Raphe Canal Research Articles

Entomoneis grisslehamnensis, a New Diatom (Bacillariophyceae) from the Baltic Coast of Sweden with taxonomic and ecological notes on Entomoneis paludosa (W. Smith) Reimer

The diatom genus Entomoneis includes species with panduriform frustules characterized by a bilobate, elevated keel, sigmoid raphe canal and numerous open, porous girdle bands. During a phytoplankton survey along the Baltic coast of Sweden, we observed numerous Entomoneis cells, some belonging to the well-known Entomoneis paludosa, while others remained unknown. Morphological and ultrastructural studies of the unknown species were performed with light microscopy (LM), scanning (SEM) and transmission (TEM) electron microscopy, and revealed a unique set of morphological characters. Live cells of Entomoneis grisslehamnensis sp. nov. contain one plate-like plastid and show various degrees of torsion about the apical axis. Microscopic features of cleaned frustules are discussed in comparison with similar species. Most importantly, every 2nd to 5th virga is strongly elevated, uniseriate striae are composed of quadrangular areolae with finely perforated hymenes; the winged keel with a discernible raphe canal is structurally strengthened by raphe fibulae with a flattened wing area, and the main part of the valve bulges towards the margins; striation is decussate on the wings and there is one row of raphe canal areolae at the central area. In addition to describing this new species of an underappreciated, yet cosmopolitan diatom genus, we contribute to the taxonomy of E. paludosa with LM, SEM and TEM details, some of which were not sufficiently noted in original descriptions or re-examination of type material and other specimens made by Dalu et al. [2015. A re-examination of the type material of Entomoneis paludosa (W. Smith) Reimer and its morphology and distribution in African waters. Fottea 15: 11–25] and Long et al. [2022. Ultrastructure of three species of Entomoneis (Bacillariophyta) from Lake Qinghai of China, with reference to the external areola occlusions. PhytoKeys 189: 29–50. doi:10.3897/phytokeys.189.78149].

Morphology, ultrastructure and phylogeny of Auricula weizhouensis sp. nov. (Bacillariophyceae) from the South China Sea

ABSTRACT A new marine diatom species, Auricula weizhouensis sp. nov., was isolated from Weizhou Island, Guangxi, China, and the morphology was examined in detail. The frustule was symmetrical and quadrate, with four rounded angles. The valve was longitudinally reniform. The vegetative cells of A. weizhouensis were 28.9–35.0 μm in length and 22.2–28.9 μm in width. The mature cingulum was composed of five to six open bands. A large plate-like chloroplast was observed on the ventral side of the girdle. There were 5–7 poroids per 1 μm in a row along the median line. The number of radiate and biforked striae was 15–19 per 10 μm on the ventral margin and 21–31 per 10 μm on the dorsal margin. Striae were biseriate with two rows of areolae (12–14 areolae per 1 μm). Both sides of the double-sigmoid raphe canal had a longitudinal costa. Approximately 21–31 fibulae per 10 μm were arrayed in a row on each longitudinal costa. More importantly, A. weizhouensis and Auricula densestriata could be distinguished from other Auricula species by their characteristic concave ventral margin, and the ventral margin of A. weizhouensis was approximately straight in the middle, whereas that of A. densestriata was inflected. In addition, molecular data from partial SSU rDNA sequences showed that A. weizhouensis (strain WZ-1704-E8) belonged to the genus Auricula, with Auricula complexa (KX120684) as the nearest neighbour (4.58% p-distance). Therefore, both morphological and phylogenetic analyses supported A. weizhouensis as a new species.

Fallacia fawensis sp. nov., a new brackish water diatom (Bacillariophyceae) from Southern Iraq

The diatom genus Fallacia includes species having a conopeum which is a perforated thin sheath of silica lying along the apical axis on the external valve face and a hyaline lateral area in the internal valve face. In surveying the benthic diatoms of Basra, a new small brackish water species, Fallacia fawensis was found associated with fine-grained substrata on the western bank of Shatt Al–Arab River, Southern Iraq. This epipelic species is described based on light and scanning electron microscopy and characterized by having a porous conopeum covering the area between raphe sterna and mantle, narrow elongated marginal striae, and a structure similar to lateral hyaline areas in the valve internal side. The terminal raphe endings on the external valve face, below valve apex, the raphe sternum inner margins come close to each other, blocking raphe canal but leaving a lacuna-like thin groove for connection with the deflected upper part of the open raphe canal. These features separated this species from allied taxa of the genus and also from closely related genera, Pseudofallacia and Germaniella. Notes on the ecology and distribution of the new species as well as the associated diatom taxa are provided.

