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SEM observations on siliceous microfossil assemblages of Late Cretaceous age from the southwest Pacific revealed the presence of bona fide Parmales. The subspherical tests are similar in morphology...

A re-investigation of phytoplankton assemblages on old membrane filters from polar–subpolar waters has revealed the presence of seven taxa within the Triparma strigata–Triparma verrucosa group (Bol...

A form of Triparma laevis (Parmales, Bolidophyceae), not formally described yet, has been reported in Southern Ocean phytoplankton surveys for more than 30 years. A re-examination of some filtered ...

Antarctic regions are known to be mainly dominated by diatoms in the water column under sea ice. In this study, we report for the first time two distinct phytoplankton blooms dominated by nanoflagellates (< 15 µm) under the landfast ice in Terra Nova Bay during the late spring-early summer 2015-2016. The taxa included the pelagic Bolidophyceae Pentalamina corona, the Chrysophyceae Ochromonas spp. and the Chlorophyceae Chlamydomonas spp., typically found in fresh waters, and the Prymnesiophyceae Phaeocystis antarctica usually observed dominating in polynya areas. These species represented from 40% to 91% of the total phytoplankton community, a percentage contrasting with the prevalence of diatoms found previously. The dominance of nanoflagellates, rather than diatoms, during late spring and early summer may have important implications for trophic relationships in Antarctic waters and the presence of typical freshwater species could indicate a great input of continental waters related to environmental changes.

We present the first draft whole-genome sequence for the Parmales (Bolidophyceae, Heterokonta), a picoplanktonic sister group of diatoms, using a Triparma laevis f. inornata strain that was isolated from the Oyashio region in the western North Pacific Ocean.

Triparma laevis f. inornata is a unicellular alga belonging to the Bolidophyceae, which is most closely related to diatoms. Like diatoms, T. laevis f. inornata has a siliceous cell wall. The cell wall of T. laevis f. inornata consists of four round plates (three shields and one ventral plate) and one dorsal and three girdle plates. But, unlike diatoms, T. laevis f. inornata cells can grow when concentrations of silica are depleted. We took advantage of this ability, using TEM to study the ontogeny of the siliceous plate, pattern center formation, and development. Two types of pattern centers (annulus and sternum) were observed in the early and middle stage of plate formation. During their formation, the annuli were initially crescent-shaped but eventually their ends fused to make a ring. Only outward silica deposition of the branching ribs occurred on the growing annulus until it became a ring, resulting in an unfilled circle inside the annulus. The pattern center of the shield plate was always an annulus, but in ventral plates both annulus and sternum were observed. The annuli and sterna in T. laevis f. inornata round plates were very similar to the annuli and sterna in diatom valves. These results suggested that the round plates of Parmales are homologous to diatom valves. This information on the plate ontogeny of T. laevis f. inornata provides new insights into the evolution of the siliceous cell wall in the Parmales and diatoms.

Despite numerous studies on Parmales (Bolidophyceae) from polar regions, there have been few reports on tropical assemblages, especially on their ecology and diversity. Filtered water samples collected at two hydrocast stations during a 1996–1997 survey of the western Pacific and eastern Indian Ocean were recently investigated and revealed for the first time the presence of tropical Parmales in the Sulu Sea and South China Sea. The absolute abundances of total Parmales were very low (< 1300 cells l−1) and restricted to the deep photic zone (100–150 m). The Sulu Sea assemblages were dominated by Triparma columacea f. longiseta and Triparma laevis f. mexicana, while those in the South China Sea were dominated by Tetraparma silverae. Of the seven taxa encountered at these stations, two are described as new species (Te. silverae and Tetraparma trullifera) and three as new formae (Triparma columacea f. longiseta, Triparma laevis f. fusiformis and Triparma retinervis f. tortispina).

