Valve Face Research Articles

Kulikovskiyia gen. nov. (Bacillariophyceae) from the lateritic rock pools of the Western Ghats, India and from Hainan Province, China

ABSTRACTA new triundulate naviculoid diatom genus is described from the Western Ghats of Peninsular India and Hainan Province, China. The new taxon, Kulikovskiyia gen. nov. has robust conical spines along its margin and at the apices and the external valve face has longitudinally‐oriented siliceous slat system extending the length of the valve. The external distal raphe ends bifurcate and terminates on the valve face. There appear to be superficial similarities between this Asian genus and species and Playaensis, a genus comprised of two species found only in the western USA. The systematic position of Kulikovskiyia is discussed, and other than noting its similarities to other biraphid naviculoid diatoms due to symmetry features and the position of the raphe, we are uncertain about its systematic placement at finer levels of classification.

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.

Formation of extracellular β-chitin nanofibers during batch cultivation of marine diatom Cyclotella sp. at silicon limitation

Diatoms are unicellular algae that make nanostructured biosilica shells called frustules possessing ordered pore arrays. Dissolved silicon (Si) in the form of Si (OH)4 is the required substrate for cell wall biosynthesis and cell division. The extracellular formation of β-chitin nanofibers by the centric diatom Cyclotella sp. was followed during batch cultivation of the cell suspension within a bubble-column photobioreactor at a low initial Si concentration (0.25 mM) leading to 1–2 cell divisions, and high Si concentration (1.7 mM) leading to 4–5 cell divisions. Fibers were excreted from 20 specialized pores (fultoportulae) lining the rim of each frustule valve face. In Si-limited batch cultivation, 80% of the fibers formed during the last cell division after dissolved Si was depleted from the medium. Within 24 h after the final cell division, fibers were nominally 56 nm diameter and 60 μm length, with 85% of the fibers between 20 and 80 μm, and one fiber per fultoportula was formed. After the final cell number density was maintained for 72 h, a second fiber per fultoportula was formed, presumably after breakage or scission of the first fiber from the cell. X-ray diffraction (XRD) analysis confirmed that isolated fibers were composed of pure β-chitin. The unprecedented length and purity of the β-chitin nanofibers suggest future advanced material applications.

Aulacoseira giraffensis (Bacillariophyceae), a new diatom species forming massive populations in an Eocene lake

Background and aims – Diatoms began to inhabit freshwater by at least the Late Cretaceous, becoming well established by the early to middle Eocene. Aulacoseira, an important diatom in numerous ponds, lakes and rivers today, was one of the earliest known genera to colonize freshwater ecosystems. Members of this genus with characteristics familiar to those found on modern species became increasingly more abundant by the Eocene, and continued to thrive throughout the Miocene to the present. We describe a new species of Aulacoseira from an early to middle Eocene site near the Arctic Circle in northern Canada.
 Methods – Twelve samples taken from the Giraffe Pipe core were analysed in this study. Light and scanning electron microscopy were used to document morphological characters. Morphometric measurements were made from 200 specimens per sample (n = 1200), and used to investigate changes in valve size over time.
 Key results – The new species, Aulacoseira giraffensis, has valves with a length:width ratio close to 1, a hyaline valve face, straight mantle striae, a shallow ringleiste, branched linking spines, concave-convex complementarity on adjacent valve faces, and rimoportulae with simple papillae-like structure. The suite of characters, especially the highly branched spines, concave-convex valves and simple rimoportulae, is unique for this species. Large numbers of A. giraffensis specimens were found over a ten-metre section of the core, representing thousands of years. These high concentrations are indicative of abundant, bloom-like, growth.
 Conclusions – The locality represents one of the earliest known records of Aulacoseira dominating a freshwater community. Findings confirm that the morphological body plan for the genus was well established by the Eocene. Although findings indicate evolutionary stasis in morphological structure for A. giraffensis over a time scale of thousands of years, oscillations in valve morphometrics could potentially be used to trace changes in the environment of this ancient Arctic waterbody.

