Aquatic ecosystems worldwide have been negatively affected by eutrophication, many of them driven... more Aquatic ecosystems worldwide have been negatively affected by eutrophication, many of them driven by increasing nutrient inputs from untreated domestic sewage and industrial and agricultural wastewater. During their life cycle, Alexandrium minutum and Scrippsiella donghaienis can produce resistant and revivable cysts that can accumulate in the sediments of the coastal marine environment for hundreds of years. As a working hypothesis, we presumed that these two genera have preserved their adaptation to such ecosystem changes in the form of cysts in the old sediments. From revivified cysts, some cultures of toxic and non-toxic dinoflagellates (A. minutum and S. donghaienis) were analyzed by a untargeted metabolomics approach by LC-HRMS to study the possible adaptive responses of phytoplankton to these modifications of coastal ecosystems. Strains of S. donghaienis were obtained from sediments isotopically dated to 1986 (ancient) and 2006 (modern) while those of A. minutum dated from 19...
Aquatic ecosystems worldwide have been negatively affected by eutrophication, many of them driven... more Aquatic ecosystems worldwide have been negatively affected by eutrophication, many of them driven by increasing nutrient inputs from untreated domestic sewage and industrial and agricultural wastewater. During their life cycle, Alexandrium minutum and Scrippsiella donghaienis can produce resistant and revivable cysts that can accumulate in the sediments of the coastal marine environment for hundreds of years. As a working hypothesis, we presumed that these two genera have preserved their adaptation to such ecosystem changes in the form of cysts in the old sediments. From revivified cysts, some cultures of toxic and non-toxic dinoflagellates (A. minutum and S. donghaienis) were analyzed by a metabolomic approach to study the possible adaptive responses of phytoplankton to these modifications of coastal ecosystems. Strains of Scrippsiella donghaienis were obtained from sediments isotopically dated to 1986 (ancient) and 2006 (modern) while those of A. minutum dated from 1996 (ancient) ...
SummaryIn a future scenario of increasing temperatures in North‐Atlantic waters, the risk associa... more SummaryIn a future scenario of increasing temperatures in North‐Atlantic waters, the risk associated with the expansion of the harmful, benthic dinoflagellateOstreopsiscf.siamensishas to be evaluated and monitored. Microscopy observations and spatio‐temporal surveys of environmental DNA (eDNA) were associated with Lagrangian particle dispersal simulations to: (i) establish the current colonization of the species in the Bay of Biscay, (ii) assess the spatial connectivity among sampling zones that explain this distribution, and (iii) identify the sentinel zones to monitor future expansion. Throughout a sampling campaign carried out in August to September 2018, microscope analysis showed that the species develops in the south‐east of the bay where optimal temperatures foster blooms. Quantitative PCR analyses revealed its presence across almost the whole bay to the western English Channel. An eDNA time‐series collected on plastic samplers showed that the species occurs in the bay from A...
Within the framework of research aimed at using genetic methods to evaluate harmful species distr... more Within the framework of research aimed at using genetic methods to evaluate harmful species distribution and their impact on coastal ecosystems, a portion of the ITS1rDNA of Alexandrium minutum was amplified by real-time PCR from DNA extracts of superficial (1-3 cm) sediments of 30 subtidal and intertidal stations of the Bay of Brest (Brittany, France), during the winters of 2013 and 2015. Cell germinations and rDNA amplifications of A. minutum were obtained for sediments of all sampled stations, demonstrating that the whole bay is currently contaminated by this toxic species. Coherent estimations of ITS1rDNA copy numbers were obtained for the two sampl ing cruises, supporting the hypothesis of regular accumulation of A. minutum resting stages in the southeastern , more confined embayments of the study area, where fine-muddy sediments are also more abundant. Higher ITS1rDNA copy numbers were detected in sediments of areas where blooms have been seasonally detected since 2012. This result suggests that specific genetic material estimations i n superficial sediments of the bay may be a proxy of the cyst banks of A. minutum. The simulation of particle trajectory analyses by a Lagrangian physical model showed that blooms occurring in the southeastern part of the bay are disconnected from those of the northeastern zone. The heterogeneous distribution of A. minutum inferred from both water and sediment suggests the existence of potential barriers for the dispersal of this species in the Bay of Brest and encourages finer analyses at the population level for this species within semi-enclosed coastal ecosystems.