Nearly complete (> 97%) chloroplast-encoded rbcL gene sequences were determined for Bolidomonas mediterranea from the eastern Mediterranean Sea and two strains of B. pacifica var. eleuthera from the equatorial Pacific Ocean. The three sequences were added to an rbcL data matrix comprising 45 taxa representing 11 of the 12 recognized classes of Hetero-kontophyta. Phylogenetic analyses that used maximum parsimony (MP), maximum likelihood (ML) and neighbour-joining (NJ) algorithms supported their sister group relationship to the Bacillariophyceae. Centric and pennate diatoms and the three novel Bolidomonas rbcL sequences share a two-amino-acid insertion at position 1336, relative to the homologous position in the complete sequence for the centric diatom Odontella sinensis. This synapomorphic character state further supports a common evolutionary history of bolidophyceans and diatoms. Chloroplast- and nuclear-encoded molecular markers thus favour the idea that the ancestor of the diatoms possessed tw...

The marine alga Triparma laevis NIES-2565, belonging to the Parmales (Bolidophyceae), possesses a siliceous cell wall that is composed of shield, ventral, dorsal and girdle plates. The cell wall is...

International audience; Pico-and nano-phytoplankton (respectively, 0.2-2 and 2-20 µm in cell size) play a key role in many marine ecosystems. In this size range, Bolidophyceae is a group of eukaryotes that contains species with cells surrounded by 5 or 8 silica plates (Parmales) as well as naked flagellated species (formerly Bolidomonadales). Bolidophyceae share a common ancestor with diatoms, one of the most successful groups of phytoplankton. This review summarizes the current information on taxonomy, phylogeny, ecology, and physiology obtained by recent studies using a range of approaches including metabarcoding. Despite their rather small contribution to the phytoplankton communities (on average less than 0.1%), Bolidophyceae are very widespread throughout marine systems from the tropics to the pole. This review concludes by discussing similarities and differences between Bolidophyceae and diatoms.

Spatial distribution, diversity and composition of eukaryotic ultraplankton community of the northern South China Sea (nSCS) surface water and the relationship with the in situ water environment were investigated by the method of polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). A total of 18 DGGE intensive bands were detected and the sequence analysis of these DGGE bands revealed that Alveolata was the dominant eukaryotic ultraplankton group of surface water in the nSCS (50%). Other species belonged to Bicoecea, Bolidophyceae, Polycystinea and Chlorophyta, which accounted for less proportion of eukaryotic ultraplankton in the study area. Unweighted pair group method with arithmetic averages clustering of the sampling stations indicated that all stations were classified mainly based on geographical proximity. Redundancy analysis (RDA) was employed to further investigate the relationships between DGGE band pattern and the environmental variables. Based on the RDA analysis, temperature, salinity, phosphorus and silicate were the important factors to shape the eukaryotic ultraplankton community composition in the nSCS.

© 2017, Pleiades Publishing, Ltd. The molecular diversity of poorly studied algae of Bolidophyceae class was first estimated by Illumina sequencing of V4 region of 18S rRNA gene in ice, under-ice water and summer water of the subarctic White Sea. We used two clustering thresholds–93 and 97%–and revealed 31 phylotypes of Bolidophyceae. Triparma pacifica and Т. strigata were identified to species level. The association of individual phylotypes to certain biotopes (ice or plankton) and stages of seasonal succession (under ice or summer plankton) has been established. Some phylotypes are found in different biotopes and over a wide temperature range. Due to changing their genetic composition, Bolidophyceae are a constant component of the photoautotrophic plankton and ice communities.

Stramenopiles or heterokonts constitute one of the most speciose and diverse clades of protists. It includes ecologically important algae (such as diatoms or large multicellular brown seaweeds), as well as heterotrophic (e.g. bicosoecids, MAST groups) and parasitic (e.g. Blastocystis, oomycetes) species. Despite their evolutionary and ecological relevance, deep phylogenetic relationships among stramenopile groups, inferred mostly from small-subunit (SSU) rDNA phylogenies, remain unresolved, especially for the heterotrophic taxa. Taking advantage of recently released stramenopile transcriptome and genome sequences, as well as data from the genomic assembly of the MAST-3 species Incisomonas marina generated in our laboratory, we have carried out the first extensive phylogenomic analysis of stramenopiles, including representatives of most major lineages. Our analyses, based on a large dataset of 339 widely distributed proteins, strongly support a root of stramenopiles lying between two clades, Bigyra and Gyrista (Pseudofungi plus Ochrophyta). Additionally, our analyses challenge the Phaeista-Khakista dichotomy of photosynthetic stramenopiles (ochrophytes) as two groups previously considered to be part of the Phaeista (Pelagophyceae and Dictyochophyceae), branch with strong support with the Khakista (Bolidophyceae and Diatomeae). We propose a new classification of ochrophytes within the two groups Chrysista and Diatomista to reflect the new phylogenomic results. Our stramenopile phylogeny provides a robust phylogenetic framework to investigate the evolution and diversification of this group of ecologically relevant protists.

