Valve Face Research Articles

Halamphorahampyeongensis sp. nov. (Amphipleuraceae, Bacillariophyceae), a new marine benthic diatom from a tidal mudflat in Hampyeong Bay, South Korea.

The abundance and variety of benthic diatoms inhabiting tidal flats is widely acknowledged, although it has received relatively less attention than other research areas. In this investigation, we provide a formal description of a benthic diatom found in the tidal mudflat of South Korea, based on morphological and molecular characteristics and the similarities and differences between Halamphorahampyeongensis sp. nov., with morphologically similar Halamphora species are also discussed. Morphological characteristics are described from light and electron microscopy images. H.hampyeongensis is distinguished by its wide ventral sides of the valve, small and rounded areolae present across the whole valve face, and dense dorsal striae biseriate (34-38 in 10 μm). Phylogenetic analysis based on 18S rDNA and rbcL sequence data revealed that H.hampyeongensis is related to H.montana, H.mosensis, and H.specensa. The results (morphometric and molecular) provide sufficient elements to support and propose this taxon as a new species.

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.

Lutophila gen. nov., a new diatom genus from the hottest place on Earth, Lut Desert, Iran

The Lut Desert is one of the world’s driest and hottest large deserts. This large basin has shallow groundwater pools that have been studied little for microbial flora, especially diatoms, and the present study is the second attempt. We report a new genus with one new species and the related morphotypes. The genus Lutophila and its type species L. iranica is found in hypersaline pools and a saline river in the Central Lut Desert depression, an area known as the hottest spot in the world. The morphology, systematic position, distribution, and ecological conditions of the new species and its morphotypes are discussed. The new genus Lutophila has a linear-lanceolate, symmetric outline with broadly rounded apices and two kinds of areolae, one on the valve face and one on the valve mantle; these characters resemble those shared by the diatom genera Krasskella, Biremis, Chamaepinnularia and Oestrupia. Lutophila iranica exhibits two morphotypes with similar outline; however, L. iranica morphotype 2 is wider than the L. iranica morphotype 1 and has a more distinctive central area.

The Search for Species Flocks in Marine Benthic Homoeocladia spp. (Diatomeae: Bacillariales). I. Variations on Three Themes, Seventeen New Species

Exploration of the diversity in the diatom genus Homoeocladia across Micronesia revealed several clusters of undescribed species based on variations around several characters. Using ultrastructural data from scanning electron microscopy, we describe seventeen new species in three of these morphological groups. (1) A group with external thickenings includes eight new species with costae and/or bordered areolae on valve face and/or conopea and/or peri-raphe zone, and one with similar areolae but no ornamentation; this group includes the previously described H. jordanii. (2) Large, linear species, resembling H. asteropeae and H. tarangensis; we describe three new species close to the latter. (3) A sinuous-areolae group includes five new species with areola openings shaped like “~”, “s”, or “z” on the valve and/or girdle bands, or both, and leads to reconsideration of the diagnosis of Homoeocladia schefterae and the recognition that the globally widespread species in this complex is H. coacervata sp. nov. The three groups are based solely on morphology and no genetic relationships are implied within or between the groups, other than having the characteristics of the recently redefined genus Homoeocladia. However, the high diversity of species in Homoeocladia suggests the genus is a good candidate to test for species flocks in this region and in at least one other comparable location, incorporating DNA sampling through either culturing or metabarcoding.

Taxonomic revision of Coscinodiscus variabilis (Bacillariophyta): analysis of type material, lectotypification and transfer to the genus Actinocyclus

The centric diatom Coscinodiscus variabilis, described by Joaquín Frenguelli for the coastal waters of Mar del Plata City (Buenos Aires, Argentina), was examined to review and elucidate its taxonomic position. The type material contained in the Frenguelli Collection was studied with light microscopy. The species has a particular and distinctive stellate pattern of hyaline rays on the valve face that helps in its initial identification and exhibits a remarkable morphological variation. The presence of a distinctive pseudonodulus, radial sectoring and circular valves support its transfer to the genus Actinocyclus as Actinocyclus ferrarioae nom. nov. The valve morphology of A. ferrarioae is described and compared to its original description and closely related taxa. We have estimated the rimoportulae density as a morphometric character for comparing morphologically similar Actinocyclus taxa. Since Frenguelli did not formally designate a holotype in the original description, we selected a lectotype and provide an expanded description of the species.