s fueron Skeletonema japonicum y esporas de Chaetoceros Diplopsalis Scrippsiella Woloszynskia y l... more s fueron Skeletonema japonicum y esporas de Chaetoceros Diplopsalis Scrippsiella Woloszynskia y las especies Protoperidinium avellanum y P. leonis S. japonicum y de varias especies de Chaetoceros Stauroneis legleri, Pseudostaurosira trainorii Pseudostaurosira Pseudostaurosira Navicula pseudoreinhardtii Woloszynskia afectaron la sobrevivencia de las esporas de resistencia. PALABRAS CLAVE s Skeletonema japonicum and Chaetoceros Diplopsalis Scrippsiella Woloszynskia and the species Protoperidinium avellanum and P. leonis S. japonicum and several of the Chaetoceros growth were Stauroneis legleri Pseudostaurosira trainorii Pseudostaurosira Pseudostaurosira Navicula pseudoreinhardtii Woloszynskia sp. also germinated and grew abundantly in the culture.
The distribution of summer phytoplankton across the Straits of Magellan (SOM) was studied with th... more The distribution of summer phytoplankton across the Straits of Magellan (SOM) was studied with the aims of tracing diVerences among the distinct subregions of the area and contributing to the knowledge of its biodiversity. Samples collected at 25 stations were observed and counted in light microscopy. Selected samples were observed with transmission electron microscopy. The main unifying feature of the phytoplankton in the SOM was the high abundance and numerical dominance of small-sized (<10 m) eukaryotic species, among which coccoid cells of <3 m size were predominant (56.2 § 30.6 of the total phytoplankton abundance). They mostly belonged to the prasinophyte Pycnococcus provasolii, which was abundant (0.8-6,834 cells £ 10 3 ml ¡1) at all stations with the exception of those in proximity to the Atlantic entrances, where it was not recorded. Small-sized (<3 and 3-5 m) diatoms (Minidiscus trioculatus, Lennoxia faveolata and other undetermined centric species) attained high densities (<3,757 cells 10 3 ml ¡1) especially at stations of the Patagonian sectors, whereas microplanktonic diatoms were only found at the two entrances of the Straits. DinoXagellates were constituted mainly by >10 m forms in the Andean subregion and <10 m naked species in the Patagonian subregion, contributing up to 75.9 and 41.8% of the total carbon in these two areas, respectively. In the Patagonian subregion, Xagellates mainly constituted by <5 m forms and by cryptomonads <10 m comprised up to 53.9% of the total biomass. Several species identiWed in this study have never been reported in other investigations in the SOM, while others, including Pycnococcus provasolii and Lennoxia faveolata, have rarely been recorded elsewhere. Overall, the summer phytoplankton of the Straits does not resemble that of any other region of the world's seas. Although some of the predominant species might have been overlooked elsewhere, their abundance and relative importance apparently constitute a distinctive feature of the SOM.
Abstract The unarmoured dinoflagellate assemblage of the Gulf of Naples has been investigated in ... more Abstract The unarmoured dinoflagellate assemblage of the Gulf of Naples has been investigated in the frame of a 1-year sampling of natural surface samples collected weekly at a coastal station c. 2 miles offshore. Twenty-six strains of unarmoured dinoflagellates were ...