International audience; Bolidomonas is a genus of picoplanktonic flagellated algae that is closely related to diatoms. Triparma laevis, a species belonging to the Parmales, which are small cells with a siliceous covering, has been shown to form a monophyletic group with Bolidomonas. We isolated several novel strains of Bolidophyceae that have permitted further exploration of the diversity of this group using nuclear, plastidial and mitochondrial genes. The resulting phylogenetic data led us to formally emend the taxonomy of this group to include the Parmales within the Bolidophyceae, to combine Bolidomonas within Triparma and to define a novel species, Triparma eleuthera sp. nov. The global distribution of Bolidophyceae was then assessed using environmental sequences available in public databases, as well as a large 18S rRNA V9 metabarcode data set from the Tara Oceans expedition. Bolidophyceans appear ubiquitous throughout the sampled oceans but always constitute a minor component of the phytoplankton community, corresponding to at most ~ 4% of the metabarcodes from photosynthetic groups (excluding dinoflagellates). They are ~ 10 times more abundant in the small size fraction (0.8– 5 μm) than in larger size fractions. T. eleuthera sp. nov. constitutes the most abundant and most widespread operational taxonomic unit (OTU) followed by T. pacifica, T. mediterranea and the T. laevis clade. The T. mediterranea OTU is characteristic of Mediterranean Sea surface waters and the T. laevis clade OTU is most prevalent in colder waters, in particular off Antarctica.

A small siliceous species of marine phytoplankton, order Parmales (Heterokonta), was isolated and characterized for the first time with the aid of a fluorescent silicon tracer 2-(4-pyridyl)-5-([4-(2-dimethylaminoethylaminocarbamoyl)-methoxy]phenyl)oxazole (PDMPO). This dye was easily detected by clear fluorescence in newly produced silica cell plates. Our isolate was surrounded by eight smooth plates without any ornamentation, suggesting a similarity to Triparma laevis B. C. Booth. TEM observation showed the typical ultrastructure of photosynthetic heterokontophytes; with two chloroplast endoplasmic reticulate membranes, a girdle lamella, three thylakoid lamellae, and mitochondrion with tubular cristae. Molecular phylogenetic analyses of SSU rDNA and rbcL genes showed that the parmalean alga was within the bolidophycean clade of autotrophic naked flagellates and a sister group of diatoms. HPLC analysis detected chl a, c1 + c2 , and c3 ; fucoxanthin; and diadinoxanthin as major photosynthetic pigments, and a composition that is shared with Bolidophyceae and diatoms. Together, these data indicate a close evolutionary relationship between Parmales, Bolidophyceae, and diatoms. The PDMPO-staining procedure should accelerate isolation of other Parmales species, helping to establish their diversity and aiding quantitative study of their role in oceanic processes.

Marine photosynthetic picoeukaryotes (PPEs), representing organisms

The microplankton communities on filter samples from three shallow (0–300 m) hydrocasts, conducted in August 1999, January 2000, and May 2000 at Station KNOT in the Western Subarctic Gyre of the NW Pacific, have been analyzed by scanning electron microscopy (SEM). The results clearly show that small (o10mm) phytoplankton, such as coccolithophorids, Parmales, and the pennate diatom Fragilariopsis pseudonana, play important roles in seasonal productivity. The Parmales were the most dominant mineralized phytoplankton group in May and August, and their yearround presence in scaly form suggests they are not cysts as previously thought. As the Parmales are rare or absent in the underlying sediment traps or surface sediments, their siliceous scales are undoubtably being efficiently recycled in the euphotic zone where silica levels are never depleted. The phytoplankton community structure observed by SEM is different to those reported previously, in which more traditional light microscopical techniques were used, with the consequence of missing the smaller phytoplankton. This study, regardless of its biogeographic location, highlights the potential problem of enumerating marine phytoplankton assemblages purely by light microscopy. An inability to determine the contribution made by these small phytoplankton can lead to an overestimation of the importance of large phytoplankton, and an underestimation of total productivity. r 2005 Elsevier Ltd. All rights reserved.