A New Nitzschia Hassall Species (Bacillariaceae, Bacillariophyta) from Saline Ponds in Serbia

In the present study, a new species, Nitzschia haloserbica Vidaković, Ector, C.E.Wetzel & Krizmanić, sp. nov., is described from alkaline saline ponds and channels from Vojvodina Province (Serbia). In 2019 the new species was found in four saline ponds: Bela Bara, Čoka Kopovo, Velika Rusanda and Slatina. The same species was recorded four years ago in saline lakes in Hungary, but the authors listed it as Nitzschia sp. 2. The sigmoid valve outline of the new Nitzschia Hassall species is similar to N. austriaca Hust. but differs in striae density and fibulae distribution. In N. haloserbica sp. nov. the transapical striae are so dense that they are not visible in light microscopy. Both species have fibulae that are quite regularly distributed along the raphe canal, but in N. austriaca the central two fibulae are more widely spaced, reflecting the presence of central raphe endings, which are absent in N. haloserbica sp. nov. At the type locality (Bela Bara) both species were found with relative abundances of 94.93 % for N. haloserbica sp. nov. and 1.21 % for N. austriaca (of the 400 valves counting per slide). The valve morphology, ultrastructure and autecology of the new species are discussed and compared with morphologically similar taxa.

Ultrastructure of three Species of Entomoneis (Bacillariophyta) from Lake Qinghai of China, with reference to the external areola occlusions.

Three sympatric Entomoneis species, found at the same specific locality in Lake Qinghai, China, are studied by using light and scanning electron microscope. Two species are proposed as new to science and named as E.sinensis sp. nov. and E.qinghainensis sp. nov. The third species is identified as E.paludosa (W. Smith) Reimer. Entomoneissinensis has a linear-lanceolate valve outline and Ƨ-shaped keel, bears two distinct 8-shaped loops formed by the valvocopula pars media in each cell and each of its stria is composed of either a long hymen strip or a long hymen strip plus one separated areola close to the raphe. Its hymen strip belongs to Type Two, which is a siliceous membrane strip perforated by two rows of linear pores next to transapical costae and two rows of rounded pores between these two rows of linear pores. Entomoneisqinghainensis has large cells, very high keel and evident hymen strip regions like a U-shaped neck pillow at the middle of valve face. Its hymen strip belongs to Type One, which is a siliceous membrane strip perforated by irregularly distributed round pores. Entomoneispaludosa also has the hymen strip regions that are worm-like and close to the raphe canal. Its hymen strip is same as that of E.qinghainensis. The two kinds of the outside areola occlusions in Entomoneis are compared, summarised and discussed.

Diatoms of the Northeastern Gulf of Mexico: Light and Electron Microscope Observations of Sulcatonitzschia, a new Genus of Nitzschioid Diatoms (Bacillariales: Bacillariaceae) with a Transverse Sulcus

During a systematic investigation of phytoplankton assemblages in the northeastern Gulf of Mexico (GOM) in the aftermath of the Deepwater Horizon blowout we encountered a population of diatoms morphologically similar to Nitzschia ossiformis (Taylor) Simonsen located about 75 km offshore and concentrated at a depth of 60—120 meters. The density of individuals in the population was sufficient to make detailed observations using light and electron microscopy. Our specimens were frequently united into short ribbon—like colonies. This, plus features of the fine structure of valve (biseriate striae, raphe canal without pores and flush with the valve surface) suggest the GOM population is more closely related to Fragilariopsis than to Nitzschia sensu stricto. The presence of a unique feature, described here for the first time, a transverse sulcus in the exterior surface of one of the poles, coupled with the characteristic shape of the valve, suggest our taxon cannot be accommodated in Fragilariopsis, or any other genus hitherto known within the family Bacillariaceae. We, therefore, propose a new genus, Sulcatonitzschia for this diatom and any other nitzschioid diatom with a transverse sulcus, with a new species, Sulcatonitzschia novossiformis as the generitype. Published descriptions suggest that some populations identified as Nitzschia ossiformis may be conspecific with S. novossiformis, but the type of N. ossiformis as delineated by Taylor is not. Examination of the fine structure of the valves is necessary to resolve these relationships.