The interrogation of genetic markers in environmental meta-barcoding studies is currently serious... more The interrogation of genetic markers in environmental meta-barcoding studies is currently seriously hindered by the lack of taxonomically curated reference data sets for the targeted genes. The Protist Ribosomal Reference database (PR 2 , http://ssurrna.org/) provides a unique access to eukaryotic small sub-unit (SSU) ribosomal RNA and DNA sequences, with curated taxonomy. The database mainly consists of nuclear-encoded protistan sequences. However, metazoans, land plants, macrosporic fungi and eukaryotic organelles (mitochondrion, plastid and others) are also included because they are useful for the analysis of hightroughput sequencing data sets. Introns and putative chimeric sequences have been also carefully checked. Taxonomic assignation of sequences consists of eight unique taxonomic fields. In total,
Symbiotic interactions between pelagic hosts and microalgae have received little attention, despi... more Symbiotic interactions between pelagic hosts and microalgae have received little attention, despite the fact that they are widespread in the photic layer of the world ocean where they play a fundamental role in the ecology of the planktonic ecosystem. Polycystine radiolarians (including the orders Spumellaria, Collodaria and Nassellaria) are planktonic heterotrophic protists that are widely distributed and often abundant in the ocean. Many polycystines host symbiotic microalgae within their cytoplasm, mostly thought to be the dinoflagellate Scrippsiella nutricula, a species originally described by Karl Brandt in the late nineteenth century as Zooxanthella nutricula. The free-living stage of this dinoflagellate has never been characterized in terms of morphology and thecal plate tabulation. We examined morphological characters and sequenced conservative ribosomal markers of clonal cultures of the free-living stage of symbiotic dinoflagellates isolated from radiolarian hosts from the three polycystine orders. In addition, we sequenced symbiont genes directly from several polycystine-symbiont holobiont specimens from different oceanic regions. Thecal plate arrangement of the free-living stage does not match that of Scrippsiella or related genera, and LSU and SSU rDNA-based molecular phylogenies place these symbionts in a distinct clade within the Peridiniales. Both phylogenetic analyses and the comparison of morphological features of culture strains with those reported for other closely related species support the erection of a new genus that we name Brandtodinium gen. nov. and the recombination of S. nutricula as B. nutriculum
... Vesuvius on the coast of the Gulf of Naples is one of the few active volcanoes in Europe. The... more ... Vesuvius on the coast of the Gulf of Naples is one of the few active volcanoes in Europe. The two gulfs of Naples and Salerno, separated by the Sorrento peninsula, are world famous for the high cliffs, sandy bays and the beautiful islands (Ischia, Procida and Capri). ...
Protoperidinium vorax sp. nov. is a small heterotrophic dinoflagellate with a plate formula of Po... more Protoperidinium vorax sp. nov. is a small heterotrophic dinoflagellate with a plate formula of Po, X, 4 0 , 3a, 7 00 , 3C, 5S, 5 000 , 0p, 2 0000. P. vorax has an ortho-hexa thecal plate arrangement. Its peculiar features are the presence of only three cingular plates and the marked extension of the second intercalary plate (2a), which abuts the second precingular plate (2 00). TEM sections revealed the presence of a large sac pusule, several convoluted vesicular structures and electron-dense accumulation bodies scattered in the cell periphery. These accumulation bodies probably represent the Periodic Acid-Schiff (PAS) bodies, which fluoresce yellow-green under blue light excitation. P. vorax is a pallium feeder and was observed feeding on diatoms of different sizes. When fed with the chain-forming diatom Skeletonema pseudocostatum under non-limiting food concentrations, doubling rates up to 1.28 divisions d À1 were recorded. Ingestion rates of 35.95 cells dinoflagellate À1 h À1 and clearance rates of 18.34 ml dinoflagellate À1 h À1 were reached, the highest ever recorded for a small-sized dinoflagellate. These data support the hypothesis that small heterotrophic species might contribute to diatom bloom decay.
