate pars interior. The crenations may interact internally with the poroids of the valvocopula, or the cavities marking the limit between pars interior and pars exterior of the valvocopula. Presumably, type 2 bands also interlock with other type 2 bands. Type 3 bands follow type 2 bands in the abvalvar direction. They differ from type 2 bands especially in the smooth pars interior, which probably makes the interlock with type 2 bands looser than between type 2 and 1 bands, or between band 1 and the valve. Mature cingula have a total of 6 bands each. In addition to the single type 1 band, there are probably four type 2 bands and one type 3 band.
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... 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.
... 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. ...
... 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.
Achnanthes grunowii Toyoda & D. M. Williams was first described by Grunow in Cleve and Grunow (1880), as a variety of A. javanica Grunow, A. javanica var. rhombica. It is shown that the valve face of this taxon is rhombic in shape, and there are marginal and terminal ridges as well as terminal orbiculi on the ARV. The striae stand in more than three rows between costae on the valve, and the areolae stand in more than four rows on the copulae. In contrast, A. javanica var. javanica has the marginal ridge but no terminal spine, and terminal orbiculi and striae stand in two rows on the valve and small areolae stand in two rows on the valvocopula. These features support the view that A. javanica var. rhombica should be considered an independent species. However, the specific epithet rhombica was used by Østrup (1910) and Meister (1937) in this genus. Hence the new specific epithet grunowii is selected.
A new monoraphid marine species, Achnanthes pseudolongipes, is described. The structure of its valves and girdle resemble those of A. Zongipes Agardh, as well as the shape of the plastid. However, A. longipes has biseriate striae on both valves, whereas A. pseudolongipes has uniseriate striae on the raphid valve and biseriate (or triseriate) on the araphid valve. In the genus Achnanthes sensu stricto, only A. pseudolongipes possesses both uniseriate and biseriate striae. The number of striae between costae is one of the most effective features of the valve for the identification of taxa in the genus Achnanthes sensu stricto.
The morphology and fine structure of two marine mooraphid diatoms, Achnanthes javanica Grunow and A. subconstricta (Meister) comb. Nov. (= A javanica var. subconstricta Meister) have been investigated.Observations on the valves of type material (Grunow in Cleve & Möller 1878) of A. javanica show them to be lanceolate to linear in shape with a marginal ridge on the araphid valve but lacking terminal orbiculi. Conversely, A. subconsticta has a marginal ridge and special marginal spines as well as terminal orbiculi. From SEM observations in girdle view, A. subconstricta. These features support the view that A. subconstricta should be considered an independent species.
The morphology and fine structure of six species of the monoraphid diatom genus Cocconeis Ehr. have been investigated. The raphid valve is concave and thinner than the convex araphid valve. The vela are located near the internal openings of the areolae in the raphid valve but near the outer surface in the araphid valve. The fine structure of these plates varies very little among the species examined except for the araphid valve of Cocconeis pediculus. The raphe is a simple slit with parallel sides.
The raphe endings in the central area are somewhat dilated on the outer surface but undilated and bent slightly towards the valve margin on the interior.
Each complete cingulum consists of three plain imperforate girdle bands and includes a robust valvocopula. The valvocopulae of the raphid valve frequently bear fimbriae, the morphology of which is distinct for each species.
The central area of the valve is variable in the araphid valve of Cocconeis klamathensis. All taxa show a tendency towards irregularity in the rows of striae on one side of the central area in the raphid valve.