Valve Face Research Articles

AULACOSEIRA PUSILLA (BACILLARIOPHYTA) – НОВЫЙ ВИД ДЛЯ ФЛОРЫ ВОЛЖСКИХ ВОДОХРАНИЛИЩ

In this paper, we restudy the morphology of A.subarctica low-frustule forms from the Volga reservoirs (Ivankovo, Gorky and Kuibyshev) using scanning electron microscopy. These forms occur as short colonies and one of them, by quantitative (colony size, valve diameter and mantle height, valve height/diameter ratio, number of areola rows and areolae in 10 µm) and qualitative (shape of spines, areolae arrangement of valve face and mantle) characteristics, corresponds to A.pusilla. The latter is a cosmopolitan species, new for the flora of Volga. A. Pusilla is very similar to A.subarctica by morphology and these two species are often found together that may cause problems with their identification.

Encyonopsis indonesica sp. nov. (Bacillariophyceae, Cymbellales), a new diatom from the ancient lake Matano (Sulawesi, Indonesia).

A new species, Encyonopsis indonesica, is described from the ancient lake Matano, Sulawesi island, Indonesia. The morphology of this species was studied by means of light and scanning electron microscopy. E. indonesica has a remarkable valve ultrastructure. The valve surface is ornamented with numerous longitudinal siliceous ribs and siliceous verrucae. Valve face delineated from the mantle by a thickened marginal ridge. Raised sterna border the raphe branches. Raphe is distinctly undulate with distal ends hooked strongly to the ventral side. The only similar species to E. indonesica is Amphora dissimilis described from New Caledonia. Comparison of both taxa is given and A. dissimilis is transferred to Encyonopsis. The taxonomic placement of both taxa is evaluated, and the phenomenon of external siliceous ornamentation is discussed.

Luticola rojkoviensis sp. nov. (Bacillariophyta), a new terrestrial diatom from Central Slovakia

Sampling of fungi in a grassland on a hill in Rojkov, Central Slovakia, revealed a new species of Luticola (Diadesmidaceae). Its terrestrial populations were found close to the basis of the fertile part of the geoglossoid fungi (Geoglossaceae) that were overgrown with filamentous cyanobacteria of the orders Oscillatoriales and Synechococcales. Luticola rojkoviensis sp. nov. is characterized by the valve outline and the structure of the external valve face: valves are weakly dorsiventrally asymmetrical, rhombic-lanceolate in larger cells to rhombic-elliptic and tri-undulate in smaller cells, with shortly protracted and broadly rounded valve apices. Valve face is minimally concave, as the axial area is lowered and the area around distal raphe elevated. The surface of the valve is mostly uneven due to many depressions, so the external shape of the areolae and the impression of irregular longitudinal rows depend on the extent of these valve ornamentations. Proximal raphe endings are unilaterally slightly deflected, expanded into small central pores. The shape of both the proximal and the distal raphe fissures is slightly asymmetrical. The morphological characteristics of Luticola rojkoviensis sp. nov. are remarkably similar to those of L. hustedtii Levkov, Metzeltin et A.Pavlov, L. ectorii Levkov, Metzeltin et A.Pavlov and L. acidoclinata Lange-Bertalot. The association of Luticola rojkoviensis sp. nov. with geoglossoid fungi and epiphytic cyanobacteria is discussed.

Морфологія, таксономія та поширення рідкісного виду Aulacoseira cataractarum (Hustedt) Simonsen (Bacillariophyta) в Росії

This scanning electron microscopy study was undertaken to reanalyze frustule samples of the centric diatom algae Aulacoseira cataractarum, collected earlier from a swamp in the Uzon volcanic caldera (Kamchatka). This species, under the name of Melosira cataractarum, was reported before from a number of waterbodies in Russia. Later it was transferred to the genus Aulacoseira Thwaites – A. cataractarum (Hustedt) Simonsen (Simonsen, 1979), and then – to the genus Pseudostaurosira (A.Grunow) D.M.Williams & F.E.Round, under the name of P. seudostaurosira cataractarum (Hustedt) Wetzel, Morales et Ector. In this study we specify perforation of intercalary bands, the shape of the valves and spines as well as the number of valve face and mantle areolae per stria and their shape. Based on the original and published data an extended diagnosis of P. cataractarum is presented. Scanning electron microscope images of frustules of the centric diatom algae.