Taxonomy and diversity of a little-known diatom genus Simonsenia (Bacillariaceae) in the marine littoral: novel taxa from the Yellow Sea and the Gulf of Mexico

Background and aims – The diatom genus Simonsenia has been considered for some time a minor taxon, limited in its distribution to fresh and slightly brackish waters. Recently, knowledge of its diversity and geographic distribution has been enhanced with new species described from brackish-marine waters of the southern Iberian Peninsula and from inland freshwaters of South China, and here we report novel Simonsenia from fully marine waters.
 Methods – New isolates of Simonsenia species were obtained from marine waters, the littoral zone of the Korean Yellow Sea coast and the Gulf of Mexico in Corpus Christi (Texas), and documented in LM, SEM and with DNA sequence data (plastid-encoded rbcL and psbC). Phylogenetic trees of raphid diatoms were constructed to assess the relationships of the new species and of the genus as a whole.
 Key results and conclusions – Two novel species of Simonsenia (S. eileencoxiae and S. paucistriata) are described and a further putative taxon is characterized morphologically. The molecular phylogeny of the new Simonsenia species and previously sequenced species supports both the monophyly of the genus and its place within the Bacillariaceae. The Simonsenia clade clusters with clades composed of Cylindrotheca, Denticula and some Nitzschia spp. (including N. amphibia, N. frustulum, N. inconspicua). Hence Simonsenia is firmly positioned within the Bacillariaceae by molecular phylogenies, confirming its position within this group based on the possession of a canal raphe and its ultrastructure, and rejecting its classification within the Surirellaceae. Morphological data from the new Simonsenia species is typical for the genus, with a “simonsenioid” canal raphe type supported over the valve face with fenestral braces, alar canals connecting the canal raphe with the cell lumen, and the presence of fenestrae between the alar canals externally. Our results indicate unequivocally that the biogeography and the biodiversity of Simonsenia remain highly underestimated.

On the identity of Navicula gottlandica (Bacillariophyta), with the description of two new species Navicula eileencoxiana and Navicula bergstromiana from the Australo-Pacific region

Background and aims – During the past two decades, the subantarctic diatom flora has been the subject of several detailed taxonomic revisions, resulting in the description of a large number of new species. During a survey of the freshwater diatom flora of Macquarie Island (southern Pacific Ocean), an unknown Navicula species was observed showing resemblance to Navicula gottlandica. Populations of similar diatoms (previously reported as N. gottlandica) from Tasmania were also investigated. We here present a detailed morphological analysis of these diatoms, and compare it with the type material of N. gottlandica.
 Methods –Materials were analysed using Light and Scanning Electron Microscopy.
 Key results –The southern hemisphere populations represent two hitherto unknown taxa here described as Navicula bergstromiana and N. eileencoxiana. Important morphological differences include valve shape, stria density, shape of the central area, ultrastructure of the external central raphe endings, presence of a distinct internal accessory rib, and the relative width of the external longitudinal silica strips covering the valve face with respect to the longitudinal fissures separating these strips. While the new taxa show some affinity with the genus Haslea, the internal apical structure of the raphe, the external structure of the terminal raphe fissures and the central raphe endings (often with tooth-like protrusions, creating the impression of a satellite pore), and the apparent lack of the typical sandwich-type Haslea valve ultrastructure support the position of N. gottlandica and both new taxa within the genus Navicula.
 Conclusions – The description of two additional species with close similarities to N. gottlandica (i.e. possessing the typical longitudinal striae/silica strips and tooth-like protrusions in hooked central raphe endings) suggests that the N. gottlandica species group is more diverse than previously thought. The existence of closely similar Navicula species recently described from rivers in tropical South America but also from marine littoral samples in South and North America and China, raises intriguing questions about their phylogenetic relationships, ecology and biogeography.