Ripe for reassessment: A synthesis of available molecular data for the speciose diatom family Bacillariaceae

The Bacillariaceae is a very species-rich family of raphid diatoms and includes the large and taxonomically difficult genus Nitzschia, whose species are often small-celled and finely structured and have few discrete morphological characters visible in the light microscope. The classification of Nitzschia is still mostly based on one developed in the second half of the 19th century by Grunow, who separated the genus into a series of sections largely on cell shape and symmetry, the position of the raphe, transverse extension of the fibulae, and folding of the valve. We assembled and analysed single-gene and concatenated alignments of nSSU, nLSU, rbcL, psbC and cox1 to test Grunow’s and subsequent classifications and to examine selected morphological characters for their potential to help define monophyletic groups. The maximum likelihood trees were equivocal as to monophyly of the family itself but showed good support for each of eight main clades of Bacillariaceae, three of which corresponded more or less to existing genera (Hantzschia, Cylindrotheca and Bacillaria). The other five main clades and some subclades comprised groups of Nitzschia species or assemblies of Nitzschia species with other genera (Pseudo-nitzschia, Fragilariopsis, Neodenticula, Tryblionella, Psammodictyon). Relationships between most of the eight main clades were not resolved robustly but all analyses recovered Nitzschia as non-monophyletic. The Grunowian classification of Nitzschia into sections was not supported, though in some respects (e.g. treatment of sigmoid species) it is better than subsequent reclassifications. Several of the main clades and subclades are cryptic (lacking morphological synapomorphies) and homoplasy is common in both light microscopical and ultrastructural characters (to the extent that organisms initially assigned to the same species sometimes prove to belong to a different main clade). Nevertheless, some characters, including the structure of the raphe canal and girdle, seem to be sufficiently conservative evolutionarily to give a provisional estimate of relationships if molecular data are unavailable. No new formal classifications are proposed but various options are explored and research needs identified.

Entomoneis annagodhei sp. nov., a new marine diatom (Entomoneidaceae, Bacillariophyta) from the west coast of Sweden

The genus Entomoneis includes diatoms with an elevated bilobate keel, a sigmoid raphe canal and numerous girdle bands. It is known to inhabit various environments, from freshwater to marine, both plankton and benthos. During a phytoplankton investigation in the Kungälv estuary on the west coast of Sweden, we observed numerous cells belonging to Entomoneis. Further morphological investigations performed with light and electron microscopy allowed us to describe Entomoneis annagodhei, sp. nov., with a unique set of morphological characters. Most importantly, a still undocumented character proved to be an oblique transapical fascia across the centre of the valve. Other distinctive features of this species are a pronounced raphe canal with dense raphe fibulae, very fine striation, resolvable only with electron microscopy, external lanceolate slit-like opening of the central nodule, and fine, linear to undulate external ridges running more or less parallel and adjacent to the raphe and valve margin. The morphological characters and morphometry are discussed in comparison with similar taxa. Our results contribute to the under-appreciated diversity of Entomoneis, especially inhabiting the marine plankton.

Nitzschia fenestralis: A new diatom species abundant in the Holocene sediments of an eastern African crater lake

Nitzschia is common in the phytoplankton of several East African lakes. A new species, Nitzschia fenestralis, sp. nov. D. Grady, D.G. Mann et Trobajo was encountered at numerous depths in a 16 m sediment core from Lake Babogaya, Ethiopia and is described using light and scanning electron microscopy. It is compared with several other morphologically similar taxa described from East and Central Africa (especially N. aequalis, N. mediocris, N. obsoleta and N. fabiennejansseniana), and from Europe (N. fruticosa). An unusual feature of some of these species (N. fenestralis, N. obsoleta and N. fabiennejansseniana) is that in the raphe canal each stria is represented by two narrower areolae (alternatively interpreted as a single subdivided areola). It is this feature that suggested the name of the new species (through the resemblance to a series of sash windows). Another characteristic of N. fenestralis and N. obsoleta, apparently never reported previously in any diatom, is that the more advalvar bands end approximately halfway along the frustules, rather than at the poles. In most respects (shape and size, stria and fibula densities, valve and girdle structure), N. fenestralis and N. obsoleta are very similar, but confusion is unlikely because they differ in whether central raphe endings are present (N. fenestralis) or absent (N. obsoleta). In Nitzschia fenestralis, and perhaps to a lesser extent in N. obsoleta, the striae usually become strongly radiate towards the poles. A preliminary assessment, based on the literature, suggests that N. fabiennejansseniana may be synonymous with N. obsoleta, which was described earlier.