<strong><em>Staurosirella paranaensis sp. nov.</em>, a new epiphytic freshwater diatom (Bacillariophyceae) from the Paraná River floodplain, Brazil, South America</strong>

A new diatom species, Staurosirella paranaensis, is described only from epiphytic samples on the macrophyte Eichhornia azurea in a lake from the Upper Paraná River Floodplain in Brazil. Description of the new taxon is based on morphological characteristics observed using light and scanning electron microscopy. The new species is characterized by short elliptic valves with an axial area narrowly lanceolate, sometimes giving the impression of having a zig-zag form due the alternating nature of the striae. The lineolate striae, running uninterrupted from valve face to mantle. Spines are solid, thin, spatulate with two prominences at the top, located at the costae. Apical pore fields are inconspicuous, located at both apices and equally developed on both valves. Girdle elements variable in number, open, lacking pores, ligulated, and with valvocopula being much larger. The species previously identified in the region as the “catch-all” taxon “Staurosirella (Staurosira) pinnata” is placed in the genus Staurosirella based on the striae bearing well-developed internal vimines delimiting typically long areolae. Comparisons with similar species ascribed to the genus Staurosirella are provided to highlight the peculiar characteristics of S. paranaensis.

<p><strong>Three new needle-shaped <em>Fragilaria</em> species from Central America and the Tibetan Plateau</strong></p>

Three new needle-shaped Fragilaria species from freshwater lake Apastepeque in El Salvador (Fragilaria salvadoriana sp. nov., F. maarensis sp. nov.) and subsaline lake Nam Co on the Tibetan Plateau (F. huebeneri sp. nov.) are described and compared based on light and scanning electron microscopy observations and morphometric analyses. Fragilaria salvadoriana sp. nov. is characterized by narrowly linear-lanceolate, sometimes centrally constricted valves, subcapitate to rarely capitate apices, and a distinct, dented appearing central area. Striae are composed of 2−5 occluded areolae. It can be differentiated from similar needle-shaped species by the valve outline, relatively low striae density, and shark fin-shaped spines. Characteristic of F. maarensis sp. nov. are a very narrowly lanceolate valve outline and subcapitate apices. The apical pore field is composed of 2–3 rows of poroids and acute, irregularly oriented spines are present at the junction between valve face and mantle. This taxon is clearly different from other Fragilaria species, displaying a high length-to-width ratio and a low number of areolae per stria. The Tibetan species, F. huebeneri sp. nov., forms long ribbon-like colonies linked together by spatula-shaped spines. Valves have subcapitate apices, a spindle- to needle-shaped outline and an indistinct central area. Striae are alternate and composed of 3–5 areolae per stria. Teratological forms of F. huebeneri sp. nov. were commonly observed in the sediment trap samples. Fragilaria salvadoriana sp. nov. and F. maarensis sp. nov. were found in a warm, tropical crater lake characterized by low conductivity and dissolved oxygen content, medium alkaline pH, and magnesium-calcium-bicarbonate-rich waters. Fragilaria huebeneri sp. nov. was frequent in a large, high elevation lake with increased specific conductivity, alkaline pH and sodium-bicarbonate-rich waters. The new species are compared to morphologically similar species from the genus Fragilaria Lyngbye and ecological preferences are discussed.