The development of DNA-chip technology has made it possible to analyse large numbers of probes in just one experiment. We show here the results of our first DNA-chip for the identification of phytoplankton. A set of previously published probes was chosen to be tested for their use on DNA-chips. Initially the probes were developled for other hybridisation-techniques, such as dot-blot-hybridisation or FISH (fluorescent in situ hybridisation). The probes target the 18S-DNA of phytoplankton at the level division or class. With the resulting DNA-chip, it was possible to identify specifically Prymnesiophyta, Chlorophyta and the Heterokont algal class Bolidophyceae. Our results indicate that DNA-chip-technology has great potential to serve as a useful tool for the phytoplankton analysis.

The diversity and abundance of the Bolidophyceae (Heterokonta), a newly described picoplanktonic algal class which is a sister group to the diatoms, was assessed in the equatorial Pacific Ocean and in the Mediterranean Sea by culture isolation, molecular biology techniques, and pigment analyses. Eight strains of Bolidophyceae were isolated in culture from different mesotrophic and oligotrophic areas. The corresponding small subunit (SSU) rRNA gene sequences allowed us to design two probes specific for the Bolidophyceae. These probes have been used in natural samples (i) to selectively amplify and detect Bolidophyceae sequences and (ii) to quantify the relative abundance of Bolidophyceae within the picoeukaryote community. Sequences available to date indicate that the class Bolidophyceae comprises at least three different clades, two corresponding to the previously described species Bolidomonas pacifica and Bolidomonas mediterranea and the third one corresponding to a subspecies of B. pacifica . Amplification of the SSU rRNA gene from natural samples with universal primers and hybridization using a Bolidomonas -specific probe followed by a eukaryote-specific probe allowed us to estimate the contribution of the Bolidophyceae to the eukaryotic DNA in both Pacific and Mediterranean waters to be lower than 1%. Similarly, high-performance liquid chromatography analyses of fucoxanthin, the major carotenoid present in Bolidophyceae, indicated that less than 4% of the total chlorophyll a in the picoplanktonic fraction in the equatorial Pacific was due to Bolidophyceae. Consequently, although strains of Bolidophyceae have been isolated from samples collected at several stations, this new class seems to have been a minor component of the natural picoeukaryotic populations in the ecosystems investigated, at least during the periods sampled.

Kleptoplastidy is the retention of plastids obtained from ingested algal prey, which may remain temporarily functional and be used for photosynthesis by the predator. We showed that the marine dinoflagellate Dinophysis mitra has great kleptoplastid diversity. We obtained 308 plastid rbc L sequences by gene cloning from 14 D. mitra cells and 102 operational taxonomic units (OTUs). Most sequences were new in the genetic database and positioned within Haptophyceae (227 sequences [73.7%], 80 OTUs [78.4%]), particularly within the genus Chrysochromulina . Others were closely related to Prasinophyceae (16 sequences [5.2%], 5 OTUs [4.9%]), Dictyochophyceae (14 sequences [4.5%], 5 OTUs [4.9%]), Pelagophyceae (14 sequences [4.5%], 1 OTU [1.0%]), Bolidophyceae (3 sequences [1.0%], 1 OTU [1.0%]), and Bacillariophyceae (1 sequence [0.3%], 1 OTU [1.0%]); however, 33 sequences (10.8%) as 9 OTUs (8.8%) were not closely clustered with any particular group. Only six sequences were identical to those of Chrysochromulina simplex , Chrysochromulina hirta , Chrysochromulina sp. TKB8936, Micromonas pusilla NEPCC29, Micromonas pusilla CCMP491, and an unidentified diatom. Thus, we detected >100 different plastid sequences from 14 D. mitra cells, strongly suggesting kleptoplastidy and the need for mixotrophic prey such as Laboea , Tontonia , and Strombidium -like ciliates, which retain numerous symbiotic plastids from different origins, for propagation and plastid sequestration.