The section of the Liguro-Provencal basin north of the Balearic Islands is one of the most produc... more The section of the Liguro-Provencal basin north of the Balearic Islands is one of the most productive sites in the whole Mediterranean Sea, with intense phytoplankton bloom lasting about 2 months in late winter-early spring. The phytoplankton species composition of the area was investigated using light and electron microscopy to analyze bottle and net samples collected at several stations in spring 2000 and 2003. Serial dilution cultures established from bottle samples were also examined. A total of 168 phytoplankton taxa was identified, consisting of 73 Coscinodiscophyceae, 47 Dinophyceae, 25 Coccolithophyceae and 4 Prymnesiophyceae, 5 Prasinophyceae, 3 Chrysophyceae, 2 Cryptophyceae, 2 Dictyochophyceae, 1 Euglenophyceae, 1 Pelagophyceae, 1 Choanoflagellidea, 1 Filosea and 3 incertae sedis. We also provided a brief taxonomic description and original micrographs for 25 of the smallest and/or less known species identified in the study area, which may go undetected during routine microscopical analysis of fixed samples. Among these, 10 species were recorded for the first time in the Mediterranean Sea, confirming the need of detailed studies to reveal the biodiversity and biogeography of Mediterranean phytoplankton.
During the MALINA cruise (summer 2009), an extensive effort was undertaken to isolate phytoplankt... more During the MALINA cruise (summer 2009), an extensive effort was undertaken to isolate phytoplankton strains from the northeast (NE) Pacific Ocean, the Bering Strait, the Chukchi Sea, and the Beaufort Sea. In order to characterise the main photosynthetic microorganisms occurring in the Arctic during the summer season, strains were isolated by flow cytometry sorting (FCS) and single cell pipetting before or after phytoplankton enrichment of seawater samples. Strains were isolated both onboard and back in the laboratory and cultured at 4 • C under light/dark conditions. Overall, we isolated and characterised by light microscopy and 18 S rRNA gene sequencing 104 strains of photosynthetic flagellates which grouped into 21 genotypes (defined by 99.5 % 18 S rRNA gene sequence similarity), mainly affiliated to Chlorophyta and Heterokontophyta. The taxon most frequently isolated was an Arctic ecotype of the green algal genus Micromonas (Arctic Micromonas), which was nearly the only phytoplankter recovered within the picoplankton (< 2 µm) size range. Strains of Arctic Micromonas as well as other strains from the same class (Mamiellophyceae) were identified in further detail by sequencing the internal transcribed spacer (ITS) region of the rRNA operon. The MALINA Micromonas strains share identical 18 S rRNA and ITS sequences suggesting high genetic homogeneity within Arctic Micromonas. Three other Mamiellophyceae strains likely belong to a new genus. Other green algae from the genera Nephroselmis, Chlamydomonas, and Pyramimonas were also isolated, whereas Heterokontophyta included some unidentified Pelagophyceae, Dictyochophyceae (Pedinellales), and Chrysophyceae (Dinobryon faculiferum). Moreover, we isolated some Cryptophyceae (Rhodomonas sp.) as well as a few Prymnesiophyceae and dinoflagellates. We identified the dinoflagellate Woloszynskia cincta by scanning electron microscopy (SEM) and 28 S rRNA gene sequencing. Our morphological analyses show that this species possess the diagnostic features of the genus Biecheleria, and the 28 S rRNA gene topology corroborates this affiliation. We thus propose the transfer of W. cincta to the genus Biecheleria and its recombination as Biecheleria cincta.
