Central Fultoportulae Research Articles

Epitypification and emended description of Cyclotella hubeiana, a centric diatom from Central China, with remarks on its distribution and ecology

Since its description by Chen and Zhu in 1985 from samples collected in a river and reservoir from Hubei Province (Central China), Cyclotella hubeiana has been reported from several sites in central and southern China. Only line drawings were provided with the original description and the same drawings were used in the subsequent diatom floras from China. The more recent reports of this species come from limnological studies which generally do not provide illustrations. There is therefore a need to better illustrate this taxon. As the type material could not be retrieved, new material was collected from the type locality (Xionghe Reservoir) to elucidate its ultrastructure using light and electron microscopy. The figures published by Chen and Zhu in 1985 are designed as lectotype and the new material as epitype to the lectotype. Characteristics of the valve such as the position of the rimoportula (on a costa, within the ring of marginal fultoportulae) and the absence of central fultoportulae on the valve face suggest that this species is best placed within the genus Cyclotella as presently defined. Its morphology is compared with similar species of Cyclotella and Pantocsekiella. In addition, in a study on Qiandao Lake, a reservoir from Zhejiang Province (eastern China), a large population of this taxon was found in down-core assemblages within 20 years of the reservoir being impounded. This abundant material allowed a better assessment of the size range and morphological variability of this species. Besides emending the description and validating the taxonomic status of this species, this study also discusses its ecology and distribution.

ИНТЕРЕСНАЯ НАХОДКА ЦЕНТРИЧЕСКОЙ ДИАТОМОВОЙ ВОДОРОСЛИ PANTOCSEKIELLA COMENSIS (BACILLARIOPHYTA) В ВОДОЕМАХ СРЕДНЕГО И ЮЖНОГО УРАЛА

The study of phytoplankton in the lakes of the Middle and Southern Urals (Arakul, Elovoe and Bolshie Kasli) using scanning electron microscopy made it possible to detect a small-sized species of diatoms Pantocsekiella comensis that is new for this region. The study of phytoplankton of the lakes of the Middle and Southern Urals (Arakul, Elovoe and Bolshie Kasli) using scanning electron microscopy made it possible to detect a small-sized species of diatoms Pantocsekiella comensis that is new to this region. The study of its morphology in a population from Lake Elovoe showed a coincidence of quantitative (valve diameter, the number of striae in 10 µm, the number of central fultoportulae, the frequency of marginal fultoportulae, the number of lacunae on the valve) and qualitative (valve relief, the presence and location of granules on the valve, the location of lacunae, the orientation of the slit of the rimoportula) features with those of the diagnosis of the species and literature data.

Shionodiscus karianus sp. nov. (Thalassiosirales, Thalassiosiraceae), a new planktonic diatom from the Kara Sea and notes on some morphological characters of Shionodiscus taxa

The genus Shionodiscus (Thalassiosirales, Thalassiosiraceae) includes species that have strutted processes with long inward but reduced outward extensions, a labiate process typically located on the valve face, distant from the margin. Shionodiscus species inhabit the marine environment, and the genus includes both living and fossil species. In the course of our study of plankton samples from the Kara Sea, we found specimens belonging to Shionodiscus. Based on LM, SEM, and TEM investigations, a new species, Shionodiscus karianus sp. nov., is described. This species is distinguished from others in the genus based on areola densities, as well as the fine structure and location of the rimoportula and the central fultoportula and the ultrastructure of the areolae and cingulum. In this paper, we provide a morphological description of this taxon as well as a comparison with similar taxa. Previous records of Shionodiscus species in the Russian Arctic seas are discussed. Finally, we summarize and evaluate information on the important morphological characters, such as rimoportula position and fultoportula structure, for Shionodiscus.

Morphology and phylogeny of two new Thalassiosiroid taxa (Bacillariophyceae), with two marginal rimoportulae

ABSTRACT Thalassiosira and related taxa i.e. the taxa within Thalassiosirales are among the most abundant and widespread diatoms. The vast majority have one marginal rimoportula, but very few always have two. The knowledge on Thalassiosiroid taxa in Chinese waters is restricted, and to explore the diversity, monoclonal strains were established from southern Chinese coastal waters. Morphological data were based on light and scanning electron microscopy. The D1‒D3 region of the ribosomal large subunit (LSU) and the small subunit (SSU) encoding genes were amplified to address phylogenetic relationships. Based on a combination of morphological characters and molecular analyses, two new species with two marginal rimoportulae were described, Planktoniella pulchra sp. nov. and Thalassiosira tridens sp. nov. Planktoniella pulchra is furthermore characterized by one regular ring of marginal fultoportulae between the valve face and the mantle, as well as dense ribs on the mantle. A narrow circular extension of mucilaginous material surrounds the girdle. In phylogenetic analyses, it clustered within the Planktoniella group. Thalassiosira tridens is unique in having a pronounced external tube of the central fultoportula, as well as long external tubes of the two marginal rimoportulae. Two irregular rings formed by the marginal fultoportulae are present on the mantle, and their external extensions are either open tubes or closed spines. In the SSU and LSU phylogenetic analyses, both taxa constituted their own monophyletic lineage and were well differentiated from allied species. Thalassiosiroid taxa with two marginal rimoportulae were phylogenetically closely related, but did not make up a monophyletic lineage.