Three New Nitzschia (Bacillariophyceae) Species from Highly Acidic Artificial Lakes in Çanakkale, Türkiye

Çanakkale is located in Western Anatolia, a region known for extensive mining in the country. In this study, three new species: Nitzschia arslaniana sp. nov., Nitzschia efeiana sp. nov., and Nitzschia szaboiana sp. nov. are described from highly acidic environments in Çanakkale. In morphology, Nitzschia arslaniana is similar to Nitzschia inconspicua but Nitzschia inconspicua is broader, with a lower fibulae density. Nitzschia efeiana is similar to Nitzschia. bremensis, Nitzschia capitellata, Nitzschia homburgiensis, Nitzschia hybrida, Nitzschia palustris, and Nitzschia pellucida. However, Nitzschia efeiana has variable fibulae widths, thickened virgae on its external valve face, and an elevated ridge on the valve margin opposite the keel. Nitzschia szaboiana is similar to Nitzschia pusilla, but the later taxon has a higher striae density. This study highlights the unique species diversity of extreme environments, including anthropogenic extreme environments, by describing three new taxa in the same genus.

Craspedostaurosnazmii sp. nov., a new diatom species (Bacillariophyta) from the Turkish Coast of the Black Sea.

Craspedostauros E.J. Cox is a diatom genus comprising 17 taxa reported from various regions of the world. While many species of Craspedostauros are epibiontic, the taxa have variable ecological preferences. In this study we formally describe Craspedostaurosnazmiisp. nov., an epilithic species discovered along the Turkish Black Sea Coast, based on light and scanning electron microscopy. Craspedostaurosnazmiisp. nov. is characterized by valves that are lanceolate to narrowly lanceolate, slightly constricted near the apices with uniseriate, parallel throughout the whole valve, transapical striae and and the presence of an apical silica flap. The areolae are distributed over the valve face and the mantle. The differences and similarities between C.nazmiisp. nov. and established species of Craspedostauros are discussed. Based on shape and morphometrics, the most similar species is Craspedostauroscapensis, but it is easily distinguished from C.nazmiisp. nov. by its lack of an apical silica flap.

Taxonomy and phylogeny of Chaetoceros species of the section Stenocincta (Bacillariophyceae), with emendation of C. affinis and C. willei and description of three new species

ABSTRACT Species of Chaetoceros sect. Stenocincta are frequently observed in marine phytoplankton. To study species diversity within the section Stenocincta, monoclonal strains were established from Chinese coastal waters and Norwegian Sea. Following detailed morphological observations and molecular evidence inferred from nucleus-encoded large subunit ribosomal DNA, the descriptions of C. affinis and C. willei are emended based on isolates from their respective type localities. Additionally, three new species are described. Chaetoceros donghaiensis sp. nov. is characterized by short straight chains, with thin setae only, and terminal setae that tend to cross distally. Chaetoceros forceps sp. nov. is unique by its thick terminal setae, each with an inflation near the end, with each pair forming a V-shape, resembling forceps. Chaetoceros lepidus sp. nov. is characterized by short, straight chains, narrowly elliptical valve faces, setae all located in the apical plane, and arched intercalary setae in opposite directions to the chain axis in broad girdle views. Three other distinct clades, which may also represent new species, were discerned in the LSU rDNA phylogeny, but more morphological characters are needed before formal proposals can be made. These species/clades formed a well-supported monophyletic lineage, supporting the current circumscription of section Stenocincta. This section is characterized by colonies in straight chains, cells with one chloroplast only, narrow lanceolate apertures, and terminal setae generally thicker than intercalary ones or both similar and thin. However, in C. diversus the terminal setae are thin and distinctly thicker pairs of intercalary setae are usual.

Abrasive wear resistance of Fe3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_{{3}}$$\\end{document}Al and Stellite 6 coatings for the protection of valve faces

Developing a technology that increases the service life of valve seats in CNG/LNG-powered vehicles requires the appropriate selection of material and its application technology. Commercially used valve seat materials show accelerated wear under operating conditions, especially in natural gas vehicle engines. The authors developed a new material and technological concept to protect the valve seat in CNG/LNG-powered vehicles. Two materials were used in the research: Stellite 6 alloy and Fe3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_{3}$$\\end{document}Al intermetal. A commonly used material for valve seats of combustion engines is Stellite 6. The Fe3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_{3}$$\\end{document}Al is the new proposed material coating for the protection of the valve seats of internal combustion engines. The article compares the abrasive wear resistance of these materials. The abrasion tests were performed on a T-11 pin-on-disc tester, and the counter-sample was steel S235JR. The test conditions were similar to those prevailing during the operation of the valves in the head of the internal combustion engine, without the influence of temperature. The results indicate that the Fe3Al intermetallic compound is characterised by a lower coefficient of friction and wear intensity than Stellite 6. The results of exploitation tests confirm that the Fe3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_{3}$$\\end{document}Al phase is a prospective material to be used as a protective material on the valve seat of vehicles. The authors made a mathematical model for the wear of the newly created surface layers and proposed hypotheses regarding the wear mechanisms of these layers.

