Rows Of Poroids Research Articles

<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.

Two New and Nontoxigenic Pseudo-nitzschia species (Bacillariophyceae) from Chinese Southeast Coastal Waters.

To explore the species diversity and toxin profile of Pseudo-nitzschia, monoclonal strains were established from Chinese southeast coastal waters. The morphology was examined under light and transmission electron microscopy. The internal transcribed spacer region of ribosomal DNA was sequenced for phylogenetic analyses, and the secondary structure of ITS2 was predicted and compared among allied taxa. A combination of morphological and molecular data showed the presence of two new species, Pseudo-nitzschia hainanensis sp. nov. and Pseudo-nitzschia taiwanensis sp. nov. Pseudo-nitzschiahainanensis was characterized by a dumpy-lanceolate valve with slightly blunt apicesand a central nodule, as well as striae comprising two rows of poroids. Pseudo-nitzschiataiwanensis was characterized by a slender-lanceolate valve, and striae comprising one row of split poroids. The poroid structure mainly comprised two sectors. Both taxa constituted their own monophyletic lineage in the phylogenetic analyses inferred from ITS2 rDNA and were well differentiated from other Pseudo-nitzschia species. Morphologically, P.hainanensis and P.taiwanensis could be assigned to the Pseudo-nitzschia delicatissima and the Pseudo-nitzschia pseudodelicatissima complex, respectively. Particulate domoic acid was measured using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS), but no detectable pDA was found. With the description of the two new species, the species diversity of genus Pseudo-nitzschia reaches 58 worldwide, among which 31 have been recorded from Chinese coastal waters.

Diversity and distribution of nanoplanktonic Minidiscus (Bacillariophyta) in shelf waters of the Southwest Atlantic Ocean

Minidiscus Hasle is a genus of small sized diatoms comprising about eight nanoplanktonic marine species. Renewed interest in this genus has arisen since recent investigations recorded a fairly high contribution of some species to the phytoplankton biomass on a global scale. In Brazil, very few studies have been performed, and only two species of Minidiscus have been reported over the 8500 Km coastline. In this paper, we report five species found in Southeast and South Brazilian waters: Minidiscus alphacrucis sp. nov., M. chilensis, M comicus, M. trioculatus, and M. variabilis (also the variety inornata). One of the tiniest diatom ever described, the new species M. alphacrucis has poroidal areolae, which are organized in radial striae with two rows of poroids, conspicuously limited by the interstriae. Minidiscus alphacrucis is compared with other morphologically similar species. In addition, the world distribution of the extant Minidiscus species is reviewed and discussed.

Occurrence of Pseudo-nitzschia species and associated domoic acid production along the Guangdong coast, South China Sea

The diatom genus Pseudo-nitzschia, which has been associated with amnesic shellfish poisoning events globally, is also one of the key harmful microalga groups in Guangdong coastal waters, off the north coast of the South China Sea. In order to explore the diversity and toxigenic characteristics, Pseudo-nitzschia isolates were established. Based on a combination of morphological and molecular features, in total 26 different Pseudo-nitzschia taxa were identified, including two new species, P. uniseriata H.C. Dong & Yang Li and P. yuensis H.C. Dong & Yang Li. Morphologically, P. uniseriata is unique by having striae mainly comprising one row of poroids, which are simple without divided hymen internally, and each poroid containing one, seldom two sectors. Pseudo-nitzschia yuensis is characterized by having striae comprising one to two rows of poroids. In biseriate striae, the poroids are polygonal and irregularly distributed, and a discontinuous row of poroids may be present in the middle. In uniseriate striae, the poroids usually contain 1–5 sectors. Both taxa are well differentiated from other Pseudo-nitzschia species in phylogenetic analyses inferred from ITS2 sequence-structure information. Pseudo-nitzschia uniseriata is sister to P. lineola, whereas P. yuensis forms a group together with P. micropora and P. delicatissima. When comparing ITS2 secondary structure, two hemi-compensatory base change (HCBCs) are found between P. uniseriata and P. lineola. One compensatory base change (CBC) and four HCBCs are found between P. yuensis and P. delicatissima, and there is one CBC and five HCBCs between P. yuensis and P. micropora. The ability of cultured strains to produce particulate DA (pDA) revealed production of pDA in twenty-nine strains belonging to seven species: P. bipertita, P. caciantha, P. cuspidata, P. fraudulenta, P. fukuyoi, P. lundholmiae and P. multiseries. This is the first report of P. bipertita being toxic, with pDA content of 15.6 ± 2.1 fg cell–1. The presence of brine shrimps significantly increased pDA content in P. cuspidata, P. fukuyoi, P. lundholmiae and P. multiseries 1.4 to 7 times, and induced pDA production in P. fraudulenta from below detection limit to 17.5 ± 1.6 fg cell–1. The highest pDA concentration, 4830.5 ± 120.3 fg cell–1, was detected in P. multiseries, a level much lower than previous reports on P. multiseries from North America and Europe. Overall, the cellular toxin levels in Pseudo-nitzschia spp. were low in Guangdong coastal isolates.