Cyclotella (Bacillariophyceae) species present in sediments dating to Marine Isotope Stage 5 from Lake Chalco, central Mexico, with special reference to two new species: Cyclotella poyeka and Cyclotella tlalocii

Lake Chalco is one of the few lakes in Mexico that has a long, continuous sedimentary sequence covering the Upper Pleistocene (> 150 000 yrs). The diatom content of its lacustrine sediments includes a variety of centric species. In particular, the sediments dating to Marine Isotope Stage 5 (MIS5) were alternately dominated by four Cyclotella spp: C. meneghiniana Kützing, C. quillensis Bailey, and two new species which are described here: C. poyeka and C. tlalocii. These two new Cyclotella spp. resemble C. stylorum Brightwell, because of the presence of marginal chambers. Nevertheless, the new species from Lake Chalco have a different structure of the marginal chambers and marginal fultoportulae with three satellite pores. Cyclotella poyeka and C. tlalocii differ from each other by the relative proportion of the central area to valve face diameter, the central fultoportula arrangement, and the striation pattern. Ecological affinities of the four Cyclotella species in the MIS5 sediments from Lake Chalco are discussed based on their modern distribution (for C. meneghiniana and C. quillensis) and their fossil assemblages (for C. quillensis, C. tlalocii and C. poyeka), leading to the conclusion that C. tlalocii was a freshwater species while C. meneghiniana, C. quillensis, and C. poyeka thrived in saline conditions.

Внутривидовой комплекс Thalassiosira incerta (Bacillariophyta) из голоценовых отложений Таганрогского залива (Азовское море): Thalassiosira incerta var. strelnikovae var. nov. и Thalassiosira incerta var. fluvialis var. nov.

New data on the morphology of Thalassiosira incerta, one of the most abundant species of the genus Thalassiosira in the Holocene deposits of the Sea of Azov, are presented. New varieties, T. incerta var. strelnikovae Kovaleva et Gogorev, var. nov. and T. incerta var. fluvialis Gogorev et Kovaleva, var. nov., are described. They are orphologically similar to the type and differ mainly by the presence of a rosette of large areolae around the central fultoportulae and the areolae density on a valve.

Fascinorbis gen. nov., a new genus of Stephanodiscaceae (Bacillariophyta) from a Late Miocene lacustrine diatomite

We used light and electron microscopy to characterize a Late Miocene freshwater diatomite deposit in the Chalk Hills Formation, near Payette, Idaho, USA. The diatom assemblage from this sample was nearly monotypic, dominated by a single taxon with similarities to Lindavia bodanica (Thalassiosirales) but with several features uncharacteristic of the genus Lindavia, such as a rimoportula(e) on the valve mantle located on a costa, simple alveolar structure, and spines at the external valve face-mantle junction. A combination of other characters for this species complicate its placement into existing genera, including a lack of central fultoportulae, central area with loculate areolae with domed cribra, and a single ring of mantle fultoportulae with three satellite pores with well-developed cowlings and broad satellite pore covers. Based on this unique set of features, we have established a new genus, Fascinorbis, which appears to represent an important transitional form in the evolution of the Lindavia lineage.

Re-examination of Cyclotella lacunarum Hustedt (Bacillariophyta) from lakes in the Pamir Mountains, western China, and description of two similar Lindavia taxa collected from Tajikistan and Nepal

Originally described from a sample collected in the Pamir Mountains at the end of the nineteenth century, Cyclotella lacunarum Hustedt is a centric diatom species that is not-well defined and seldom reported in the scientific literature. Our investigations revealed that the type locality of this taxon, now referred to as Lindavia lacunarum (Hustedt) Nakov et al., is actually in western China and not in Tajikistan, as wrongly assumed previously. Light microscope (LM) and scanning electron microscope (SEM) observations of the type material and of modern material collected at the type locality allowed us to emend the description of this species. Its most remarkable character is that it possesses central fultoportulae with only two satellite pores instead of three as generally reported for similar species of Lindavia. Lindavia lacunarum was then compared to two similar populations of Lindavia collected from high elevation lakes in Tajikistan and Nepal. These two populations were originally identified as Cyclotella/Lindavia lacunarum and represent the only reported occurrences of this taxon outside its type locality. The population from Tajikistan differs from L. lacunarum by having cells of smaller size, with an almost flat valve face and has been described as a new variety Lindavia lacunarum var. karakulensis var. nov. The Nepalese population is more clearly differentiated from L. lacunarum by having a different type of colliculate pattern in the central area and significantly lower density of central fultoportulae and is therefore described as a new species, Lindavia nepalensis sp. nov.