Vampire amoebae (vampyrellids) are predators of algae, fungi, protozoa and small metazoans known ... more Vampire amoebae (vampyrellids) are predators of algae, fungi, protozoa and small metazoans known primarily from soils and in freshwater habitats. They are among the very few heterotrophic naked, filose and reticulose protists that have received some attention from a morphological and ecological point of view over the last few decades, because of the peculiar mode of feeding of known species. Yet, the true extent of their biodiversity remains largely unknown. Here we use a complementary approach of culturing and sequence database mining to address this issue, focusing our efforts on marine environments, where vampyrellids are very poorly known. We present 10 new vampyrellid isolates, 8 from marine or brackish sediments, and 2 from soil or freshwater sediment. Two of the former correspond to the genera Thalassomyxa Grell and Penardia Cash for which sequence data were previously unavailable. Small-subunit ribosomal DNA analysis confirms they are all related to previously sequenced vampyrellids. An exhaustive screening of the NCBI GenBank database and of 454 sequence data generated by the European BioMarKs consortium revealed hundreds of distinct environmental vampyrellid sequences. We show that vampyrellids are much more diverse than previously thought, especially in marine habitats. Our new isolates, which cover almost the full phylogenetic range of vampyrellid sequences revealed in this study, offer a rare opportunity to integrate data from environmental DNA surveys with phenotypic information. However, the very large genetic diversity we highlight within vampyrellids (especially in marine sediments and soils) contrasts with the paradoxically low morphological distinctiveness we observed across our isolates.
Aquatic ecosystems worldwide have been negatively affected by eutrophication, many of them driven... more Aquatic ecosystems worldwide have been negatively affected by eutrophication, many of them driven by increasing nutrient inputs from untreated domestic sewage and industrial and agricultural wastewater. During their life cycle, Alexandrium minutum and Scrippsiella donghaienis can produce resistant and revivable cysts that can accumulate in the sediments of the coastal marine environment for hundreds of years. As a working hypothesis, we presumed that these two genera have preserved their adaptation to such ecosystem changes in the form of cysts in the old sediments. From revivified cysts, some cultures of toxic and non-toxic dinoflagellates (A. minutum and S. donghaienis) were analyzed by a untargeted metabolomics approach by LC-HRMS to study the possible adaptive responses of phytoplankton to these modifications of coastal ecosystems. Strains of S. donghaienis were obtained from sediments isotopically dated to 1986 (ancient) and 2006 (modern) while those of A. minutum dated from 19...
Aquatic ecosystems worldwide have been negatively affected by eutrophication, many of them driven... more Aquatic ecosystems worldwide have been negatively affected by eutrophication, many of them driven by increasing nutrient inputs from untreated domestic sewage and industrial and agricultural wastewater. During their life cycle, Alexandrium minutum and Scrippsiella donghaienis can produce resistant and revivable cysts that can accumulate in the sediments of the coastal marine environment for hundreds of years. As a working hypothesis, we presumed that these two genera have preserved their adaptation to such ecosystem changes in the form of cysts in the old sediments. From revivified cysts, some cultures of toxic and non-toxic dinoflagellates (A. minutum and S. donghaienis) were analyzed by a metabolomic approach to study the possible adaptive responses of phytoplankton to these modifications of coastal ecosystems. Strains of Scrippsiella donghaienis were obtained from sediments isotopically dated to 1986 (ancient) and 2006 (modern) while those of A. minutum dated from 1996 (ancient) ...
SummaryIn a future scenario of increasing temperatures in North‐Atlantic waters, the risk associa... more SummaryIn a future scenario of increasing temperatures in North‐Atlantic waters, the risk associated with the expansion of the harmful, benthic dinoflagellateOstreopsiscf.siamensishas to be evaluated and monitored. Microscopy observations and spatio‐temporal surveys of environmental DNA (eDNA) were associated with Lagrangian particle dispersal simulations to: (i) establish the current colonization of the species in the Bay of Biscay, (ii) assess the spatial connectivity among sampling zones that explain this distribution, and (iii) identify the sentinel zones to monitor future expansion. Throughout a sampling campaign carried out in August to September 2018, microscope analysis showed that the species develops in the south‐east of the bay where optimal temperatures foster blooms. Quantitative PCR analyses revealed its presence across almost the whole bay to the western English Channel. An eDNA time‐series collected on plastic samplers showed that the species occurs in the bay from A...
