Marginal 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.

A new freshwater species Conticribra sinica (Thalassiosirales, Bacillariophyta) from the lower reaches of the Yangtze River, China

A new freshwater diatom species Conticribra sinica sp. nov. Yu, You et Wang from three lakes in the lower reaches of the Yangtze River, China, is described here using a combination of morphological and molecular data from ribosomal DNA genes. The primary distinguishing characteristic of C. sinica was the presence of a non-plicate or slightly-plicate valve face and a single ring marginal fultoportulae that was located at the junction between the valve face and the mantle. There were 4-11 valve face fultoportulae that were located at the subcenter of the valve face. In addition, a single rimoportula replaced a marginal fultoportulae. Areolae loculate were open to the outside by irregularly circular foramina or slit foramina that are radially arranged. Internally, cribra were continuously arranged long a radial arrangement of areolae. Characteristics of the new species with other similar species of Conticribra. Phylogenetic analysis of the nuclear small subunit (SSU) rDNA sequences and nuclear large subunit (LSU) rDNA gene sequences revealed that C. sinica in a single clade at a considerable sequence distance from the other Conticribra species.

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.

Diversity and emendation of the genus Planktoniella (Bacillariophyceae), with descriptions of P.tubulata sp. nov. and P.trifurcata sp. nov.

For the first time, LSU and SSU sequences were obtained from four species of the marine planktonic diatom Planktoniella. Samples were collected and cultured from Chinese coastal waters, and morphological observations were made using light and scanning electron microscopy. Combined morphological and DNA sequence data revealed two new species herein described as Planktoniella tubulata and Planktoniella trifurcata. Planktoniella tubulata is characterized by the prominent external tubes of two rimoportulae and the long external tubes of the marginal fultoportulae. The latter are organized regularly in a ring, externally on the mantle, and protrude parallel to the valvar plane. Planktoniella trifurcata is unique in having mucilaginous extensions that usually expand into three lobes, and external extensions of the marginal fultoportulae being either tubes or spines. In the phylogenetic analyses inferred from SSU and LSU sequences, the four analyzed Planktoniella taxa formed a well-supported monophyletic group. A suite of three characters, mucilage membranes or wings, two marginal rimoportulae, and mantle ribs are diagnostic for Planktoniella. Based on these detailed ultrastructural observations, the description of Planktoniella is emended.

New fossil genus and new extant species of diatoms (Stephanodiscaceae, Bacillariophyceae) from Pleistocene sediments in the Neotropics (Guatemala, Central America): adaptation to a changing environment?

Several taxa of Stephanodiscaceae were found in the upper section of Pleistocene sediments from Lake Petén-Itzá (Guatemala). A new fossil genus Cyclocostis Paillès gen. nov. and new extant species Discostella gabinii Paillès & Sylvestre sp. nov. are described. Cyclocostis gen. nov. is characterized by a strongly tangentially undulated valve surface, coarse unequal striation reaching a central punctum in the valve center, an absence of central lamina and domed criba, widely open alveoli with one median recessed costa bearing marginal fultoportulae and a single rimoportula all within a ring. A single valve face fultoportula is present on the raised part of the valve opposite the rimoportula. Differences relative to similar genera and the delimitation of a new genus are discussed. Discostella gabinii sp. nov. is distinguished by circular and flat valves, a small central area bearing 5 to > 30 scattered large areolae giving a colliculate appearance, medium-sized alveoli, marginal fultoportulae on every 4–5th costa, a single rimoportula and internally smooth valve center. Differences to similar taxa in the genus Discostella are discussed. The succession of the species of Cyclotella, Discostella and Cyclocostis gen. nov. in our record could represent eco-phenotypic responses to particular environmental stress / change.

Tertiarius minutulus sp. nov. (Stephanodiscaceae, Bacillariophyta) – a new fossil diatom species from Lake Ohrid

A new fossil diatom species, Tertiarius minutulus sp. nov., is described from a sediment sequence DEEP-5045-1 of Lake Ohrid. The species is characterized by small valves (3.0–8.0 µm) with a round shape, a marginal area with radially arranged costae and a central uneven area with scattered areolae. Externally, the alveoli are occluded by cribra perforated by irregularly arranged pores. Internally, the alveoli are simple and areolae are occluded with domed cribra. The marginal fultoportulae are situated on costae close to the valve margin, located on every 5th or 7th thick internal costa. One to three fultoportulae are present on the valve face, each surrounded by two to three satellite pores. One rimoportula is present, positioned on a costa at the valve face / mantle junction. The species is compared with morphologically similar taxa and a detailed differential diagnosis is provided. Tertiarius minutulus sp. nov. is known only as a fossil taxon from Lake Ohrid, with a first occurrence during the early stages of lake basin development.