Simonsenia aveniformis sp. nov. (Bacillariophyceae), molecular phylogeny and systematics of the genus, and a new type of canal raphe system.

The genus Simonsenia is reviewed and S. aveniformis described as new for science by light and electron microscopy. The new species originated from estuarine environments in southern Iberia (Atlantic coast) and was isolated into culture. In LM, Simonsenia resembles Nitzschia, with bridges (fibulae) beneath the raphe, which is marginal. It is only electron microscope (EM) examination that reveals the true structure of the raphe system, which consists of a raphe canal raised on a keel (wing), supported by rib like braces (fenestral bars) and tube-like portulae; between the portulae the keel is perforated by open windows (fenestrae). Based on the presence of portulae and a fenestrated keel, Simonsenia has been proposed to be intermediate between Bacillariaceae and Surirellaceae. However, an rbcL phylogeny revealed that Simonsenia belongs firmly in the Bacillariaceae, with which it shares a similar chloroplast arrangement, rather than in the Surirellaceae. Lack of homology between the surirelloid and simonsenioid keels is reflected in subtle differences in the morphology and ontogeny of the portulae and fenestrae. The diversity of Simonsenia has probably been underestimated, particularly in the marine environment.

Symmetry and sex in Bacillariaceae (Bacillariophyta), with descriptions of three new Nitzschia species

The large diatom genus Nitzschia and the morphologically similar Hantzschia are currently distinguished on the basis of cell symmetry and division. In Hantzschia, the eccentrically placed raphe systems of the two valves are always on the same side of the frustule (‘hantzschioid’ symmetry), never diagonally opposite (‘nitzschioid’ symmetry). Although some Nitzschia species produce hantzschioid cells, it has previously been thought that these cells never breed true but divide to give one nitzschioid daughter and one hantzschioid daughter. Sublittoral marine epipelon from Loch Goil, W Scotland, contained three undescribed species of Bacillariaceae whose cells were always hantzschioid, but which possessed a valve structure (silica flaps on either side of the raphe, no central raphe endings, a slit-like entrance to the raphe canal that narrows towards the poles, and discrete bar-like fibulae) linking them to N. spathulata and the type species of Nitzschia, N. sigmoidea. They also agreed with these species in chloroplast morphology and auxosporulation and are therefore assigned to Nitzschia as N. dicrogramma, N. brachygramma and N. parkii, spp. nov. Consequently the only type of cell division found in all Hantzschia species (in which a hantzschioid parent cell divides to give two hantzschioid daughters) is not unique to Hantzschia but also occurs in at least one lineage of Nitzschia. ‘Core’ Hantzschia species may nevertheless comprise a monophyletic group, characterized by an unusual kind of internal central raphe endings. Four symmetry categories are now known in Hantzschia and Nitzschia: (1) all cells hantzschioid; (2) hantzschioid and nitzschioid cells in a 2 : 1 ratio; (3) hantzschioid and nitzschioid cells in a 1 : 1 ratio; and (4) all cells nitzschioid. The division pattern seems to be constant within species and may therefore be useful as a taxonomic character above the species level. Hantzschia segmentalis is given its first written description.

Morphology and identity of some ecologically important small Nitzschia species

The taxonomy of several small-celled, ecologically significant Nitzschia species, which are frequently confused with each other or whose names are misapplied, is clarified. Following an examination of type material and modern samples by light and electron microscopy, it was concluded that N. frustulum (Kützing) Grunow, N. inconspicua Grunow, N. soratensis E. Morales & Vis and N. invisitata Hustedt are independent species. No morphological basis was found for separating N. frustulum var. subsalina Hustedt or N. boliviana E. Morales & Vis from N. inconspicua and they are therefore placed in synonymy with N. inconspicua. Nitzschia soratensis, described recently from Bolivia, has previously been misidentified in Europe, either as N. inconspicua (from which it differs most obviously in having more bluntly rounded poles, striae within the raphe canal that are composed of triplets, and fibulae that can be seen in light microscopy to widen at their bases) or as N. abbreviata Hustedt ex Simonsen (from which it differs in pore ultrastructure). Nitzschia frustulum resembles N. inconspicua in every morphological feature examined, but with wider valves and consistently higher maximum length.