Molecular data had consistently recovered monophyletic classes for the heterokont algae, however, the relationships among the classes had remained only partially resolved. Furthermore, earlier studies did not include representatives from all taxonomic classes. We used a five-gene (nuclear encoded SSU rRNA; plastid encoded rbcL, psaA, psbA, psbC) analysis with a subset of 89 taxa representing all 16 heterokont classes to infer a phylogenetic tree. There were three major clades. The Aurearenophyceae, Chrysomerophyceae, Phaeophyceae, Phaeothamniophyceae, Raphidophyceae, Schizocladiophyceae and Xanthophyceae formed the SI clade. The Chrysophyceae, Eustigmatophyceae, Pinguiophyceae, Synchromophyceae and Synurophyceae formed the SII clade. The Bacillariophyceae, Bolidophyceae, Dictyochophyceae and Pelagophyceae formed the SIII clade. These three clades were also found in a ten-gene analysis. The approximately unbiased test rejected alternative hypotheses that forced each class into either of the other two clades. Morphological and biochemical data were not available for all 89 taxa, however, existing data were consistent with the molecular phylogenetic tree, especially for the SIII clade.

International audience; A new algal class, the Bolidophyceae (Heterokonta), is described from one genus, Bolidomonas, gen, nov., and two species, Bolidomonas pacifica, sp, nov and Bolidomonas mediterranea, sp, nov., isolated from the equatorial Pacific Ocean and the Mediterranean Sea, respectively. Both species are approximately 1.2 mu m in diameter and have two unequal flagella; the longer flagellum bears tubular hairs, whereas the shorter is smooth. The flagellar basal apparatus is restricted to two basal bodies, and there is no transitional helix. Cells are naked, devoid of walls or siliceous structures. The internal cellular organization is simple with a single plastid containing a ring genophore and a girdle lamella, one mitochondrion with tubular cristae, and one Golgi apparatus close to the basal bodies. The Mediterranean and the Pacific species differ in the insertion angle between their flagella and their pattern of swimming, these differences possibly being linked to each other. Analyses of the SSU rDNA gene place the two strains as a sister group to the diatoms, Moreover, pigment analyses confirm this position, as fucoxanthin is found as the major carotenoid in both lineages. These data strongly suggest that the ancestral heterokont that gave rise to the diatom lineage was probably a biflagellated unicell.

A new order, Parmales, in the Chrysophyceae has cells with siliceous walls made up of round, triradiate and sometimes oblong plates all fitting edge to edge. In the new family, Octolaminaceae, cell walls have eight plates. Cell walls in the new genus Tetraparma have four round plates and four triradiate plates. Cell walls in the new genus Triparma have three round plates of equal size, one larger round plate, one triradiate plate and three oblong plates. In the new family, Pentalaminaceae, cell walls have three round and two triradiate plates. A total of seven new species and four subspecies are described from subarctic Pacific and Antarctic waters.

Photosynthetic picoeukaryotes (phytoplankton cells with a diameter smaller than 2 to 3 mum) contribute significantly to both biomass and primary production in the oligotrophic open ocean and coastal waters, at certain times of the year. The identification of these organisms is difficult because of their small size and simple morphology, therefore hindering detailed ecological studies of their distribution and role, In this paper, we demonstrate the use of oligonucleotide probes specific to algal classes or to lower order taxa in combination with fluorescent in situ hybridization and tyramide signal amplification (FISH-TSA) to determine eukaryotic picophytoplankton diversity, Target cells were detected and enumerated using epifluorescence microscopy. The sensitivity of the technique and the specificity of the probes were tested on pure and mixed picoplanktonic strains, as well as on natural samples from the English Channel. In these samples, the community was dominated by cells belonging to the division Chlorophyta. Haptophyta, Bolidophyceae and Pelagophyceae were also detected at low abundance. The FISH-TSA method is readily applicable to the study of picoplankton diversity in natural communities.