Three New Species of Ulnaria (Kützing) Compère (Bacillariophyta) from China, with Reference to the Fine Structure of Their Valvocopula

Three new species of Ulnaria (Kutzing) Compere are described based on light and scanning electric microscopy observations. Ulnaria oxybiseriata D.M. Williams & Bing Liu, sp. nov., has linear-lanceolate to lanceolate valves with apiculate and produced ends, biseriate striae, and a central area mostly forming an incomplete fascia surrounded by shortened striae on one side. Ulnaria jinbianensis S. Blanco & Bing Liu, sp. nov., bears linear-lanceolate valves with rostrate to subrostrate ends in larger valves and cuneate ends in smaller valves, uniseriate stria, and a central area forming a rectangular to trapezoid fascia. Ulnaria dongtingensis Bing Liu, sp. nov., possesses a narrow-lanceolate valve outline with produced rostrate to capitate ends, uniseriate stria, and a central area forming almost square fascia. The valvocopula of all three new species bears the same ultrastructure: 1) a complete valvocopula is a closed ring with the same shape as the valve outline, closely attached to the mantle interior surrounding the valve margin; 2) each valvocopula present a row of poroids which bisects the pars interior and exterior; 3) valvocopula with sawtooth-shaped projections attached to the valve over virgae internally; and 4) the valvocopula closed and hyaline at both apices. All three species were found in alkaline freshwater (around pH 8) with moderate conductivity (c. 102-221 µS/cm).

Species composition and toxicity of the genus Pseudo-nitzschia in Taiwan Strait, including P. chiniana sp. nov. and P. qiana sp. nov.

In a field survey in the Taiwan Strait during April 2016, the species composition and the domoic acid production of the diatom genus Pseudo-nitzschia were investigated. A total of 80 strains of Pseudo-nitzschia were established, and species identification was determined based on a combination of morphological and molecular data. Fourteen taxa were recognized, i.e., P. americana, P. brasiliana, P. calliantha, P. cuspidata, P. galaxiae, P. lundholmiae, P. multiseries, P. multistriata, P. pseudodelicatissima, P. pungens var. aveirensis, P. pungenus var. pungens and P. sabit, as well as two novel species P. chiniana C.X. Huang & Yang Li and P. qiana C.X. Huang & Yang Li. Morphologically, P. chiniana is characterized by striae comprising one or two rows of poroids, and valve ends that are normally dominated by two rows of poroids within each stria. Whereas P. qiana is unique by having a narrow valve width (1.3–1.5 μm) and sharply pointed valve ends. Both taxa constitute their own monophyletic lineage in the phylogenetic analyses inferred from LSU and ITS2 rDNA, and are well differentiated from other Pseudo-nitzschia species. Pseudo-nitzschia chiniana forms a group with P. abrensis and P. batesiana in LSU and ITS trees, whereas P. qiana is sister to P. lineola. When comparing ITS2 secondary structure, five CBCs and seven HCBCs are recognized between P. chiniana and P. abrensis, and four CBCs and ten HCBCs between P. chiniana and P. batesiana. Two CBCs and eight HCBCs are found between P. qiana with P. lineola. The ability of the strains to produce domoic acid was assessed, including a potential toxin induction by the presence of brine shrimps. Results revealed production of domoic acid in six strains belonging to three species. Without presence of brine shrimps, cellular DA (pDA) was detected in four P. multiseries strains (1.6 ± 0.3, 26.6 ± 2.7, 68.3 ± 4.2 and 56.9 ± 4.7 fg cell−1, separately), one strain of P. pseudodelicatissima (0.8 ± 0.2 fg cell−1) and one strain of P. lundholmiae (2.5 ± 0.4 fg cell−1). In the presence of brine shrimps, pDA contents increased significantly (p < 0.05) in P. lundholmiae (strain MC4218) and P. multiseries (strain MC4177), from 2.5 ± 0.4 to 8.9 ± 0.7 and 1.6 ± 0.3 to 37.2 ± 2.5 fg cell−1 respectively.