Orthoseira groenlandica sp. nov., a new aerophilic diatom (Orthoseirales, Bacillariophyta) species from Greenland

During the survey of the moss-inhabiting diatoms in samples from Greenland, an unknown Orthoseira taxon was observed that was originally identified as O. roeseana but differed from the recently published lectotype population of the latter. Comparison with all known Orthoseira taxa worldwide showed that the unknown taxon represented a new species that is described as O. groenlandica, sp. nov. based on detailed light and scanning electron microscopy. The combination of the unique, rather chaotic valve face and mantle surface ornamentation, the absence of caverns and marginal pore fields, the presence of robust, short spines, and the absence of chain-like colonies has not been observed so far in any known Orthoseira species. The morphology of the new species is discussed comparing it with the morphology of all other Orthoseira species worldwide by carefully analysing the different morphological features observed so far in members of the genus Orthoseira. Brief notes on the ecology of the sample where the new species was found are added.

Morphological and molecular characterization of twenty-five new Diploneis species (Bacillariophyta) from Lake Tanganyika and its surrounding areas

Lake Tanganyika, the second oldest lake in the world, is home to some of the largest and most phenotypically, genetically, and ecologically diverse freshwater assemblages. While the evolutionary processes responsible for generating its extraordinary richness are well understood across various animal groups, little is known about the diatom species richness, turnover patterns, and their drivers. Here, we explored species richness of the diatom genus Diploneis from Lake Tanganyika and surrounding regions by using morphological and molecular information. Both datasets suggested the presence of twenty-five new Diploneis species, each not related to any known Diploneis species so far. The multi-locus phylogeny indicates a monophyletic group of twenty-one Diploneis species from Lake Tanganyika, suggesting potential intralacustrine diversification possibly triggered by certain historical contingencies. This is supported by the small genetic distances and the presence of unique silica ornamentations on the valve face exterior, to date only known to occur on the Baikal endemic Diploneis implicatus. The discovery of such a high richness of Diploneis species in Lake Tanganyika and the presence of a unique morphological character points to a potential adaptive radiation - a mechanism yet to be confirmed.

Ultrastructure of four Surirella taxa (Bacillariophyceae) from Qinghai Province, northwest China, with reference to the characteristics of portulae

During our investigations on the freshwater diatoms from Qinghai Province, China, four sympatric Surirella taxa belonging to the group Pinnatae were analysed. Based on morphological observations derived from light and scanning electron microscopy, three of these four taxa were identified as: S. minuta, S. lacrimula, and S. brebissonii var. kuetzingii. The fourth taxon is described as Surirella liubingii sp. nov., a new species with a unique combination of characteristics. These include the distribution pattern of its costa-stria bundles (CSBs) alternating with its over-fibula costae (OFCs), which is formed by the distinctly elevated CSBs on the valve face, mostly composed of three costae, and OFCs with a remarkedly lower position. Other characteristics include the presence of robust fibulae extending to the valve midline, the presence of only one portula between two adjacent fibulae, and a “pseudoseptum” extending internally from the valve margin. From the observations on these four Surirella taxa, we described and discussed two types of fibula (one in which the fibula nearly reaches the valve midline and one with short fibula) and two types of portula morphology (one with only one portula between two adjacent fibulae and the other with 2–4 portulae between two adjacent fibulae).

Nitzschia venerata, sp. nov., a simulacrum for the conopeate, tube-dwelling diatom Nitzschia martiana, has scuta not conopea: a case of convergent evolution?

Abstract Nitzschia martiana, recently restored to Homoeocladia (C. Agardh) emend Lobban et Ashworth, has needle-like cells and forms macroscopic colonies that are so distinctive that they have been reported on the basis of light microscopy alone. It is the type species for Homoeocladia, which have long flaps (conopea) arising from the sternum and covering a valve depression. This group has extreme diversity at the ultrastructural level and it would not be surprising to find another similar to H. martiana. However, Nitzschia venerata, sp. nov., is a surprising look-alike found in a coral reef seaweed sample from Saipan, Northern Mariana Islands (Western Pacific Ocean). It was studied with light- and scanning electron microscopy. Attempts to find colonies in live and preserved samples were unsuccessful. It is very long and narrow, with a valve depression like that in conopeate species. However, ultrastructurally it is not conopeate because the long flaps arise from the valve face and grow toward the keel and can therefore be classified as scuta. Although tube formation remains unknown, the extreme length and narrowness of the cells suggest it might occur, so that scientists identifying potential H. martiana should be alert to the possibility that they have N. venerata or some other needle-like Homoeocladia.