New Species of the Genus Cyclotella (Kützing) Brébisson (Bacillariophyta) for the Flora of Russia

Until recently, about 40 modern freshwater representatives of the genus Cyclotella were known in Russia. Most of them have been recently transferred to the genera Discostella Houk et Klee, Handmannia M.Peragallo, Pantocsekiella K.T.Kiss et Ács, and to date 11 species and varieties of the genus: C. ambigua Grunow, C. atomus Hustedt var. atomus, C. atomus var. gracilis Genkal et Kiss, C. baicalensis et Meyer, C. caspia Grunow, C. choctawhatcheeana Prasad, C. cryptica Reimann, Lewin & Guillard, C. distinguenda Hustedt, C. meduanae Germain, C. meneghiniana Kützing and C. minuta (Skvortzow) Antipova are known from water bodies and watercourses in Russia. Cyclotella cryptica and C. distinguenda belong to rare species of Russian flora. The study of the species morphology was undertaken from the river mouth of the Khara River, a tributary of hyperhaline Lake Elton (Volgograd Region, Russia). Scanning electron microscopy has made it possible to estimate the variability ranges of the main diagnostic quantitative features (valve diameter, number of striae in 10 μm, number of central fultoportulae and location of marginal fultoportulae). The literature data on morphological variability of C. cryptica is limited and our studies address the shortcomings. Findings of the species in fresh water bodies of Russia and published illustrations cast doubts on the accuracy of identification of C. cryptica, and this finding in the Khara River is suggested to be the first for Russia. For C. distinguenda, the maximum diameter of the valve is specified, ranges of variability of the number of striae in 10 μm and the size of initial cells are disclosed.

К морфологии и таксономии Cyclotella rossii (Bacillariophyta)

An analysis of published data on Cyclotella rossii and С. chantaica has shown general morphological similarity and coincidence of the majority of quantitative and qualitative characters. They are valve diameter, frequency of marginal fultoportulae and number of satellite pores in them, number of central fultoportulae and number of their satellite pores, number of rimoportulae and valve relief, presence of externally colliculatelly, position of rimoportula and its fissure orientation respectively. Based on this data and priority the name С. chantaica, it is suggested to treat C. rossii as a synonym of С. chantaica and, considering the latest changes in their systematic position, expand the diagnosis of the species Pantocsekiella chantaica (Kuzmina et Genkal) K. T. Kiss, Genkal et Ács emend. Genkal.

Description of Thalassiosira secreta sp. nov. (Bacillariophyta), unique with fultoportulae hidden inside the central areola

ABSTRACT In order to explore the diversity of the genus Thalassiosira, live samples were collected from Chinese coastal waters and monoclonal strains were established. Based on the combination of morphology and molecular data of ribosomal DNA genes, a novel species, Thalassiosira secreta sp. nov. Yang Li & Y.Q. Guo, was described from the South China Sea. The most conspicuous feature of T. secreta is 5–7 fultoportulae located inside on the inner walls of the central areola. Two rings of siliceous spines are seen; one on the edge of the valve face, and another on the mantle. A rimoportula with a remarkable external tube, is positioned on the edge of the valve face, as part of the ring of spines on the valve edge. A ring of fultoportulae is located on the valve mantle, distal from the ring of spines on the mantle, with one fultoportula corresponding to each spine. The areolae on the valve face are arranged in a linear pattern. Morphologically, T. secreta resembles T. nodulolineata, T. densannula, T. nanolineata, T. incerta and T. wongii, all having several fultoportulae surrounding the central areola. This is partly supported by the phylogenetic analyses, as T. secreta clustered together with T. nodulolineata, whereas the sequences of the remaining taxa are unavailable presently. The positions of the central fultoportulae differ among the above allied taxa, as they are ‘hidden’ on the inner wall of the central areola in T. secreta, but located on the external wall of the central areola in the remaining taxa. All these morphologically related taxa may represent a new subgroup within the genus Thalassiosira, but this needs to be confirmed by molecular data. The taxa are all characterized by several fultoportulae surrounding the central areola.