A new diatom species P. hallegraeffii sp. nov. belonging to the toxic genus Pseudo-nitzschia (Bacillariophyceae) from the East Australian Current

A new species belonging to the toxin producing diatom genus Pseudo-nitzschia, P. hallegraeffii sp. nov., is delineated and described from the East Australian Current (EAC). Clonal cultures were established by single cell isolation from phytoplankton net hauls collected as part of a research expedition in the EAC region in 2016 on the RV Investigator. Cultures were assessed for their morphological and genetic characteristics, their sexual compatibility with other Pseudo-nitzschia species, and their ability to produce domoic acid. Light and transmission electron microscopy revealed cells which differed from their closest relatives by their cell width, rows of poroids, girdle band structure and density of band straie. Phylogenetic analyses based on sequencing of nuclear-encoded ribosomal deoxyribonucleic acid (rDNA) regions showed this novel genotype clustered within the P. delicatissima complex, but formed a discrete clade from its closest relatives P. dolorosa, P. simulans, P. micropora and P. delicatissima. Complementary base changes (CBCs) were observed in the secondary structure of the 3’ nuclear ribosomal transcribed spacer sequence region (ITS2) between P. hallegraeffii sp. nov. and its closest related taxa, P. simulans and P. dolorosa. Under laboratory conditions, and in the absence of any zooplankton cues, strains of P. hallegraeffii sp. nov. did not produce domoic acid (DA) and were not sexually compatible with any other Pseudo-nitzschia clones tested. A total of 18 Pseudo-nitzschia species, including three confirmed toxigenic species (P. cuspidata, P. multistriata and P. australis) have now been unequivocally confirmed from eastern Australia.

Pseudo-nitzschia simulans sp. nov. (Bacillariophyceae), the first domoic acid producer from Chinese waters

The genus Pseudo-nitzschia has attracted attention because of production of the toxin, domoic acid (DA), causing Amnesic Shellfish Poisoning (ASP). Pseudo-nitzschia blooms occur frequently in Chinese coastal waters, and DA has been detected in several marine organisms, but so far no Pseudo-nitzschia strains from Chinese waters have been shown to produce DA. In this study, monoclonal Pseudo-nitzschia strains were established from Chinese coastal waters and examined using light microscopy, electron microscopy and molecular markers. Five strains, sharing distinct morphological and molecular features differentiating them from other Pseudo-nitzschia species, represent a new species, Pseudo-nitzschia simulans sp. nov. Morphologically, the taxon belongs to the P. pseudodelicatissima group, cells possessing a central nodule and each stria comprising one row of poroids. The new species is characterized by the poroid structure, which typically comprises two sectors, each sector located near opposite margins of the poroid. The production of DA was examined by liquid chromatography tandem mass spectrometry (LC–MS/MS) analyses of cells in stationary growth phase. Domoic acid was detected in one of the five strains, with concentrations around 1.05–1.54 fg cell−1. This is the first toxigenic diatom species reported from Chinese waters.