Levels without Bosses? Entrepreneurship and Valve’s Organizational Design

Valve is a “flat” company without a management hierarchy or traditional boss roles: instead of top-down organization and management, Valve employees are free to work on whatever projects they choose and to convince other employees to join collaborative groups. Decision-making is thus “democratized” rather than centralized in key management positions. This peculiar structure, or lack thereof, seems to challenge conventional ideas about organization not only in the video game business but also business in general. We say “seems to” because, as we will explain, the company’s story is more complicated than either its supporters or critics tend to acknowledge. In this chapter, we explore Valve’s economic organization and discuss the challenges it faces. We thereby provide a clearer and more comprehensive story of this organization, while also providing a foundation for future research on the gaming industry as well as on economic organization more generally. In particular, we use our survey of Valve’s unique organization to draw implications for theories of entrepreneurship, projects, strategy formation, and organizational capabilities. To do this, we draw on a range of publicly available data and first-hand accounts of the company, as well as available secondary literature. We also use the case of Half-Life 3, a highly-demanded-yet-never-made game, and Half-Life: Alyx, as examples of challenges organizations such as Valve face.

Integrative taxonomic description of two new species of the Cocconeis placentula group (Bacillariophyceae) from Korea based on unialgal strains

Cocconeis coreana and C. sijunghoensis are described as new based on micromorphological and molecular data. C. coreana is represented by five unialgal cultures from four different freshwater bodies, two from North Korea and three from South Korea. C. sijunghoensis is represented by two unialgal cultures from a brackish water body in North Korea. Except for one, all of the strains auxosporulated and showed an almost quadrupling of size in length and width. Morphologically, these species with their two different elliptical valves belong to the Cocconeis placentula group. The raphe valve has striae with uniseriate areolae continuing across a pronounced submarginal hyaline rim to the edge of the valve. The sternum valve has uniseriate dash-like areolae continuously from the valve face until the valve edge. Micromorphologically, these species possess two different open valvocopulae: only the raphe valvocopula has fimbriae; the sternum valvocopula has none. Based on p-distances of currently available DNA sequence data, i.e., rbcL and 18SV4, both species are pronouncedly different from the epitype strain of C. placentula, with C. coreana closest to the published molecular data of the strain UTEX FD23 named C. placentula from Iowa, USA, while C. sijunghoensis is closest but not the same as the published molecular data of strain D36_012, the epitype strain of C. placentula from Berlin, Germany. Based on scanning electron microscope observations, differentiating features are discussed concerning valvocopula fimbriae, central area, areolation of the sternum valve and on the raphe valve especially between the submarginal hyaline rim and edge. Key words: auxospores; cultures; micromorphology; molecular markers; morphometrics; 18SV4 & rbcL

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.

<p><strong><em>Scoliolyra</em> <em>elliptica</em> gen. et sp. nov. (Bacillariophyceae), a new marine genus from sandy beach in Southern China</strong></p>

Observation of sand samples collected from an estuarine sandy beach in Southern China revealed the presence of a new biraphid diatom. It is characterized by the presence of a twisted raphe system, apically elongate areolae, and striae interrupted by longitudinal H-shaped lateral areas in a form of valve face depressions, as well as girdle composed of open, plain copulae. The structure of valve outline, the raphe sternum and striae bears some resemblance to some established genera including e.g., Lyrella, Fallacia, Scolioneis, Scoliopleura and Scoliotropis, however, these characters are uniquely combined in this novel taxon. The new species, Scoliolyra elliptica, belongs to a new biraphid genus, Scoliolyra, and it is tentatively placed within the family Scolioneidaceae.

<p><strong>Taxonomy, valve ultrastructure, nomenclature and a comparison of two species of Bacillariales from freshwaters of Puerto Rico</strong></p>

We have investigated two canal-raphe bearing taxa from two freshwater long-term ecological monitoring sites in the NEON program from Puerto Rico. The identity of these two taxa have been misunderstood, and they have been mistaken for one another, due to being similar in size, shape and having interrupted striae across the valve face. Denticula occidentalis Østrup was described from the U.S. Virgin Islands, and like its congeners has fibulae that extend across the valve face as thickened ribs. The species also has valvocopulae that are typical for the genus, with arched sections that clasp onto the knob-like fibulae. Denticula occidentalis has a discontinuous raphe system, and external proximal raphe ends are hooked towards the valve center and elongated. Grunowia portoricensis, sp. nov. has fibulae restricted to the raphe side of the valve, though unlike most members of the genus the fibulae are knob-like. The raphe is continuous across the central area. Though described here as new to science, the species has been illustrated previously from Venezuela. Distinctions between Nitzschia, Denticula and Grunowia are discussed.