OVERLOOKED HETEROPOLARITY IN SURIRELLA CF. FASTUOSA (BACILLARIOPHYTA) AND RELATIONSHIPS BETWEEN VALVE MORPHOGENESIS AND AUXOSPORE DEVELOPMENT.

Surirella cf. fastuosa is an apparently isopolar elliptic marine raphid diatom. We observed cells before and after sexual reproduction in monoclonal cultures using light and scanning electron microscopy (LM and SEM). After sexual reproduction cells were approximately twice as large as before, in valve length and width. The stria and infundibula densities were stable during the life cycle. Subtle morphological differences were detectable between the two poles of the frustule. One pole (pole A) was characterized by endings of the external raphe fissure that turned toward the valve face, continuity of the domed wall of the raphe canal externally, an elliptic chamber visible internally, a shallow nick in the interior of the valvocopula. The other pole (pole B) was with the following: straight endings of the external raphe fissures, a dent in the domed wall of the raphe canal externally, a double chamber internally, presence of the open ends of the valvocopula nearby, a deep nick in the valvocopula. Furthermore, at pole A virgae developed at an early stage in morphogenesis, whereas at pole B they were not formed. In the auxospores, pole A was situated beneath the primary transverse perizonial band. Pole A is suggested to be homologous with the head pole in heteropolar Surirella and is the "protopole" likely equivalent to the central nodule in naviculoid taxa. Pole B is homologous with the foot pole in heteropolar Surirella and is the "synaptic pole" formed by fusion of components equivalent to both poles of naviculoid taxa.

Perineal median raphe canal: a typical image

A4 -year-old boy presented at our institution with an anomaly of the perineal median raphe. It was a long and narrow tumefaction developed strictly on the midline on the median raphe between the scrotum and anus. The lesion extended 4 cm and was unilocular (Fig. 1), although cyst enlargement was present at either extremity. Pressure at one extremity was transmitted to the other, reflecting a liquid subcutaneous collection. No inflammatory signs were found. Because of the recent development, total surgical excision was performed with no recurrence. The pathologic examination demonstrated urinary epithelium lining the cyst (Fig. 2). FIGURE 2Histologic examination revealed in some places (arrow) the cyst lined by a urothelium. View Large Image Figure Viewer

The effect of drugs on diatom valve morphogenesis

The effects of various drugs on cell wall (valve) morphogenesis was investigated in three species of diatoms (Pinnularia spp., Surirella robusta, andHantzschia amphioxys) using light microscopy (LM) and scanning electron microscopy (SEM). Treatment ofSurirella with the microtubule (MT) disrupting agent colchicine during early valve formation results in a characteristic malformation of the valve, whereby part of the normally circumferential raphe canal forms as an abnormal protruding lip on the valve surface, located up to ∼ 20 μm from the edge of the valve. The position of this malformed lip coincides with the location of a microtubule center (MC) at the time of colchicine addition, suggesting that the MC may play a direct role in positioning the tip of the raphe canal during valve formation. The migration of this MC to the tip of the cell during early valve morphogenesis is reversibly inhibited by the metabolic inhibitor 2-4-dinitrophenol (DNP). The effect of colchicine onPinnularia valve formation is less severe, causing occasional malformation of the raphe, but little if any lateral displacement. InHantzschia, colchicine has no effect on the positioning of the raphe, but prolonged exposure causes fusion of the raphe canal with the valve face. Cochicine treatment also results in the absence of the normal curvature at the central interruption in the raphe, as well as abnormal pore formation in this central area. Addition of cytochalasin D during early valve formation inHantzschia causes the raphe canal to form in the center of the valve face, suggesting that the normal translocation of the raphe canal to the valve edge is actindependent. Comparison of valves from control and cytochalasintreatmentHantzschia suggest that the pore spacing within the valve is determined by the position relative to the raphe, and does not depend on whether to pores form on the side (mantle) or the face of the mature valve.

