Genus Cymbella Research Articles

Cymbella stomachsis sp. nov. (Bacillariophyta; Cymbellaceae), a new species from Guangdong Province, China

A new diatom species from the genus Cymbella C. Agardh is described from samples collected during a survey of freshwater diatoms from Modaomen Channel, Guangdong Province, China. With the aid of light microscopy (LM) and scanning electron microscopy (SEM), we give a detailed morphological description of Cymbella stomachsis sp. nov., which is placed in the genus Cymbella according to the shared features of asymmetry about the apical axis, deflection of the external terminal raphe fissures towards the dorsal margin, and the presence of apical pore fields and stigmata. Although it shares some similar structural features with C. tumida, C. stuxbergii, C. stuxbergioides, C. pesudostuxbergii, C. mexicana and C. australica, C. stomachsis sp. nov. is easily distinguished by the valve outline, the shape and density of areola, and the appearance of a lack of an intermissio at the central nodule. Especially, the structure of the intermissio is absent in similar taxa. This work is important for its enrichment of our understanding of the genus Cymbella and improvement of the database of diatom biodiversity and distribution in China.

The Perizonium Ultrastructure, Divided Apical Pore Fields, Various Pore Occlusions and Visible Intermissio of Cymbella (Bacillariophyceae) with Descriptions of Four New Species.

The initial valves of two Cymbella species are observed under a scanning electron microscope, and the perizonium ultrastructure of Cymbella is revealed for the first time. The perizonium is composed of alternate nodes and internodes and lacks transverse perizonium bands. Four new species, Cymbella apiculatophora sp. nov., C. hunanensis sp. nov., C. juglandis sp. nov. and C. menyuanensis sp. nov., are described using light and scanning electron microscopy based on epilithon samples collected from rivers in Hunan and Qinghai Provinces, China. Cymbella menyuanensis is a typical Cymbella species that closely resembles species in the group around C. cymbiformis Agardh, the type species of the genus. Cymbella apiculatophora is similar to C. sinensis Metzeltin & Krammer, while Cymbella hunanensis is closer to the C. hustedtii Krasske group. The last species, C. juglandis, has a cymbelloid valve outline, an obscured intermissio, internal occlusions of the areolae, dorsally deflected distal raphe fissures and a divided apical pore field at each apex, and it does not appear to belong to any group. In addition, new observations on C. cf. excisiformis Krammer and C. hustedtii are reported. The current concept of the genus Cymbella does not represent a monophyletic group as shown by molecular phylogenetic analyses. However, these analyses are still at the preliminary stage and are not yet sufficient to support a complete revision of the genus. Thus, although extremely diverse ultrastructural features are observed in the six Cymbella species investigated in this paper, we prefer to keep them within Cymbella at this moment for the sake of nomenclatural stability.

Cymbella liangyanlingii sp. nov. (Bacillariophyta, Cymbellaceae), a new diatom species from the upper tributary of Liujiang River, Guangxi Zhuang Autonomous Region, China

Cymbella liangyanlingii sp. nov. was collected from epilithic samples in the Liujiang River, Guangxi Zhuang Autonomous Region, China. Light microscopy (LM) and scanning electron microscopy (SEM) were used to describe the morphology of the new species, and in addition we provided detailed ecological information about this species. C. liangyanlingii sp. nov. has the features that assign it to the genus Cymbella, including the terminal raphe fissures deflected toward dorsal margin, apical pore fields present at each end on the valve and, for most taxa in the genus, one or more stigmata on the ventral side of the central area. The key diagnostic features that easily distinguish the new species from other similar species: 1) the inconspicuous central area, 2) three slit-like stigmata on the ventral margin, 3) the striae have no interruption on the valve margin, and 4) striae that are mostly uniseriate in the middle and biseriate (5–7) in the ends. This combination of features distinguishes C. liangyanlingii sp. nov. from congers such as C. liyangensis, C. distalebiseriata, C. alexandrovichii and C. hubeiensis. These findings can help us further understand the morphological and ecological information of the genus Cymbella in China.