A new diatom (Bacillariophyceae) species from a thermal spring in Azores archipelago (São Miguel island, Atlantic Ocean)

Background: Due to their isolation, islands offer excellent areas for the study of distribution of benthic diatoms. On the other hand, diatoms bearing canal raphe have received less attention compared to other groups of diatoms such as Navicula, Pinnularia or Amphora .
 Questions: Is it possible that thermal springs on islands offer a refuge for infrequent diatom species?
 Studied species: Platichthys furnensis C. Delgado, V. Gonçalves & S.F.P. Almeida sp. nov.
 Study site and dates: The species here described was collected in the epilithon of a thermal spring in São Miguel Island (Azores Archipelago, Portugal) in September 2015.
 Methods: This new taxon was compared to other diatom species of the genera Nitzschia , Tryblionella , Entomoneis and Hantzschia and to the other species of the genus Platichthys . The morphology is documented by light and scanning electron images and discussed in detail.
 Results: Platichthys furnensis was found in a thermal pool, a similar habitat to the one where P. krammeri type was collected in Chile in 1940. P. furnensis has many structures that are characteristic of the recently described genus Platichthys, including raised canal raphe and fibulae, compressed valve face, steep valve face and numerous open copulae.
 Conclusions: The description of the new taxon is interesting because it is the first species within Platichthys to be described from the Northern Hemisphere.

Stephanodiscus coruscus sp. nov., a new species of diatom (Bacillariophyta) from June Lake, California (USA) with close affiliation to Stephanodiscus klamathensis

Modern and fossil populations of a Stephanodiscus Ehrenberg species from June Lake, California (USA) were analysed using light and scanning electron microscopy (SEM). Stephanodiscus valves were a major constituent of almost all analysed samples, often dominating fossil assemblages dating back several thousand years. The most commonly observed Stephanodiscus specimen in the samples bore a striking resemblance to the extinct Late Pliocene species Stephanodiscus klamathensis, particularly under light microscopy. The population size range, ultrastructure, and other defining characteristics closely matched published information on S. klamathensis. However, under SEM, internal views of the specimens from June Lake showed an important difference; specimens lacked valve face fultoportulae, whereas S. klamathensis is characterized by the presence of two valve face fultoportulae, each with three satellite pores near the centre of the valve. Additional differences in valve size range, absence of fultoportulae on the valve face, and the fact that S. klamathensis is an extinct species (observed in diatomites deposited from Late Pliocene to Pleistocene) with no closely related living relatives, necessitates describing this Stephanodiscus as a new species. To date, Stephanodiscus coruscus has been observed only in June Lake, California; most Stephanodiscus that share strong morphological similarities to this species have only been observed in ancient fossil diatomites. Thus, Stephanodiscus coruscus Jeff. R. Stone, Edlund & Streib sp. nov. is not only a new species but also provides a rare glimpse into the likely types of environments that S. klamathensis and other similar ancient Stephanodiscus may have inhabited in the late Pliocene. Character variations between S. coruscus and S. klamathensis reveal potential patterns of evolution in freshwater lineages, such as character loss, over time.

The Impact of Material Selection on Durability of Exhaust Valve Faces of a Ship Engine – A Case Study

The Impact of Material Selection on Durability of Exhaust Valve Faces of a Ship Engine – A Case Study

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.