An investigation of the involvement of cytoskeletal structures and secretion in gliding motility of the marine diatom, Amphora coffeaeformis

AbstractGliding motility was investigated in the marine diatom, Amphora coffeaeformis. Ultrastructural, biochemical, and pharmacological protocols were employed to probe the possible involvement of cytoskeletal proteins and a secretory process in gliding motility. Motility rate was measured using a video recording apparatus, and the effects of various cytoskeleton‐disrupting drugs on motility were tested. Cytochalasins D and E, podophyllotoxin, and vinblastine (all at 25 μUg/ml) reversibly inhibited motility, as did monensin (10 μUM) and pronase (25 μUg/ml). Biochemical protein analysis of whole‐cell extracts by one‐ and two‐dimensional polyacrylamide gel electrophoresis revealed polypeptides comigrating with rabbit skeletal muscle actin and bovine brain tubulin; however, specific assays used to separate actin from whole‐cell preparations gave ambiguous results. Ultrastructural studies revealed the presence of extracellular material between the raphe canal and the substratum in motile cultures. An assay was devised for the detection of radioactively labeled material (MW > 1800 Daltons) released by motile cultures into the culture medium. When cultures were treated with either an anticytoskeletal drug or monensin, motility was inhibited while the amount of measured radioactivity increased over solvent‐treated control groups. The results from this study indicate possible roles for both actin‐ and tubulin‐based structures in gliding motility of Amphora. Though secretion may be necessary for gliding to occur, its exact relationship to motility was not deduced. The data obtained in this study are compatible with a theory for the mechanism of gliding which involves the surface translocation of externally exposed membrane proteins against an immobile matrix of substratum‐attached secreted material to generate the force required for movement.

VALVE MORPHOGENESIS AND THE MICROTUBULE CENTER IN THREE SPECIES OF THE DIATOM NITZSCHIA1

ABSTRACTThe relationship of cell organelles to valve morphogenesis was investigated in three species of Nitzschia. One, N. sigmoidea (Nitzsch) W. Sm., showed consistent ability to generate both nitzschioid and hantzschioid symmetry in daughter cells following cytokinesis; the other two maintained nitzschioid symmetry stably. From previous work with Hantzschia, a certain sequence of events could be anticipated in the cytoplasm. In two significant areas–the behavior of the Microtubule Center (MC) and its microtubule (MT) system, and the central origin of the silicalemma–not only were the results unexpected, but the three species showed fundamental differences among themselves. In N. sigmoidea, the silicalemma (and the future raphe region) arises centrally on the cleavage furrow, and after some lateral expansion, the silicalemmas and their associated organelles move in opposite directions in daughter cells, so that the raphe and the raphe canals end up along the girdle side of the cell as expected. However, the MCs never become associated with their silicalemma, remaining throughout near the girdle bands. In N. sigma (Kütz) W. Sm., the silicalemmas arise centrally and after lateral growth, move in opposite directions to generate nitzschioid symmetry. In this case, the MCs move to the vicinity of but never close to the silicalemmas, and follow them distantly during their lateral movement. In N. tryblionella Hantzsch, the new silicalemmas arise opposite one another, on one side of the daughter cells; each MC soon moves very close to its silicalemma, and remains thus through most of valve morphogenesis. Later, only one silicalemma/MC complex moves laterally, establishing the nitzschioid symmetry in both daughter cells. In all three species, as in Hantzschia, linear arrays of mitochondria aligned along MTs occupy the forming raphe canal, and microfilaments line the outer edge of the expanding silicalemma. The fibulae (the wall struts arching across the raphe canal) in Hantzschia always grow from the valve surface to the girdle surface of the forming valves. In these three Nitzschiae, this invariably happens in only one daughter cell of any pair; in the other, all the fibulae grow from the girdle surface to the valve surface. An explanation of these variations is proposed: that the morphogenetic machinery of Nitzschia and Hantzschia have a common origin, with present Nitzschiae having undergone considerable diversification at the intracellular level, causing the unstable cell symmetry exhibited by several modern species. Perhaps a taxonomic distinction between Hantzschia and Nitzschia lies in whether the morphogenetic machinery associated with valve morphogenesis moves laterally in the same or in opposite directions.