Cymbella alexandrovichii sp. nov. (Cymbellaceae, Bacillariophyceae), a new cymbelloid diatom species with predominantly biseriate striae from South-East Asia

A new species from the genus Cymbella is described based on the morphological study using light and scanning electron microscopy. In the new species, striae are predominantly biseriate except for the central part of the valve, where they become uniseriate. Cymbella alexandrovichii sp. nov. is compared to 8 similar species of Cymbella that possess biseriate striae throughout the valve or only near the apices. Another species with biseriate striae—Gomphocymbellopsis guijiangensis­—was included in the comparison based on the similar morphology. In addition, 3 species of Cymbella are compared to Cymbella alexandrovichii sp. nov. herein, despite lacking biseriate striation. The new species can be distinguished from similar taxa by a combination of features: asymmetric lanceolate outline with convex dorsal margin, not protracted cuneate to bluntly rounded valve ends, predominantly biseriate striae and 2–3 ventral stigmata.

Three new cymbelloid species in the genera Cymbella, Cymbopleura and Delicatophycus from the mineral spring Crvena Voda near Skopje, Republic of North Macedonia

Mineral springs are unique habitats frequently inhabited by specific diatom species with restricted distributions. In the mineral spring Crvena Voda near Skopje, three cymbelloid taxa were observed, whose morphological characteristics differ from already known taxa. They are described here as: Cymbella parahelvetica sp. nov., Cymbopleura angustilanceolata sp. nov. and Delicatophycus fontinalis sp. nov. Cymbella parahelvetica sp. nov. is characterized by the absence of an apical pore field at the valve ends and by very densely arranged striae. Cymbopleura angustilanceolata sp. nov. can be distinguished from other Cymbopleura species by the valve outline, the shape of the central area and the stria density. Delicatophycus fontinalis sp. nov. can be differentiated from similar species by its strongly arched dorsal margin, its valve width and stria density.

Molecular and Morphological Investigations of Two Giant Diatom Cymbella Species from the Transbaikal Area (Russia, Siberia) with Comments on Their Distributions.

For the first time, a giant diatom species of the genus Cymbella from Lake Baikal was studied using molecular methods. Molecular and morphological investigations allowed to us to described one new species, Cymbella baicalaspera Glushchenko, Kulikovskiy and Kociolek sp. nov. This species is both morphologically similar and phylogenetically close to a second giant Cymbella species that we investigated here, identified by us as Cymbella himalaspera Jüttner and Van de Vijver in Jüttner et al. 2010. This species was first described from Nepal on the basis of a morphological investigation. Small morphological differences exist between the type population and specimens from Lake Baikal, but otherwise the two are identical. These very interesting results show that some Baikalian diatoms can be distributed more widely and are not only endemic to this ancient lake. Similarity between Cymbella baicalaspera sp. nov. and Cymbella himalaspera on the basis of both morphological features and their close phylogenetic relationships suggested by molecular data indicate they are sister species and an example of sympatric speciation. These results also suggest an early development of a species flock. This species group warrants additional research in terms of. their diversification and biogeography.

Cymbella biseriata sp. nov.—a unique living species of Cymbella Agardh (Bacillariophyceae) with biseriate striae

Alpine ponds are known biodiversity hot-spots and refugia for many rare and endangered species. They are also considered to be vulnerable habitats in terms of acidification, eutrophication, modification and climatic changes. Recently, a detailed study of diatoms in these habitats in North Macedonia has been started to evaluate their status and threats. During these studies, specimens of a species of Cymbella that lacked apical pore fields and had a small valve size were recorded. Scanning electron microscope observations revealed biseriate striae composed of small, slit-like to tilde-like areolae, a character so far not observed in any living representatives of the genus Cymbella. Herein, these specimens are assigned to the new species Cymbella biseriata sp. nov. based on detailed observations with light and scanning electron microscope. Comparison with similar taxa from the C. helvetica species complex and fossil species with biseriate striae is provided.