Paralia kawasumii sp. nov., a new fossil Paralia species with an elliptical valve from upper Holocene coastal sediments of the central Ise Plain, central Japan

A new fossil diatom species, Paralia kawasumii Sato sp. nov., has been found in upper Holocene coastal sediments of the central Ise Plain, central Japan. Detailed examination by light and scanning electron microscopy showed that P. kawasumii is a straight, chain-forming diatom characterized by double heterovalvy and spathulate linking spines. Like P. elliptica Garcia, its valve face is elliptical and undulate, and parallel and anastomosing ridges and grooves are present on sibling valve faces. Both species together comprise the ‘Paralia elliptica group’. However, P. kawasumii is considered a separate species from P. elliptica because of morphological differences in the structure and position of the rimoportulae and in the densities of fenestrae and of slits on the cingulum. Rimoportulae of P. kawasumii are perpendicular to the striae and distributed just below the overhanging mantle edge. Fenestrae and slits on the cingulum of P. kawasumii are more densely distributed than in P. elliptica. Paralia kawasumii is associated with loose sandy bottoms in intertidal areas (tidal flats to shallow outer bay environments). It is possible that P. kawasumii is an extant species, although no living cells have been found in surface sediments in Japan. If this were the case, P. kawasumii would be the fifth extant Paralia species in Japan.

Analysis and critical evaluation of structural features in four Cymbellaceae taxa from New Caledonia

Delicatophycus costei (Lange-Bertalot et Moser) Wynne, Cymbella bourrellyi Maillard, Cymbella latarea Maillard and Cymbella pernodensis Maillard are endemic to New Caledonia and show uncommon morphological features compared to the sensu stricto definition of their respective genus. Delicatophycus costei was described based on light microscopy and scanning electron microscopy (SEM) observations, confirming the generic LM diagnosis. However, the external view in SEM is atypical as both valve face and mantle are covered by longitudinal ribs, overlaying part of the zig-zag striae, generally accepted as the determinant generic feature. The three species of Cymbella have both apical pore fields and stigmata. However, they show some specific morphological features compared to the more classically shaped Cymbella species. Cymbella bourrellyi has a narrow hyaline area on the valve face and the areolae are bordered internally by small outgrowths. Cymbella pernodensis is distinguished by internal biseriate striae. The internal morphology of Cymbella latarea is characteristic in having typical biseriate striae and bisected apical pore fields. In these three species, internally, the stigmata are continuous with the striae and appear as simple and only weakly separated structures at the end of the striae. The three species are also characterized by differences in the number of areola rows per stria externally and internally.

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

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

Melosira jeanbertrandiana, a new Melosira species (Bacillariophyceae) from the sub-Antarctic region

ABSTRACTDuring a survey of the soil diatom flora of the sub-Antarctic Ile de la Possession (Iles Crozet), located in the southern Indian Ocean, an unknown Melosira species was found that could not be identified using the currently available literature on the genus. The species is described as Melosira jeanbertrandiana sp. nov. based on detailed light and scanning electron microscopy observations. The new species is characterized by a relatively high mantle, the presence of several marginal rings of acute, never bifurcating spines and a series of eight rimoportulae near the central area with several others scattered over the rest of the valve face and mantle. The girdle comprising several large, ligulate open copulae and the position of the rimoportulae clearly place this new species within the genus Melosira C.Agardh. The species was observed in bare, moist soil in scratches in cliffs bordering the ocean where the influence of sea spray is obvious. The description of this new species further increases the number of species of the Melosirales compared to other centric freshwater diatoms which are infrequently found on the sub-Antarctic islands.

Neidium vietnamensis – a new diatom species (Bacillariophyceae: Neidiaceae) from Vietnam and a checklist of the genus from Southeast Asia

A new species, Neidium vietnamensis sp. nov., is described from Phú Quóc Island, South Vietnam, Southeast Asia. The valves of this new species have a distinct linear outline with non-protracted, weakly cuneate ends and longitudinal canals that are bowed and extend towards the middle of the valve face. The areolae forming the striae are covered externally by volate projections that have a reticulated design. A detailed description of this new species is presented, based on light and scanning electron microscopy. A short review of research studies on Neidium in Southeast Asia complements this study, and a checklist of Neidium taxa previously reported from Southeast Asia is given.