Valve Ultrastructure Research Articles

A new species of Germainiella (Bacillariophyta) from the Myristica swamps of the Western Ghats, India

Germainiella chandranii sp. nov. is described from a Myristica swamp of the Western Ghats, India, on the basis of light and scanning electron microscopy. The new species resembles two related genera, Fallacia Stickle & D.G. Mann and Germainiella Lange–Bertalot & Metzeltin on the basis of valve morphology, but a thorough investigation of valve ultrastructure confirms its placement in Germainiella. External valve outline and morphology, large conopeum covering the entire face of the valve, siliceous struts running perpendicular to the raphe support the generic assignment. The main diagnostic features of the new species are the presence of small tubules running perpendicular to the raphe, striae composed of a series of round to elongated areolae, which are not covered internally by hymenes, and a larger central area. The new species occurs in acidic waters of the Myristica swamps of the Western Ghats and it can be considered as an indicator of the acidic condition.

First Report and New Freshwater Species of Germainiella (Bacillariophyta) from the Maolan Nature Reserve, Guizhou Province, China

We present light and scanning electron microscopic observations on the valve ultrastructure of 4 species of the genus Germainiella from the Maolan Nature Reserve from Guizhou Province, China. This is the first report of the genus from China. The new species differ in the shape and size of the valves, but they all have the large conopeum covering the entire face of the valve. One species, G. sinica, lacks small tubules running perpendicular to the raphe opening, one of the defining features of the genus, and in having the large conopeum but lacking the tubules resembles another diatom, Fallacia emmae, described from the subantarctic region. We conclude that Germainiella and Fallacia, as typified by F. pygmaea, are not closely related, but species assigned to Fallacia may be closely related to Germainiella. A new combination, G. emmae, is proposed. We discuss the nature of conopea, and other small, finely-structured naviculoid diatoms that might be better placed in Germainiella. The genus is now recognized to have a total of 7 species, 4 of which are from the Maolan Nature Reserve.

A new sediment dwelling and epizoic species of Olifantiella (Bacillariophyceae), with an account on the genus ultrastructure based on Focused Ion Beam nanocuts

The marine diatom Olifantiella Riaux-Gobin et Compere predominantly occurs in tropical Indo-Pacific coral reef environments. The genus has about a dozen validly published taxa and is characterized by transapically elongate striae composed of a macroareola, broad perforated girdle, and tubular buciniportula process of trumpet-shape. The valve mantle of taxa related to the generitype, O. mascarenica, have a canal-shaped structure around the valve at the face / mantle junction, while those to O. gorandiana have a simple mantle or strongly narrow canal and complex buciniportula composed of hollow processes. The geographic distribution of Olifantiella is expanded in this study to include species observed in loggerhead sea turtles scrapes from the Aegean Turkish coast and samples from the Turkish Black Sea and Adriatic Sea coasts. Olifantiella has also been identified in Martinique Island, Caribbean Sea. A transfer of Navicula infirmitata is proposed due to the areola and buciniportula structure, as Olifantiella infirmitata. Further, an application of the Focused Ion Beam (FIB) to a sequential cutting of frustules allows resolution of Olifantiella mascarenica valve ultrastructure.

Cocconeis cascadensis, a new monoraphid diatom from mountain streams in Northern California, USA

A new diatom species, Cocconeis cascadensis, is reported from streams in the Southern Cascade Mountain Range in California (USA). Light and scanning electron microscopy reveals morphological novelties related to the structure of the areolae on the sternum valve, which are surrounded externally by crater-like depressions, as well as apically elongated bumps in the submarginal hyaline area of the raphe valve. The valve morphology of the coarsely striated taxa, Cocconeis placentula var. lineata, C. pseudolineata and C. neodiminuta from the studied streams, and C. disculus from freshwaters in Europe, is presented for comparison. The newly described species possesses a unique combination of morphological features, representing an intermediary between the more complex valve ultrastructure of marine Cocconeis taxa and the freshwater members of the C. placentula species complex, with simple slit-like areolae. Cocconeis cascadensis inhabits cold-water mountain streams with low conductivity, low nutrients and low dissolved organic carbon concentrations.