Vladinikolaevia, gen. nov. - a new enigmatic freshwater diatom genus (Cymbellaceae; Bacillariophyceae) from Mongolia

We studied a new freshwater cymbelloid diatom taxon collected from Mongolia with light and scanning electron microscopy. The monotypic genus Vladinikolaevia gen. nov., based on V. mongolica sp. nov, is described. The new genus is characterized by a combination of morphological features found in two well-known genera such as Cymbella and Encyonema. The raphe system is morphologically-similar to Encyonema but the presence of apical pore fields is similar to the genus Cymbella as presently circumscribed. There are other very interesting peculiarities found in V. mongolica sp. nov. that show it to be a distinct taxon. We discuss the morphology of this new genus in the context of valve morphogenesis and presence of primary and secondary valves. The description of this new genus from Mongolia supports our contention that Asia is home to many endemics, interesting and not yet described cymbelloid taxa.

Cymbelloid diatoms from the River Adegoy, Krasnodar Territory, Russia, with a description of a new species Delicatophycus porosus sp. nov. (Cymbellaceae, Bacillariophyta)

This is a taxonomic study of cymbelloid diatoms from the River Adegoy (Krasnodar Territory, Russia). During the survey 24 taxa were recorded including a new species of Delicatophycus. The morphology of Delicatophycus porosus sp. nov. was examined using light and scanning electron microscopy and compared to nine similar species. The new species can be distinguished from similar taxa by a combination of characters: dorsiventral valves with radiate to parallel striae, broadly rounded apices and apical pore fields. Other species found belong to the genera Cymbella, Cymbopleura, Encyonema, Encyonopsis and Reimeria.

Three new species of Delicatophycus M.J. Wynne (Bacillariophyta) from China, all possessing apical pore fields

Delicatophycus wulingensis sp. nov., D. qinghainensis sp. nov., and D. menyuanensis sp. nov., are described, illustrated, and compared to similar taxa. Two types of apical pore fields (APFs) in the genus Cymbella are defined. The three new Delicatophycus all possess the type II APF found in some species of Cymbella, i.e. the APF is divided by the distal raphe fissure into two areas, one larger than the other. They also share a further three distinct features: variable central dorsal portion of valve, stigmata, and a notch on the dorsal side of the distal raphe fissure. Since there are many species of Delicatophycus without APFs, such as D. sinensis M.J. Wynne, D. williamsii M.J. Wynne and D. chongqingensis M.J. Wynne; D. williamsii and D. liuweii Li both possess stigmata, thus proposed diagnostic characters for Delicatophycus are the tilde-shaped areolae and the dorsally curved distal fissures.

One new species of Cymbella C.A. Agardh (Bacillariophyta) from high altitude lakes in the Hengduan Mountains of Southwest China

This paper describes a new species of the genus Cymbella C.A. Agardh from an alpine lake in the Hengduan Mountains of southwestern China. A detailed morphological description of the new species, named Cymbella luoyulanae sp. nov., is presented; the description is based on light and scanning electron microscopy. The main features of C. luoyulanae are strongly dorsiventral valves with strongly reverse-lateral raphe branches near the proximal ends, a large central area occupying approximately a half of the width with the valve and slit-like areolae comprising striae that may be unseriate or partially biseriate. The new species has morphological characteristics that resemble those of C. heihainensis Y.Li et Gong, C. modicepunctata Krammer and C. asiatica Metzeltin, Lange-Bertalot et Y.Li, but it differs from these three species in details of size, valve shape, striae density, central area, and number of stigmata.

Morphological Variability of Some Species of the Genus Cymbella (Bacillariophyta) from Reservoirs of the Dnieper Cascade (Ukraine)

Morphological Variability of Some Species of the Genus Cymbella (Bacillariophyta) from Reservoirs of the Dnieper Cascade (Ukraine)

A new species of Cymbella (Bacillariophyceae, Cymbellaceae) from the Pavana River, Western Ghats, India

New diatom species from the genus Cymbella is described, Cymbella pavanaensis from the Pavana River situated in Pimpri-Chinchwad, Pune, Maharashtra, India. The new species description is based on detailed LM and SEM morphological observations. Comparison of the new species with similar, previously-described taxa is made. C. pavanaensis belongs to a group of small-celled species of the genus, which lack differentiated, rounded porelli comprising the apical pore fields. This taxon is reported from a moderately to the highly-polluted urban lotic system, which signifies that even the diatom flora of easily accessible habitats of India is yet to be fully documented.