Thalassiosira duostra (Bacillariophyta), a new for the flora of Russia freshwater diatom species

The study of archive materials has made it possible to specify species composition of the genus Thalassiosira and discover a new for the flora of Russia representative of centric diatoms, T. duostra, in Cheboksary and Tsimlyansk reservoirs and the Oka River. The valve diameter and number of central futoportulae in the examined material differ insignificantly from the original description and published data. By the general valve outline, structure and arrangement of central and marginal fultoportulae and quantitative characteristics, T. duostra is very similar to Сonticribra weissflogii and Thalassiosira faurii, which may result in inaccurate identification of these species. In the Сonticribra weissflogii the rimoportula is located not in a ring of marginal fultoportulae but closer to the valve center and its internal part is significantly larger than in Thalassiosira duostra. The external arrangement of marginal fultoportulae (tubes of the processes are outwardly directed at different angles) and their internal arrangement (the processes are arranged in two rings, they are more dense in the ring which is closer to the valve face) is a good specific feature that differentiates T. duostra and T. faurii.

Morphological variation around the Pantocsekiella comensis complex in the Laurentian Great Lakes

Pantocsekiella comensis is ubiquitous in the Laurentian Great Lakes and is an important indicator of climate change and low nutrients. Pantocsekiella comensis forms a diverse complex with high morphological diversity. We distinguished three species within the complex: P. comensis, Pantocsekiella delicatula, and Pantocsekiella laurentiana sp. nov. by examining specimens from the Great Lakes using light and scanning electron microscopy. All species have radial, uniform, and alveolate striae, a central fultoportula, a rimoportula opposite the central fultoportula, and marginal fultoportulae. However, P. laurentiana has a smaller diameter than P. comensis (4–8 µm vs. 4–12 µm) and orbiculi depressi on half its tangentially undulated centre. Pantocsekiella delicatula has a distinct central fultoportula and colliculate centre, and lacks the orbiculi depressi and tangential undulation of P. comensis and P. laurentiana. Its diameter (4–14 µm) is generally larger than that of P. comensis. A multiple factor analysis based on morphological features, in addition to environmental characteristics, confirmed the separation of these species. The presence of transitional specimens with features of two or more of these species complicated classification; however, these occurrences were rare, and differentiation was usually possible.

Cyclotella petenensis and Cyclotella cassandrae, two new fossil diatoms from Pleistocene sediments of Lake Petén-Itzá, Guatemala, Central America

While analyzing the fossil diatom flora in one of the longest paleolimnological records (core PI-6) from Lake Petén-Itzá, lowland Guatemala, we encountered Aulacoseira Thwaites, Cyclotella (Kützing) and Discostella (Cleve & Grunow) Houk & Klee species appearing successively in the record. Among them, two new species that are assigned to the genus Cyclotella are described herein. Cyclotella petenensis sp. nov. is characterised by a coarse striation marked by a shadow line and a tangentially undulate central area with an arc of central fultoportulae. Cyclotella cassandrae sp. nov. has an elliptically shaped valve, coarse striae and a scattered ring of central fultoportulae in the central area. Classification and differences to similar taxa in the genus Cyclotella are discussed.

Taxonomy and ultrastructure of Sinerima, a new genus of diatoms (Bacillariophyta), with a description of a new species, S. marigela

Based on light, scanning and transmission electron microscopy observations, a detailed description of a new marine fultoportulate diatom Sinerima marigela gen. et sp. nov. is presented. This new taxa is rare (<3% of the thanatocoenosis) in surface sediments in the Bering and Chukchi seas, but appears to have an association with high spring sea ice concentrations. The new monotypic genus is distinct due to its 1) lack of rimoportulae, 2) one-layer valves with marginal pseudoloculi, 3) characteristic velum composed of a cluster of short tubes, and 4) central part without either central fultoportulae or an annulus. This set of characters, especially the lack of rimoportulae, makes S. marigela unique and easily distinguishable from other fultoportulate diatoms.

Pliocaenicus bolshetokoensis – a new species from Lake Bolshoe Toko (Yakutia, Eastern Siberia, Russia)

A new species from the diatom genus Pliocaenicus Round & Håkansson is described from Yakutia (Eastern Siberia, Russia) as Pliocaenicus bolshetokoensis sp. nov., on the basis of light and scanning electron microscopy. The new species is morphologically similar to other members of the genus but differs from the closely related species, Pliocaenicus costatus (Loginova, Lupikina & Khursevich) Flower, Ozornina & Kuzmina and Pliocaenicus seczkinae Stachura-Suchoples, Genkal & Khursevich, mainly by the position of the central fultoportulae and the valve face relief. Variability of quantitative features such as valve diameter, number of striae and areolae in 10 µm, and number of central fultoportulae are similar to data known from other centric genera. The most variable quantitative character of P. bolshetokoensis sp. nov. is valve diameter; the numbers of areolae and striae in 10 µm were less variable.