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.

К морфологии и таксономии Cyclotella distinguenda (Bacillariophyta)

The study of morphology of Cyclotella distinguenda from the karst Lake Klyuchik (Nizhny Novgorod Region) revealed that several quantitative characters (such as valve diameter and the number of marginal fultoportulae) demonstrated more variability in that species as compared to published data. Among the investigated characteristics, valve diameter (variation coefficient CV = 34.5%) and number of marginal fultoportulae (CV = 31.5%) were the most variable. The number of striae in 10 μm (CV = 10.0%) was the least variable character. For the first time, during the investigated period of massive growth of that species in the lake, the presence of initial valves was revealed. C. distinguenda can be characterized as cryophilic halophilous taxon which prefers sulphate-hydrocarbonate and neutral to light alkaline waters.

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.

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.

Two new fossil Cyclotella (Kützing) Brébisson species from Lake Ohrid, Macedonia/Albania

Lake Ohrid is the oldest existing lake in Europe and it is known for its high diversity with around 200 endemic or relict diatom species recognized. In order to understand this phenomenon, a large project on deep drilling was performed and a core with maximum sediment depth of 569 m which spans > 1.2 million years was recovered. Two new species of Cyclotella were discovered in the core samples, which are described here as Cyclotella cavitata sp. nov. and Cyclotella sollevata sp. nov. The species have been studied with light and scanning electron microscopes, their morphological features and their relevance to other members of the genus Cyclotella are discussed. Cyclotella cavitata sp. nov. is characterized by round to elliptical shape; elliptic and tangentially undulate central area with one to three papillae on the elevated side. Central fultoportulae are absent while marginal fultoportulae internally are located on slightly depressed costae, with short tube openings with two satellite pores surrounded by cowlings. Satellite pores are situated circumferentially. Internally the rimoportula is situated in the marginal area with a sessile labium. Cyclotella sollevata sp. nov. is characterized by round valves with convex or concave central area which is uneven, colliculate, with papillae and granules. Central fultoportulae are present with variable number (9-21), internally with short tube openings with two satellite pores, which are surrounded by cowlings; Internally marginal fultoportulae are located on depressed costae and have short tube openings with two satellite pores situated circumferentially, surrounded by cowlings. The rimoportulae are located in the marginal area with a sessile labium variably orientated. Cyclotella sollevata and Cyclotella cavitata have been observed only in the fossil sediments of Lake Ohrid. Comments on the position of rimoportula, used as synapomorphic character to separate Lindavia from Cyclotella sensu lato are provided.

New freshwater diatom genus, Edtheriotia gen. nov. of the Stephanodiscaceae (Bacillariophyta) from south‐central China

SUMMARYWe describe a new genus and species of the diatom family Stephanodiscaceae with light and scanning electron microscopy from Libo Small Hole, Libo County, Guizhou Province, China. Edtheriotia guizhoiana gen. & sp. nov. has striae across the valve face of varying lengths, and are composed of fine striae towards the margin and onto the mantle. Many round to stellate siliceous nodules cover the exterior of the valve. External fultoportulae opening are short tubes; the opening of the rimportula lacks a tube. Internally a hyaline rim is positioned near the margin. Marginal fultoportulae possess two arcuate opercles. Areolae have domed cribra on the valve face. Those near the margin do not open to the interior. One to three sessile to slightly‐raised rimportulae are placed on the valve face towards the margin; they do not terminate shortened striae towards the center of the valve. This suite of features distinguishes this group from other known genera in the Stephanodicaeae. Cyclotella shanxiensis is transferred to Edtheriotia, making the new combination E. shanxiensis (Xie & Qi) Kociolek et al. comb. nov. It differs from E. guizhoiana by the presence of open pores near the margin of the valve. Features of the new genus are compared and contrasted with others in the Family Stephanodiscaceae. The two species of the genus, unlike most in the family, are known only from rivers and ponds from China and Japan.