Halamphora minima (Catenulaceae, Bacillariophyta), new brackish diatom species from the mudflat in Hampyeong Bay, Korea

The diversity of benthic diatoms living in the tidal flats is thought to be very high but has been somewhat marginalized from our main concern. We propose a new species, Halamphora minima sp. nov. isolated as monoclonal cultures from a tidal mudflat based on light and scanning electron microscopy and molecular analysis. This species is the smallest known species of the genus Halamphora to date. Other main characteristics that distinguish this species are the biseriate separated by strongly developed costa for the majority of the valve face, and density of dorsal striae. Phylogenetic analysis of the chloroplast ribulose bisphosphate carboxylase large chain gene showed that H. minima seems to be related to H. foramina, H. sydowii and H. tumida, but the phylogenetic location of H. minima was not clear due to the low bootstrap.

Paralia flatoniana sp. nov., a new species from the late Eocene of Texas with discussion on ecology and initial valves

A new Paralia Heiberg species, Paralia flatoniana sp. nov., is documented from a late Eocene diatomite and mudstone deposit in east central Texas. Paralia represents up to 63% of the assemblage in the diatomite samples and 34% in the mudstone. Numerous Paralia initial valves are present adding an unusual component to this assemblage as they are infrequently reported from samples containing populations of fossil Paralia. A third valve type observed attached to Paralia chains is also illustrated and discussed. Intact chains are common and preservation of the frustules is very good with limited indication of dissolution or transport. An average valve diameter of 19.0 µm (7.1–37.7 µm range), the presence of numerous initial valves and preservation of fine morphological structures suggest an environment with often high in situ productivity rather than a transported assemblage. Morphologically similar species Paralia crenulata and Paralia thybergii share many mantle characteristics with P. flatoniana while the valve face details of Paralia fausta are similar. Paleogeography and – ecology of the Eocene Gulf of Mexico and volcanism to the west provided a temperate coastal nutrient-rich shelf environment favourable for Paralia.

A new marine epipsammic diatom species, Ambodajingensis sp. nov. (Bacillariophyceae), from the coast of Southeast China.

Ambodajingensis HH Liu, Z Wang, YH Gao & CP Chen, sp. nov. is described as a new species in samples collected from sand grains at Dajing Beach, Ningde City, Fujian Province, China. Morphological details of the new species with respect to valve shape, size and valve ultrastructure are presented based on light microscopy (LM) and scanning electron microscopy (SEM). The main features of Ambodajingensis under a light microscope are elongated elliptic valves with rounded apices, two internal costae on the valve and rectangular in girdle views. SEM observation showed that externally, the frustules are comprised of two valves with a relatively deep mantle and a transition between the valve faces. Small, flabelliform spines are present along the valve margin. Internally, the valves are divided into three sectors by robust costae, which penetrate the whole valve lumen and are thickest at the mantle interior and thinner toward the center. The sternum is narrow and linear, visible only in the valve apex, set off by costae. The striae are comprised of small, round areolae and they are parallel in the middle to slightly radiate at the apices. The new species is compared with other species in the genus Ambo.

Planoplatessa gen. nov.-A New, Neglected Monoraphid Diatom Genus with a Cavum.

A new monoraphid diatom genus, Planoplatessa gen. nov., is described on the basis of a detailed morphological investigation using light and scanning electron microscopy. We transferred Achnanthes joursacensis Héribaud, a species described from fossil deposits in France, to our new genus. We investigated material from Mongolia from Recent populations. This taxon is known from fossils to Recent across the Holarctic. Achnanthes joursacensis was previously transferred to the genera Planothidium and Platessa, but the morphology of A. joursacensis does not share all morphological features with these two genera. We discuss important morphological features for the delimitation of monoraphid genera based on careful morphological and molecular investigations we presented previously. Planoplatessa gen. nov. as a genus is characterized by having uniseriate striae on both the raphe and the rapheless valves, a cavum in rapheless valves only, and straight distal raphe ends on the valve face.

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.

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.

Aulacoseira newjerseyana sp. nov. (Bacillariophyta) a new freshwater centric diatom species from the northeastern USA

A new species of Aulacoseira Thwaites is described from sediment deposits of Surprise Lake, an isolated lake located in the New Jersey Highlands. The species is characterized by (1) a low mantle, (2) unevenly distributed mantle areolae of variable size and shape, and (3) a valve face covered by rounded areolae. The new species is most similar to Aulacoseira biseriata (Grunow in Van Heurk) Houk, R. Klee & H. Tanaka. Both taxa possess frustules with mantles that are low, with irregular pervalvar rows or scattered areolae. However, the two species differ in the shape and pattern of the areolae, the shape and structure of the mantle wall, the shape and depth of the ringleist, and other morphological features. In this study, we present light and scanning electron microscopic images of the new species and compare it to the most similar taxa.