Sellaphora gologonica sp. nov. (Bacillariophyta, Sellaphoraceae), a new diatom species from a Mediterranean karst spring (Sardinia, Italy)

A new epilithic Sellaphora (Bacillariophyceae) species from a karst spring of Sardinia is described based on light and scanning electron microscopic observations. Sellaphora gologonica sp. nov. shares similarities with small-celled Sellaphora previously described from Europe and particularly with S. atomoides, S. hafnearae and S. seminulum. Sellaphora gologonica seems to be related to S. seminulum based on the striae patterns and valve ultrastructure, as well as the sinuous raphe system. The main differences between S. gologonica and S. seminulum lies in its valve shape (small, elliptic to oval), not presenting capitated nor protracted apices, as in the later taxon. Sellaphora gologonica was discovered in freshwater habitats with slightly alkaline and oligotrophic waters presenting medium hardness and mineralization, at the smaller water emergence of karst spring system Su Gologone (Sardinia).

Cocconeis neuquina Frenguelli (Bacillariophyta): emended description, lectotypification, ecology, and geographical distribution

In this article, we examine the type material of Cocconeis neuquina Frenguelli from the type locality in Neuquén province and other samples in southern Santa Cruz province (Patagonia, Argentina). Cocconeis neuquina is a small species with an oval-subcircular to broadly elliptical valve outline. The sternum valve is externally convex, striae are radiate and uniseriate, and areolae are rounded towards the mantle. The raphe valve is externally concave, the raphe is straight and filiform, striae are uniseriate, slightly radiate, and the first areola close to the mantle is drop-shaped. With this contribution we aim to clarify the morphology of this species, provide a more detailed description of valve ultrastructure, present its lectotypification and extend its geographical distribution.

Gomphonemopsis ligowskii, a new diatom (Bacillariophyceae) from the marine Antarctic and a comparison to other Gomphonemopsis

A new marine diatom, Gomphonemopsis ligowskii, is described. Gomphonemopsis ligowskii was found as an epiphyte on the brown macrophyte, Desmarestia anceps, collected from King George Island, Antarctica in January 2016. This species is the first of the genus described from a polar region. It is a small and relatively rare taxon that is characterized by its unique shape and the presence of uniseriate striae, composed of round poroidal areolae on its valve face. The striae are arranged in parallel rows on either side of the axial area, and a row of rounded areolae on both sides of the valve mantle is confined to the wider part of the valve (headpole). A description of valve ultrastructure as well as a comparison with related taxa are provided.

The distribution and coordination of trace elements in Krithe ostracods and their implications for paleothermometry

The Mg and Sr content of ostracod valves have been used to reconstruct past temperature and salinity, and their stable isotopes have been used to reveal aspects of marine, lake and estuary hydrology. However, significant uncertainties surround ostracod calcification processes, the incorporation mechanisms of trace elements, and the sensitivity of proxy tracers to complex confounding factors. The valves of most ostracods are composed of micron-scale crystalline grains embedded in an organic matrix. The fine-scale geochemistry of these structures, and the nature of the influence of biological mineralisation processes on valve chemistry, remain poorly constrained. We have performed sub-micron resolution X-ray microscopy of a marine Krithe ostracod valve, and determined the chemical coordination of Mg, and the distribution of Mg, Na and S throughout the crystal-organic valve structure. These trace elements display systematic sub-micron-scale compositional variations within the mineral grains and inter-granular matrix of the valve ultrastructure. These patterns imply that Krithe biomineralisation processes significantly modulate trace element incorporation at the sub-micron scale. Thus Krithe chemical composition is likely to be decoupled to some extent from the water in which they calcified. Most importantly, Mg K-edge Near-Edge X-Ray Absorption Fine Structure (NEXAFS) spectra, and the coincidence of high-Mg regions with S-rich organic layers reveal that Mg is not primarily hosted in the calcite structure in the valve. Our results highlight the need to understand the processes that drive this fine-scale chemical heterogeneity and their influence on connections between the external environment and valve geochemistry, if ostracods are to be used as sources of paleoenvironmental proxies.

Detergent-based decellularization strategy preserves macro- and microstructure of heart valves.