Benthic diatom community response to metal contamination from an abandoned Cu mine: Case study of the Gromolo Torrent (Italy)

Environmental contamination has become a global problem of increasing intensity due to the exponential growth of industrialization. One main debated issue is the metal contamination of rivers receiving Acid Mine Drainage (AMD) from active/abandoned mines. In order to assess the quality of lotic systems, diatoms are commonly used, as their assemblage modifies on the basis of changes in environmental parameters. Benthic diatom changes were analyzed along the metal-impacted Gromolo Torrent (Liguria, NW Italy) with the aim of understanding the effects of input from the abandoned Libiola Cu mine. The results support the hypothesis that metals from AMD lead to massive changes in diatoms, resulting in low biological diversity and in a shift of dominance, passing from the genera Cymbella and Cocconeis to more tolerant and opportunistic species, such as Achnanthidium minutissimum and Fragilaria rumpens. The high concentrations of labile metals, measured through Diffusion Gradients in Thin-films (DGT) immediately downstream of the two AMD inputs in the torrent, corresponded to a sudden decrease in the presence of diatoms, indicating the possible reaching of acute toxic levels. In particular, A. minutissimum dominated the mining area and was positively correlated with Cu and Zn; whereas F. rumpens bloomed downstream of this area, where the metal content was diluted, and was positively correlated with As and Pb. Finally, an important abundance of Nitzschia palea and teratological forms of A. minutissimum and F. rumpens were observed downstream from the mine, indicating that metals may have an important impact on diatoms up to the torrent mouth.

Diatoms of the Cymbella sensu lato species of the two different eco-regions of the Indian Mountain Rivers

This paper describes Cymbella sensu lato (Cymbopleura, Delicata, Encyonema, Encyonopsis and Reimeria) species from two different ecoregions of India. In the present study, twenty-six diatom taxa belonging to the genus Cymbella sensu lato were identified. In the flora nineteen species were recorded from the Vindhya region while eleven from the Himalaya. All of them were first records for the Vindhyan rivers. Seven taxa were new records for the Himalayan river.

DiaCurv: a value-based curvature analysis application in diatom taxonomy

DiaCurv is a software application that uses a simple approach to calculating curvature by identifying the chord (length) and the sagitta (length) from a mid-point of an object or part of an object. This software application and associated R scripts provide the users with the possibilities to identify and apply curvature analysis in diatom taxonomy. Different taxa from the genera Cymbella and Luticola, with good size diminution series, were selected to validate curvature metrics for shape evaluations in taxonomy. The dorsal ventral curvature of Cymbella makes species within this genus a natural choice for comparison. In contrast, the lanceolate, elliptic-lanceolate to rhombic forms of species within Luticola are more problematic. Machine-learning techniques (principal component analysis and linear discriminant analysis (LDA)) were used to evaluate the curvature metrics for distinguishing diatom taxa. Selected taxa (C. aspera, C. cymbiformis, C. diversa, C. excisa, C. japonica, C. neogena, C. neuquina, C. parva, C. saxoicola, C. tumidula) were identified by valve curvature, except when valve shape was not a distinguishing character for the species. With the lanceolate, elliptic-lanceolate shapes of Luticola, curvature was effective in separating the linear-lanceolate forms (e.g., L. australomutica, L. goeppertiana, L. murrayi, L. saprophila), and some broadly lanceolate forms (L. crozetensis, L. subcrozetensis) but not elliptic-lanceolate forms within the same size range (e.g., L. katkae, L. pseudocharcotii, L. yellowstonensis). The experimental results indicated that LDA was more suitable for distinguishing taxa. Valve shapes which are circular, or centrally constricted or with polar differentiation or 3D in complexity may not be appropriate for curvature analysis unless specific parts of the valve are selected. The merits of this approach, or any other type of shape analysis, are that the subjective interpretation of shape differences between taxa is removed or reduced.