Morphological study of Cyclotella distinguenda with a description of a new fossil species Cyclotella paradistinguenda sp. nov. from the Agios Floros fen, SW Peloponnese, Greece in relation to other Cyclotella species

In a previous palaeoenvironmental study based on a high-resolution diatom record from a core sampled at the Agios Floros fen, SW Peloponnese, Greece, Cyclotella distinguenda was reported as exhibiting two morphs with distinct central area and stria arrangement, as well as a specific distribution throughout the sequence. In the present paper, we examine this morphological variability through detailed observations using light and scanning electron microscope combined with a simple statistical approach. Our new data suggest that the two morphs present substantial and constant differences in the structure and size of their central areas, the structure and number of their striae, the arrangement of their marginal fultoportulae/density of costae between fultoportulae, the shape of their rimoportulae and their alveolar chambers. On the basis of these morphological and stratigraphic variations one morph is described as a new species, Cyclotella paradistinguenda sp. nov., while the other is assigned to C. distinguenda and is also consistent with the original description of this taxon. The two species share well-defined central areas without fultoportulae, almost equal length striae and one rimoportula situated on a costa within the ring of marginal fultoportulae. Cyclotella paradistinguenda sp. nov. can be distinguished by a combination of the following characteristics: (1) large central area (≤1/3 of valve diameter), smooth or decorated with puncta and depressions, flat or concentrically undulated, (2) distinct, narrow striae (12–15/10 µm) consisting of one or two short rows of areolae of the same size expanding into three rows at the mantle, (3) marginal fultoportulae on each first to third costae (4) poorly developed alveolar chambers and rimoportula. Based on the stratigraphic distribution and the associated flora in the Agios Floros sequence, it can be inferred that C. paradistinguenda sp. nov. is tolerant of shallower water conditions with lower nutrient availability and/or higher pH than C. distinguenda.

Cyclotella paleo-ocellata, a new centric diatom (Bacillariophyta) from Lake Kinneret (Israel)

Large, subfossil populations of an unknown centric, planktonic diatom were observed in a lake sediment core from Lake Kinneret (Israel), which is here described as Cyclotella paleo-ocellata sp. nov. The new taxon, which belongs to the Cyclotella ocellata species complex, is described and separated from other similar taxa (e.g., Cyclotella ocellata, Cyclotella kuetzingiana, Cyclotella polymorpha, Cyclotella paraocellata) based on a combination of the following morphological characters: valve diameter, number of orbiculi depressi (circular depressions), number of striae/10 µm, stria length, number and position of rimoportulae and the number of central and marginal fultoportulae. Cyclotella paleo-ocellata can be distinguished mainly by two prominent characteristics: (1) the number and the arrangement of the orbiculi depressi (4-8) which increase with the valve diameter and (2) the marginal fultoportulae, situated on each, every second or third costa. Since Cyclotella paleo-ocellata is at present only known from the subfossil bottom sediments of Lake Kinneret, its ecological preferences are inferred simply from the associated diatom flora.

A new gelatinous colony-forming Thalassiosira minicosmica sp. nov. (Bacillariophyta) from Korean coastal waters and a consideration of the Thalassiosira subtilis group

A new, convex-valved Thalassiosira species, T. minicosmica, was observed from Korean coastal waters between 6 May 2009 and 6 March 2014. Thalassiosira minicosmica was characterized by: (1) gelatinous colony formation by mucilage threads extruded from the fultoportulae, (2) eccentric arrangement of the areolae, (3) almost occluded foramina, (4) a short external tube of marginal fultoportulae, and (5) a single rimoportula (with a remarkably long external tube) between marginal fultoportulae. Similar species, such as T. minuscula, T. diporocyclus and T. subtilis, were compared with T. minicosmica, and their several shared characters, such as the convex valve, foramen structure and an externally larger rimoportula than fultoportula, are diagnostic for the Thalassiosira subtilis group, rather than the gelatinous colony-forming feature. Based on the morphological similarities, we recognize the Thalassiosira subtilis group including seven Thalassiosira species.