Two fouling Olifantiella (Bacillariophyceae) species from the northwest temperate Pacific coast

Two naviculoid diatoms with an internal tubular process that opens externally through a pore or process on the valve face were observed on the hull of R/V Onnuri of the Korea Institute of Ocean Science & Technology in South Korea. Owing to the presence of distinctive morphological features, namely the buciniportula and an internal marginal canal, these diatoms were assigned to the genus Olifantiella, which was recently described from tropical regions. Of these two species, one (Olifantiella onnuria sp. nov.) is new to science. It can be distinguished from other Olifantiella species by two, internally closed, bean-like buciniportulae, and an external T-shaped groove near the terminal raphe endings. These morphological characteristics resemble those of the genus Labellicula, however, the presence of an internal marginal canal does not match Labellicula. The other Olifantiella species is identical to O. muscatinei, which possesses occluded fenestrulae on the valve face. The occurrences of these two Olifantiella species are the first records for the temperate Pacific region and their presence on a ship's hull indicates that Olifantiella spp. may be dispersed widely along shipping routes.

New Aulacoseira species (Bacillariophyta) from the Argentinean Patagonia and re-examination of type material of Melosira perpusilla Frenguelli

We present a detailed morphological analysis with light and scanning electron microscopy of two new small Aulacoseira species occurring in lacustrine sediments from small lakes in the provinces of Santa Cruz and Neuquén (Patagonia, Argentina). These species differ from similar taxa by unique combinations of characters. Aulacoseira lauquenensis sp. nov. can be differentiated by its broad collum, deep and solid ringleist and presence of short, spatulate and forked-tip spines. Aulacoseira liucoensis sp. nov. is distinguished by the presence of a marginal row of valve face areolae, straight mantle rows of coarse areolae, developed collum, protruding ringleist and conical, anchor-tip spines. Additionally, we re-examine the type material of Melosira perpusilla Frenguelli and present an analysis of its identity.

Study on optimization of laser cladding using Stellite 6 powder for exhaust valve face of marine engine

In this study, experiments with various parameters were performed to apply laser cladding to the exhaust valve face of a marine engine and optimum conditions were derived. The used specimen was an actual exhaust valve, and the heat source was a high-power diode laser. Cladding was applied to the exhaust valve face using the optimum conditions, and a sound clad layer without internal defects, such as pores and cracks, was formed. The average hardness of the clad layer formed under the optimum conditions was higher than 529 Hv. Component analysis showed a very low dilution rate inside the clad layer.

Extreme diversity in fine-grained morphology reveals fourteen new species of conopeate Nitzschia (Bacillariophyta: Bacillariales)

A study was made of the ultrastructural variation in a group of conopeate Nitzschia species, primarily marine species from Guam but also including one freshwater species from Costa Rica. Fourteen new species are described: Nitzschia alcyoneae, Nitzschia asteropeae, Nitzschia carahii, Nitzschia celaenoae, Nitzschia dagmannii, Nitzschia electrae, Nitzschia guamensis, Nitzschia jordanii, Nitzschia lascrucensis, Nitzschia maiae, Nitzschia meropeae, Nitzschia schefterae, Nitzschia spathulatoides, and Nitzschia taygeteae. The valves in all these taxa had a central raphe-sternum on a raised keel; from the keel arise silica flaps, the conopea, and the valve face was depressed below the conopea to form conopeal canals. The valve surface was thus differentiated into three regions, in which the areola pattern sometimes differed: the exposed valve face, the valve depression, and the peri-raphe zone, i.e., the exposed part of the keel wall between the conopeum and the raphe-sternum. We refer to this suite of characters as the tholophora (canopy-bearing) morphology. In one species, N. maiae sp. nov., the conopea occurred only at the apex and there was no valve depression. Thirty-eight morphological characters were used in addition to the usual morphometric data (length, width, densities of striae and fibulae); these included, inter alia, a remarkable range of areola shapes on the three valve regions and the copulae—oval/circular pores, transapical slits, longitudinal slits, small pores fields, continuous pores fields, and larger quadrate pores closed by hymenes or cribra; the extent of the conopea along the valve; the presence of longitudinal ribs on the valve, conopea, or copulae; and the extent of internal development of silica below the striae. Phylogenetic analysis of gene sequences from six species was entirely congruent with analysis of morphological characters.