Cymbella marvanii sp. nov., a new Cymbella species from the French Pyrenees

A recent survey of the benthic diatoms in Pyrenean lakes led to the discovery of a species of Cymbella new to science. With light microscopy, Cymbella marvanii looks like a Cymbopleura species. With scanning electron microscopy, the observations show the presence of stigmata, a distinctive feature of the genus Cymbella. The proposed new species is compared with similar taxa belonging to Cymbella, Cymbopleura and Encyonema. In particular, the new species is compared with Cymbella saxicola Bily & Marvan, for which SEM photographs are given for the first time. The new species was found in ultra-oligotrophic waters, associated with virtually no biomass in the water column.

Diatom characteristics of the Far East siliceous organogenic deposits

Three Far East diatomites, Puzanov (Kunashir Island, Kuril Islands), Sergeevskii, and Terekhovka (Southern Primorye) are characterized in detail. Rock-forming taxa are identified (Puzanov—Aulacoseira subarctica (O. Mull.) Hawort and Stephanodiscus niagarae var. pusanovae Genkal et Cherepanova; Sergeevskii—Staurosira construens var. venter (Ehr.) Gran., Aulacoseira italica (Ehr.) Sim., and representatives of the genus Cymbella with large valves (up to 175 Jim in length); Terekhovka—Aulacoseira praegranulata var. praeislandica f. praeislandica (Sim.) Moiss.). Morphometric analysis of valves of the dominant taxa showed a low variability of valve parameters for the Puzanov diatomite and a high one for the Sergeevskii and Terekhovka diatomites. The lake environments of the diatoms forming the diatomites were reconstructed based on the elemental composition of diatom valves and the ecological structure of diatom paleocommunities. The high oxygen and low silicon concentrations in valves of the Puzanov diatomite, most likely, indicate that the diatoms were part of plankton communities formed in a large deep freshwater lake. Significant concentrations of silicon in valves of the Terekhovka diatomite, in contrast, suggest that the diatoms occurred in benthic ecotopes in a shallow lake. The age of the deposits was refined by detailed studies of Aulacoseira valves, using light and scanning electron microscopes. For example, the presence of Aulacoseira taxa of the “prae” group in the Terekhovka diatomite confirms its Pliocene age, and the presence of valves of the present species A. italica in the Sergeevskii diatomite points to its Late Pliocene age. The identified features of the diatomites permit their use in practice.

Cymbella neolanceolata sp. nov., a species formerly known as Cymbella lanceolata

The history of the genus Cymbella C. Agardh and its typification were clarified some 20 years ago, with still some concerns on the validity and identity of some of the species involved. Different specimens have been referred to under the name C. lanceolata (C. Agardh) C. Agardh, even if its basionym is Pinnularia appendiculata (C. Agardh) Schaarschmidt. Therefore, the epithet lanceolata kept on being misapplied to species in the genus Cymbella. The typification history of Cymbella confirms C. cymbiformis C. Agardh as typus conservandus. The binomial C. cornuta (Ehrenberg) R. Ross, considered as conspecific with C. lanceolatum sensu Ehrenberg, is maintained as an independent species and lectotypified. Considering that C. lanceolata sensu Krammer is distinct from C. lanceolata (C. Agardh) C. Agardh, which is accepted as a homotypic synonym of Frustulia lanceolata C. Agardh, a new species C. neolanceolata W. Silva is proposed to accommodate the Krammer material. A new nomenclatural combination C. neolanceolata var. bottnica (basyonim C. lanceolata var. bottnica Krammer) is also made.

Epilithic, Epipelic, and Epiphytic Diatoms in the Göksu Stream: Community Relationships and Habitat Preferences

ABSTRACT Community structure of benthic diatom in Góksu Stream was studied over a one year period. The presence of a total of 69 taxa was recorded in the stream. The abundance of diatom taxa recorded varied substantially among the habitat types. The genera Cymbella, Navicula, Nitzschia, and Gomphonema comprised the most species and were numerically dominant in most communities. Frequency, diversity, and similarity of diatoms varied among habitats.