Taxonomy, morphology and distribution of Cymatosiraceae (Bacillariophyceae) in the littorals of Santa Catarina and Rio Grande do Sul

Species of Cymatosiraceae (diatoms) studied from Santa Catarina and Rio Grande do Sul littorals: Campylosira cymbelliformis, Cymatosira belgica, Cymatosirella minutissima, Plagiogrammopsis minima and Plagiogrammopsis vanheurckii) are presented with a morphological description, dimension data, distribution in the studied area and are illustrated in light microscope, and scanning and transmission electron microscopes. Superficial sand samples from the swash zone and plankton were collected from over 30 marine sandy beaches. Cymatosirella minutissima and Plagiogrammopsis minima are new recordings in Brazil widening their distribution to South America, previously being restricted to Europe. Campylosira cymbelliformis was the species most often observed in plankton samples and Plagiogrammopsis minima in sediment samples. Cymatosira belgica and Plagiogrammopsis minima were recorded as abundant species in Mariscal, Quatro Ilhas and Zimbros reaching a relative frequency of 9.6%. The study adds new morphological data to some taxa as the presence of rimoportula on C. minutissima and one row of poroids on copulae of P. minima, these features being in agreement with Cymatosiraceae diagnosis.

THALASSIONEIS SIGNYENSIS (BACILLARIOPHYCEAE) FROM NORTHWEST WEDDELL SEA ICEBERGS, AN EMENDATION OF THE GENERIC DESCRIPTION(1).

We offer an emended description of the genus Thalassioneis based on new observations of the type species, T. signyensis Round, from material sampled in the northwest Weddell Sea. Specimens from algal communities attached to submerged flanks of several icebergs were collected with a remote-operated vehicle (ROV-Phantom DS 2). The analyses were carried out by LM and SEM. Fresh material and frustules without organic matter allowed us to observe details not included in the original description such as type and structure of colonies and chloroplasts. The frustule shows an asymmetry with respect to the location of the apical pore fields, one of them situated on the valvar face and the other one displaced toward the mantle; the former is involved in joining contiguous cells to form long chains. Furthermore, we present details on the ultrastructure of the cingulum that consists of three to four open copulae with one or more rows of poroids. A brief discussion on the habit and ecology of this taxon, which may be endemic to the northwest Weddell Sea, is also presented. A comparison with similar genera, such as Brandinia, Creania, Fossula, Fragilaria, Rimoneis, Synedropsis, and Ulnaria, is included with an evaluation of morphological characteristics useful to differentiate them.

A DETAILED DESCRIPTION OF A DANISH STRAIN OF NITZSCHIA SIGMOIDEA, THE TYPE SPECIES OF NITZSCHIA, PROVIDING A REFERENCE FOR FUTURE MORPHOLOGICAL AND PHYLOGENETIC STUDIES OF THE GENUS

Nitzschia sigmoidea is the type species of the diatom genus Nitzschia. Recent evidence implies that the genus is polyphyletic. As a reference for future studies of the genus, we here provide a thorough morphological examination of the silica frustule, including new details of copulae and poroids, as well as compiling previously published information on the cellular ultrastructure. Observed specimens of Nitzschia sigmoidea are linear in frustule view and sigmoid in girdle view with a length of 346–359 μm, and a width of 9–13 μm. Both nitzschioid and hantzschioid cells are found. The raphe is highly eccentric, elevated on a keel, without a central nodule. The raphe ends externally in a hook-shaped terminal fissure, internally in a helictoglossa forming an excrescence. Tubular fibulae are slim and irregularly distributed with a density of 6–9 in 10 μm. A conopeum runs the entire length of the cell. The striae are uniseriate with 4–5 poroids in 1 μm, each with a hymen with a hexagonal pattern of perforations. Two types of copulae are found, both with two rows of poroids, 3.2–3.4 poroids in 1 μm. One type of copula is fimbriate with evenly distributed fimbriae, while the other type has a veil. Initially, growth of the diatom was restricted by lack of carbon in the freshwater medium, after addition of bicarbonate it grew well. HPLC analysis showed no domoic acid production by N. sigmoidea.