Morphology and molecular phylogeny of Thalassiosira sinica sp. nov. (Bacillariophyta) with delicate areolae and fultoportulae pattern

ABSTRACTThalassiosira Cleve is one of the most species-rich marine diatom genera. Previous studies have mainly focused on polar and temperate areas, but recent studies on material from Asian waters suggested that a high and undescribed species diversity of Thalassiosira occurs in Asia. On the basis of plankton samples collected from the South China Sea, a new species, T. sinica sp. nov. Y. Li & Y. Q. Guo is described. The morphology of the cells was examined by light and scanning electron microscopy. The hypervariable region of the nuclear large-subunit ribosomal DNA and the relatively conserved region of the nuclear small-subunit ribosomal DNA were sequenced for information on phylogenetic relationships. The living cells are usually solitary and drum-shaped. The areolae on the valve are delicate, small and arranged in fascicles. In addition to a regular ring of marginal fultoportulae on the valve edge, T. sinica possesses one central fultoportula and a number of fultoportulae arranged into 2–3 irregular rings on the valve face. A rimoportula located inside the ring of marginal fultoportulae possesses a long and strong external tube. The valvocopula and the copulae have rows of pores, but the pores on the valvocopula are larger than those on the copulae. Thalassiosira sinica appears to be included in subgroup C sensu Gedde because of a rimoportula with a distinct external tube located on the valve face. The molecular phylogeny, inferred from both SSU and LSU sequences, does, however, not support the validity of subgroup C, as the closest allies of T. sinica here turned out to be T. diporocyclus and T. lundiana, species in which the rimoportulae are located on the valve margin.

Cyclotella deceusteriana, a new centric diatom species (Bacillariophyta) from the sub-Antarctic Region

During a survey of the freshwater diatom flora of the sub-Antarctic region (Iles Kerguelen and Iles Crozet) in the southern Indian Ocean, an unknown Cyclotella taxon was observed that was formerly identified as the presumed cosmopolitan C. meneghinana. Detailed morphological analysis based on light and scanning electron microscopical observations and comparison with several similar Cyclotella taxa worldwide justified the description of this unknown taxon as a new species: Cyclotella deceusteriana sp. nov. The new taxon is characterized by the presence of marginal fultoportulae on every costa, hyaline furrows between the raised marginal parts on which the striae are located, 2, occasionally 1, 3 or 4 central fultoportulae and an entirely flat, smooth, relatively small central area. The new species is described and compared with other Cyclotella taxa. Notes on its distribution and ecology are added.

A new species of nanoplanktonic diatom: Thalassiosira catharinensis (Bacillariophyceae) from Southern of Brazil

Thalassiosira catharinensis is a new nanoplanktonic diatom 4.4–6.6 µm diameter. The diagnostic characteristics are the presence of fultoportulae and rimoportulae with short external tubes of the same diameter, rimoportula located at same level as fultoportulae, the presence of three satellite pores around marginal and central fultoportulae, and rimportula with small, shallow internal aperture. The new species is compared to similar taxa such as Thalassiosira laevis, T. mala, T. minima, T. profunda and T. pseudonana.

Cytoplasmic inheritance of parent-offspring cell structure in the clonal diatom Cyclotella meneghiniana.

In cytoplasmic inheritance, structural states of a parent cell could be transmitted to offspring cells via two mechanisms. The first is referred to as the hangover of parent structure, where the structure itself remains and faithfully transmits within offspring cells; the second is structural inheritance, wherein the parent structure functions as a template for development of new offspring structure. We estimated to what extent the parent structure affects the development of offspring structure by structural inheritance, using a clone of the diatom Cyclotella meneghiniana The cell has two siliceous valves (a cell wall part at both cell poles): one is inherited from the parent and the other is newly formed. We estimated cytoplasmic heritability by comparing valve traits (central fultoportulae (CTFP), striae, central area, and cell diameter) of parent and new offspring valves, using single-cell isolation and valve labelling. Parent-offspring valve trait regressions showed that all traits, except CTFP, were significantly correlated. We formulated a quantitative genetic model considering the diatom inheritance system and revealed short-term rapid evolution compared with other inheritance systems. Diatom structural inheritance will have evolved to enable clonal populations to rapidly acquire and maintain suitable structures for temporal changes in environments and life-cycle stages.