Biological tissue has great potential to function as bioprostheses in patients for heart valve replacement. As these matrices are mainly xenogenic, the immunogenicity needs to be reduced by decellularization steps. Reseeding of bioscaffolds has tremendous potential to prevent calcification upon implantation, so intact microstructure of the material is mandatory. An optimal decellularization protocol of heart valves resulting in adequate preservation of the extracellular architecture has still not been developed. Biological scaffolds must be decellularized to remove the antigenic potential while preserving the complex mixture of structural and functional proteins that constitute the extracellular matrix. Here, we compared 3 different decellularization strategies for their efficiency to remove cells completely while preserving the porcine heart valve ultrastructure. Porcine pulmonary heart valves were treated either with trypsin-ethylenediaminetetraacetic acid (TRP), a protocol using detergents in combination with nucleases (DET + ENZ), or with Accutase® solution followed by nuclease treatment (ACC + ENZ). The treated heart valves then were subjected to histological, DNA and scanning electron microscopic analyses. All DNA fragments were removed after ACC + ENZ treatment, whereas cellular removal was incomplete in the TRP group. TRP and ACC + ENZ-treated valves were enlarged and showed a disrupted architecture and degraded ultrastructure. In contrast, fully acellular heart valves with intact architecture, layer composition and surface topography were achieved with DET + ENZ treatment. DET + ENZ treatment yielded excellent results in terms of preservation of material architecture and removal of DNA content. Compared to TRP and ACC + ENZ procedures, DET + ENZ-treated porcine pulmonary heart valves demonstrated well-preserved macroscopic structures and microscopic matrix components and represent an excellent scaffold for further application in tissue engineering.

The planktonic diatom genus Chaetoceros Ehrenberg (Bacillariophyta) from the Adriatic Sea

The morphology of the genus Chaetoceros, one of the most abundant and diverse planktonic diatom groups, was investigated using material collected in the eastern Adriatic Sea from 2006 to 2012. Twenty-seven morphologically distinct species have been identified from both field samples and cultivated strains. Two species, C. bacteriastroides and C. pseudodichaeta, are reported for the first time for the area. Morphometric data, general morphology and ultrastructural characters are presented for each species, based on light and electron microscopy observations, with a special emphasis on species-specific distinctive features. Valve ultrastructure appeared to be characteristic for single species or group of closely related species, especially inside the subgenus Hyalochaete. A collection of appropriate micrographs will facilitate future identification of Chaetoceros species and morphological comparison with material from other geographic areas.

Two new species in the Chaetoceros socialis complex (Bacillariophyta): C.sporotruncatus and C.dichatoensis, and characterization of its relatives, C.radicans and C.cinctus.

The diatom genus Chaetoceros is one of the most abundant and diverse phytoplankton in marine and brackish waters worldwide. Within this genus, Chaetoceros socialis has been cited as one of the most common species. However, recent studies from different geographic areas have shown the presence of pseudo-cryptic diversity within the C.socialis complex. Members of this complex are characterized by curved chains (primary colonies) aggregating into globular clusters, where one of the four setae of each cell curves toward the center of the cluster and the other three orient outwards. New light and electron microscopy observations as well as molecular data on marine planktonic diatoms from the coastal waters off Chile revealed the presence of two new species, Chaetoceros sporotruncatus sp. nov. and C.dichatoensis. sp. nov. belonging to the C.socialis complex. The two newspecies are similar to other members of the complex (i.e., C.socialis and C.gelidus) in theprimary and secondary structure of the colony, the orientation pattern of the setae, and the valve ultrastructure. The only morphological characters that can be used to differentiate the species of this complex are aspects related to resting spore morphology. The two newly described species are closely related to each other and form a sister clade to C.gelidus in molecular phylogenies. We also provide a phylogenetic status along with the morphological characterization of C.radicans and C.cintus, which are genetically related to the C.socialis complex.

Williamsella iraqiensis sp. nov., a new diatom (Bacillariophyta, Fragilariophyceae) from Sawa Lake, South Iraq

A new species of the genus Williamsella (Fragilariophyceae) is described from a saline lake in southern Iraq. Williamsella iraqiensis sp. nov. was found free living and as epiphyte on Chara sp. in Sawa Lake. This species is the second described of the genus Williamsella which was originally reported from Blue Lake warm springs, Utah, USA. Williamsella iraqiensis sp. nov. and W. angusta can be readily distinguished under LM by having a relatively wide sternum which results from shorter striae along valve margin. Description of valve ultrastructure and comparison with other related genera such as Fragilaria is provided. Williamsella iraqiensis is a brackish water species preferring warm waters.