Craticula widouensis, a new diatom (Bacillariophyta) species of a Sahelian temporary pond (North Senegal)

ABSTRACTDuring a floristic survey of temporal ponds in the Sahelian area of North Senegal, a new Craticula species (Bacillariophyceae) was discovered, and it is named here Craticula widouensis Beauger, C.E.Wetzel & Ector sp. nov. The new taxon is formally described using light and scanning electron microscopy. The species presents a unique set of morphological characteristics, including valve dimensions, outline, and presence of conspicuous elongated silica slats at the valve face/valve mantle junction and some narrow apically elongated struts irregularly distributed on the valve face, which make Craticula citrus (Krasske) E. Reichardt the most similar taxon to our knowledge. The ecological preferences of Craticula widouensis sp. nov. are eutrophic, contaminated, and hot ponds. A morphological comparison with the most similar species and a checklist of Craticula taxa are also presented.

웨이스트게이트 터보차저의 EWGA 링키지 시스템에 대한 열변형 거동 연구

The wastegate valve regulates the maximum boost pressure inside the turbocharger to prevent damage to the engine and turbocharger which can occur from overload. However, even though the opening and closing behaviors of the valve should be controlled accurately, thermal deformations of the turbocharger system can lead to excessive distortion of the actuator rod, which can have a significant effect on the turbocharger performance. In this study, thermal deformation analysis of the turbocharger assembly has been analyzed through finite element analysis under operation condition. The result shows that the deformation in the turbine housing is relatively large and actuator rod is bent by thermal load. It causes rotational deformation at the wastegate valve face connected to the rod. And it is efficient to increase the stiffness of the EWGA rod to minimize the rotational deformation of the valve face. It means that the actuator rod should be placed in a position close to the center of the turbocharger to minimize the length of the rod that has the greatest effect on stiffness enhancement.

Eunotia (Bacillariophyta) biodiversity from high altitude, freshwater habitats in the Mugecuo Scenic Area, Sichuan Province, China

Mugecuo Scenic Area is located in the northern Hengduan Mountains between the Sichuan Basin and the Qinghai-Tibet Plateau and has a subtropical humid monsoon climate. The area is at an altitude of 2600–3800 m above sea level (asl), with water originating mostly from melting mountain snow. In the region, a total of 20 Eunotia species have been identified, including two new species: E. mugecuo sp. nov., consisting of valves arched, clavate, ends broadly rounded, and terminal raphe fissures at the junction between valve face and mantle. The other newly-identified species is classified named as E. filiformis sp. nov., consisting of valves gently bent, ends not noticeably or only slightly inflated, broadly rounded, with external terminal raphe fissures curving in an angle of 180° back from apical nodules. Five newly recorded species have been identified in China, including E. odebrechtiana, E. michaelis, E. pomeranica, E. pseudogroenlandica and E. superpaludosa. Here, we discuss the new species and new taxon records through light and scanning microscopic documentation of valve morphology, along with key internal and external valve characteristics, and analyze the distribution of Eunotia in the Mugecuo Scenic Area.

Angusticopula rowlingiana, a new melosiroid diatom (Bacillariophyta) from Ascension Island (South Atlantic Ocean)

During a diatom survey of some samples from Ascension Island, a remote island located in the southern Atlantic Ocean, an unknown melosiroid diatom species was studied using both light and scanning electron microscopy. It proved to be a new species described as Angusticopula rowlingiana sp. nov. and characterized by a large number of narrow copulae in the girdle, a marginal ring of small granules, very small pores covering the entire valve face and occasionally having internal valves. The new species is compared with all Angusticopula species known worldwide and with several Melosira species showing a similar combination of characters. Short notes on its ecology are included.

New and interesting diatoms from Tibet: I. Description of a new species of Clipeoparvus Woodbridge et al.

We present light and scanning electron microscopical observations on frustules of a new species of Clipeoparvus Woodbridge et al. from Tibet. Cells are small, lens-shaped to conical, have internally occluded areolae and lack any processes. The Tibetan species differs from Clipeoparvus anatolicus Woodbridge, E.J. Cox & Roberts, the only other known species of the genus described from Turkey, by the number, size and structure of the spines on the valve face. Two morphs were encountered, one bearing spines and the other without spines, and they can occur separately or in the same frustule. This phenomenon may be an example of Janus cells within this taxon. The biogeographic distribution of this taxon is discussed.