INTER‐ AND INTRASPECIFIC VARIATION OF THE PSEUDO‐NITZSCHIA DELICATISSIMA COMPLEX (BACILLARIOPHYCEAE) ILLUSTRATED BY RRNA PROBES, MORPHOLOGICAL DATA AND PHYLOGENETIC ANALYSES1

A study of 25 cultures tentatively identified as Pseudo‐nitzschia delicatissima (Cleve) Heiden, and originating from geographically widely distributed locations, showed both morphological and genetic variation among strains. Use of rRNA‐targeted DNA probes on 17 different strains showed large variation in the hybridization patterns. Detailed morphological studies placed the isolates into three groups. The sample on which the neotype of P. delicatissima is based was also examined, and used to establish the morphological identity of P. delicatissima. Phylogenetic analyses of 16 strains, based on sequences of internal transcriber spacer 1 (ITS1), 5.8S and ITS2 of the nuclear‐encoded rDNA, supported the morphological observations and the hybridization studies, and revealed large genetic variation among strains. A combination of the morphological and molecular findings resulted in the description of two new species, P. decipiens sp. nov. and P. dolorosa sp. nov. P. dolorosa has a mixture of one or two rows of poroids in the striae whereas P. delicatissima always has two rows. In addition, P. dolorosa has wider valves and a lower density of poroids. P. decipiens differs from P. delicatissima by a higher density of striae on the valve face as well as a higher density of poroids on the girdle bands. Among the strains referred to P. delicatissima, an epitype was selected. Large genetic variation was found among the P. delicatissima strains and a subdivision into two major clades represent cryptic species.

Fragilariopsis, a newly recorded nanodiatom genus for China

A nanodiatom genus, Fragilariopsis Hustedt, is newly recorded in China. This genus is characterized by, (1) cells in ribbons united by the entire or the greater part of the valve surface, (2) raphe strongly eccentric, (3) approximately equal numbers of interstriae and fibule, (4) apical axis often heteropolar, and (5) striae with two rows of poroids, seldom one or more than two. A detailed description of the taxonomic characteristics of the genus is given. The two species distributed in East China Sea and Huanghai Sea of China, F. kerguelensis (O'Meara) Hustedt and F. rhombica (O'Meara) Hustedt, were observed under TEM and photographed.

OESTRUPIA GRANDIS SP. NOV., A NEW BENTHIC MARINE DIATOM FROM THE BAHAMAS

A new diatom species, Oestrupia grandis Hein & Winsborough, is described from benthic saline habitats on Norman's Pond Cay (Exuma Islands) in the Bahamas. The ends of this lanceolate diatom are cuneate to slightly rostrate. The axial area widens asymmetrically into a unilaterally inflated central area. Alveolate striae are almost parallel at the centre of the valve but become radiate toward the apices. Each stria, except those close to the apices, consists of two alveoli, with the inner alveolus longer than the outer one. Each alveolus opens externally via three transapical rows of poroids.

Fine structure, taxonomy and systematics of Reimerothrix (Fragilariaceae: Bacillariophyta), a new genus of synedroid diatoms from Florida Bay, USA

Reimerothrix floridensis A.K.S.K. Prasad gen. & sp. nov., a monotypic genus of Fragilariaceae (Bacillariophyta), is described from Florida Bay, USA. It forms rosettes of cells and grows epiphytically. The cells are narrowly linear and arcuate or straight and have a single plate-shaped plastid. The valves are inflated at their central part and have greatly elongated, drawn-out ends (projections). The central part of the valve has a wide lanceolate sternum and is almost free of areolation, except at the valve face-mantle junction, where there is a single row of poroid areolae. Over most of the elongate projections the valve bears a single row of areolae, but near the apices the areolae are irregularly distributed in two rows. The polar mantle bears pore fields with two or three rows of poroids, which are larger than those on the valve face, and two to four short spines. A single rimoportula is found at each apex; its external opening is a simple pore and its internal opening is usually orientated perpendicular to the apical axis. The valve mantle is hyaline, except at the apices. The cingulum is composed of two to four open, porous bands. Reimerothrix is compared with genera in the Fragilariaceae and Toxariaceae.