Typification, valve ultrastructure, and systematic position of Gomphonema gomphopleuroides Amossé ex Kociolek, Glushchenko and Kulikovskiy, an endemic diatom from Southeast Asia

Light and scanning electron microscope observations are presented on the diatom Gomphonema gomphopleuroides. This astigmate species, described originally from Vietnam, is large and robust, and has raphe branches that are shorter than in most other freshwater gomphonemoid diatoms. The uniseriate striae are unoccluded and the areolae are bordered by lunate ridges on one side, another unique feature of the species. Internally there is an apically elongated central nodule. This species is contrasted with the genus Gomphopleura, which also has shortened raphe branches. Gomphonema gomphopleuroides appears morphologically most similar to G. kaznakowi, a species endemic to southern China. The name G. gomphopleuroides is validated here with the designation of a neotype.

Licmosphenia revisited: transfer to Licmophora, redescription of L. clevei Mereschkowsky and descriptions of three new species

Licmosphenia Mereschkowsky (Licmophorales: Licmophoraceae) is distinguished from Licmophora C. Agardh almost entirely by the presence of an apical window in the septum of the valvocopula. Recently, SEM images of three new species, all with coarse striae, showed that the valve morphology was indistinguishable from a group of Licmophora species including L. ehrenbergii, and gene sequence data showed Licmosphenia sister to the few available Licmophora spp. Two questions remain: (1) what is the structure of Licmosphenia spp. with fine striae? and (2) what would further molecular evidence contribute to understanding whether these genera are distinct or not? New LM and SEM observations on Licmosphenia species and sequence data from additional Licmophora species now answer these questions. Valve ultrastructure of a new, finely striated species with a small apical aperture, from Mallorca, Spain, is similar to finely striated Licmophora species, and the position of Licmosphenia in the phylogenetic tree is now within the Licmophora clade. The presence of apical apertures in two morphological groups of Licmophora suggests that the apical window has arisen at least twice. Licmophora is the older genus name and we therefore formally transfer all Licmosphenia species to it. In addition to Licmophora garyi from Mallorca, we describe a curved species from the Adriatic, Licmophora arcuata, similar to L. grunowii but with much coarser striae, and a species from Guam with a very large apical aperture, L. pisciformis. We also designate an epitype for Licmosphenia clevei Mereschkowsky, the type species of that genus.

Two new Prestauroneis Bruder & Medlin (Bacillariophyceae) species from Zoigê Wetland, Sichuan Province, China, and comparison with Parlibellus E.J. Cox.

We present light and scanning electron microscopy on two new species of Prestauroneis from the Zoigê Wetland, Sichuan Province, China. Prestauroneis nenwai sp. nov. is rhomboid in shape with acutely rounded apices. Striae around the central area are more widely spaced than elsewhere on the valve, and distinct pseudosepta are present. This new species is distinguished from the two previously described species in this genus by the shape and size of the valves. Prestauroneis lowei sp. nov. is more elliptical in outline, with barely protracted, broadly rounded apices. An indistinct pseudoseptum is present at each pole. This second new species is similar to Parlibellus protracta, but differs in outline, especially in the degree to which the headpole is protracted. Some species similar to Prestauroneis have been included in Parlibellus, a genus of quite different morphology. We compare the differences between these two genera, and based on published observations of valve ultrastructure we propose two new combinations, Prestauroneis protractoides (Hustedt) Q. Liu & Kociolek comb. nov. and Prestauroneis protracta (Grunow ex Cleve) Q. Liu & Kociolek comb. nov. Assignment to Prestauroneis of other species in Parlibellus awaits future scanning electron microscopy studies. Although currently a small genus, Prestauroneis may be found across a wide spectrum of environments, from fresh to brackish/marine waters.

Ultrastructure of internal jugular vein defective valves.

ObjectivesTo study the ultrastructure of intraluminal defects found in the internal jugular vein by using a scanning electron microscopy.MethodsUsing a scanning electron microscopy, intraluminal septa and/or defective valves blocking the flow in the distal internal jugular vein of seven patients were studied together with the adjacent wall and compared with control specimen.ResultsThe internal jugular veins’ wall showed a significant derangement of the endothelial layer as compared to controls. Surprisingly, no endothelial cells were found in the defective cusps, and the surface of the structure is covered by a fibro-reticular lamina.ConclusionsAlthough the lack of endothelial cells in the internal jugular vein intraluminal obstacles is a further abnormality found in course of chronic cerebrospinal venous insufficiency, our investigation cannot clarify whether this finding is primary or caused by progressive loss of endothelium in relation to altered haemodynamic forces and/or to a past post-thrombotic/inflammatory remodelling.