Morphological variability in Alveolophora areolata (Moisseeva) Moisseeva and Alveolophora bifaria Nevretdinova & Moisseeva

The morphological variability of two biostratigraphically important diatom species of the Russian Far East, Alveolophora areolata (Moisseeva) Moisseeva and Alveolophora bifaria Nevretdinova et Moisseeva,was studied using light and scanning electron microscopy. High variability was found in mantle height, diameter, stria organization, areola location on the valve face, alveolus structure and costae of A. bifaria, but less variability in A. areolata. Separation valves of A. areolata lack spines, and rimoportulae were found on the valve face for the first time. Based on the new morphological data, descriptions for these taxa have been emended.

Performance of different abrasive tools in electrochemical honing of coated surfaces

This paper highlights on the honing characteristics of various abrasive tool materials during the precision finishing of EN52 coated surface of the engine valve face using electrochemical honing ECH process. The investigation on various abrasive tool materials in ECH is first proposed, and it may help to enhance the processing of sophistic surfaces. It is a new technique, which in spite of being used in some industrial plants, in particular to smooth surfaces and is still not fully described due to the variety of the factors affecting the process. More information about the process is required, especially the honing related parameters, such as abrasive tool pressure, abrasive material, and abrasive size. Special shaped honing tools were designed and fabricated to study the present aspects. Two different types of abrasive tool material (Al2O3 and NiCr) for honing operation were used while ECH of EN52 work surface. The results of the experiments are finally furnished with the aim to generalise a useful guideline for the user to enable proper selection of conditions for obtaining good surface quality.

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.

Diversity in the section Compressa of the genus Chaetoceros (Bacillariophyceae), with description of two new species from Chinese warm waters.

Monoclonal strains of Chaetoceros species were collected from Chinese warm waters. Vegetative cells and resting spores were examined using light microscopy as well as scanning and transmission electron microscopy. Combined morphological and DNA sequence data from the hypervariable D1-D3 region of the nuclear ribosomal large subunit showed the presence of two new species within the section Compressa, herein described as Chaetoceros bifurcatus sp. nov. and C.millipedarius sp. nov. Both species possessed features typical of the section Compressa, but C.bifurcatus was characterized by the heavy intercalary setae fusing and extending together for a distance before diverging. The heavy setae were not visually contorted, lacking poroids and spines, in contrast with how the section Compressa has been defined. Chaetoceros millipedarius was characterized by a horizontal stagger of ordinary intercalary setae when the chain was seen in broad girdle view, making the chain look like a millipede. The two new species were supported by molecular phylogenetic analyses with C.bifurcatus sister to C.contortus var. ornatus, while C.millipedarius was sister to C.contortus var. contortus. Based on the morphological features exhibited in C.bifurcatus, the diagnosis of the section Compressa was emended to exclude "contorted" heavy setae and compressed valve faces.

A new species of Genkalia (Bacillariophyta) from mountain lakes within the Sichuan Province of China

A new diatom species, Genkalia alpina sp. nov., was identified in high elevation lakes in the Mugecuo Scenic Area within the Sichuan Province of China. The area is located in the northern foot of the Hengduan Mountains between the western edge of the Sichuan Basin and the Qinghai-Tibet Plateau, belongs to the subtropical humid monsoon climate, at an altitude of 2600–3800m, with lake water originating mostly from the melting mountain snow. Light and scanning electron microscopy revealed that G. alpina valves are linear with two undulated margins and apices that are subcapitate in larger specimens, but slightly shorter in smaller specimens. The central area is elliptical, and the external proximal raphe ends are straight, or slightly deflected towards the primary valve side. Terminal raphe fissures are strongly bent towards the secondary side and they extend to mantle. Uniseriate striae continue uninterrupted from the valve face to the mantle. The present study is the first report of Genkalia species in China, and expands the geographical distribution of the genus, as well as the known diatom diversity of China.