Valve disease in chronic venous disorders: a quantitative ultrastructural analysis by transmission electron microscopy and stereology

The ultrastructure of venous valves and walls in chronic venous disease was investigated. Consecutive patients were categorised into one of three groups (group A: patients with C1 venous disease in accordance with CEAP (Clinical severity, Etiology, Anatomy, Pathophysiology); group B: C2 and C3; group C: C4, C5 and C6). The terminal or preterminal valve and adjacent vessel wall was harvested from the great saphenous vein. Sections were examined with a transmission electron microscope. The volumes of elastin and of collagen per unit surface area of valve were assessed, as well as the surface endothelium of valve and vessel wall. The study population consisted of 17 patients. The elastin ratio was analysed by means of stereology. Mean values were: in group A, 0.45 μm3/m2; in group B, 0.67 μm3/m2; in group C, 0.97 μm3/m2. The ratio was similar for collagen (A, 15.7 μm3/m2; B, 26.8 μm3/m2; C, 30.1 μm3/m2). Surface analysis of the valve endothelium and the adjacent vessel wall endothelium showed a trend towards increasing damage with more severe disease. With progression of venous disease, the valve elastin content, assessed morphologically, seems to increase, and the endothelium of the venous valve and the vein wall tend to show more damage.

Alveolophora robusta comb. nov. from Miocene deposits of the Vitim Plateau, Russia

The valve ultrastructure of the paramount biostratigraphic indicator species, Aulacoseira robusta Khursevich, was studied from Miocene freshwater sediments of the Vitim Plateau under light and scanning electron microscopy. Comparison between freshwater taxa of Aulacoseira Thwaites and Alveolophora Moisseeva & Nevretdinova supports the transfer of A. robusta to the genus Alveolophora. Diagnostic features of this species include robust internal pervalvar costae separating the alveolae, deep ringleiste with multiple rimoportulae and a submarginal ring of siliceous markings (short radial ridges) on the valve face.

MORPHOLOGICAL STUDIES OF SOME MARINE MASTOGLOIA (BACILLARIOPHYCEAE) BELONGING TO SECTION SULCATAE, INCLUDING THE DESCRIPTION OF NEW SPECIES.

Epiphytic diatoms on seagrass and seaweed were collected from tropical (e.g., Siladen Island, Celebes Sea, Indonesia and Phú Bài, China Sea, Vietnam), subtropical (e.g., Sharm el-Sheikh, Red Sea, Egypt), and temperate regions (e.g., Patmos Island, Greece) in 2000, 2005, and 2006. Eight species of Mastogloia, belonging to the section Sulcatae, are described mainly through scanning electron microscopy, including two new species to science, M. oculoides and M. sergiana. These species show a differently shaped median depression on the external valve face between the raphe-sternum and the valve margin. Moreover, they lack a developed conopeum or pseudoconopeum, which covers the median depression in other species of the section Sulcatae. This study gives new insights on the ultrastructure of the Mastogloia's valves and provides an update of their current geographical distribution.

Decellularization of Heart Valve Matrices: Search for the Ideal Balance

Currently used decellularization procedures have negative effects on extracellular matrix (ECM) integrity. The objective of this study is to evaluate four decellularization methods and their effect on the collagen ultrastructure, mechanical behavior and antigenicity of porcine aortic valves. Aortic valves were placed in a trypsin, osmotic, trypsin-osmotic or detergent-osmotic solution. Leaflets were processed for histology and mechanical testing. Matrices were implanted subdermally in rats to evaluate immune reaction and calcification. Trypsin-osmotic methodology effected near-complete decellularization. Trypsin treatment resulted in cell removal only in the spongiosa layer. Osmotic and detergent-osmotic treatments did not remove any cells from the cusps. Mechanical strength was significantly inferior in the trypsin (p50,03) and trypsin-osmotic treated group (p50,04). Trypsin and trypsin-osmotic decellularized matrices evoked a strong CD31 inflammatory cell infiltration. Enzymatic-osmotic decellularization appears to be the only effective method to remove cellular components. However, the near cell free scaffolds still evokes a strong CD31 T-cell inflammatory reaction.