Within the framework of research aimed at using genetic methods to evaluate harmful species distr... more Within the framework of research aimed at using genetic methods to evaluate harmful species distribution and their impact on coastal ecosystems, a portion of the ITS1rDNA of Alexandrium minutum was amplified by real-time PCR from DNA extracts of superficial (1-3 cm) sediments of 30 subtidal and intertidal stations of the Bay of Brest (Brittany, France), during the winters of 2013 and 2015. Cell germinations and rDNA amplifications of A. minutum were obtained for sediments of all sampled stations, demonstrating that the whole bay is currently contaminated by this toxic species. Coherent estimations of ITS1rDNA copy numbers were obtained for the two sampl ing cruises, supporting the hypothesis of regular accumulation of A. minutum resting stages in the southeastern , more confined embayments of the study area, where fine-muddy sediments are also more abundant. Higher ITS1rDNA copy numbers were detected in sediments of areas where blooms have been seasonally detected since 2012. This result suggests that specific genetic material estimations i n superficial sediments of the bay may be a proxy of the cyst banks of A. minutum. The simulation of particle trajectory analyses by a Lagrangian physical model showed that blooms occurring in the southeastern part of the bay are disconnected from those of the northeastern zone. The heterogeneous distribution of A. minutum inferred from both water and sediment suggests the existence of potential barriers for the dispersal of this species in the Bay of Brest and encourages finer analyses at the population level for this species within semi-enclosed coastal ecosystems.
s fueron Skeletonema japonicum y esporas de Chaetoceros Diplopsalis Scrippsiella Woloszynskia y l... more s fueron Skeletonema japonicum y esporas de Chaetoceros Diplopsalis Scrippsiella Woloszynskia y las especies Protoperidinium avellanum y P. leonis S. japonicum y de varias especies de Chaetoceros Stauroneis legleri, Pseudostaurosira trainorii Pseudostaurosira Pseudostaurosira Navicula pseudoreinhardtii Woloszynskia afectaron la sobrevivencia de las esporas de resistencia. PALABRAS CLAVE s Skeletonema japonicum and Chaetoceros Diplopsalis Scrippsiella Woloszynskia and the species Protoperidinium avellanum and P. leonis S. japonicum and several of the Chaetoceros growth were Stauroneis legleri Pseudostaurosira trainorii Pseudostaurosira Pseudostaurosira Navicula pseudoreinhardtii Woloszynskia sp. also germinated and grew abundantly in the culture.
The distribution of summer phytoplankton across the Straits of Magellan (SOM) was studied with th... more The distribution of summer phytoplankton across the Straits of Magellan (SOM) was studied with the aims of tracing diVerences among the distinct subregions of the area and contributing to the knowledge of its biodiversity. Samples collected at 25 stations were observed and counted in light microscopy. Selected samples were observed with transmission electron microscopy. The main unifying feature of the phytoplankton in the SOM was the high abundance and numerical dominance of small-sized (<10 m) eukaryotic species, among which coccoid cells of <3 m size were predominant (56.2 § 30.6 of the total phytoplankton abundance). They mostly belonged to the prasinophyte Pycnococcus provasolii, which was abundant (0.8-6,834 cells £ 10 3 ml ¡1) at all stations with the exception of those in proximity to the Atlantic entrances, where it was not recorded. Small-sized (<3 and 3-5 m) diatoms (Minidiscus trioculatus, Lennoxia faveolata and other undetermined centric species) attained high densities (<3,757 cells 10 3 ml ¡1) especially at stations of the Patagonian sectors, whereas microplanktonic diatoms were only found at the two entrances of the Straits. DinoXagellates were constituted mainly by >10 m forms in the Andean subregion and <10 m naked species in the Patagonian subregion, contributing up to 75.9 and 41.8% of the total carbon in these two areas, respectively. In the Patagonian subregion, Xagellates mainly constituted by <5 m forms and by cryptomonads <10 m comprised up to 53.9% of the total biomass. Several species identiWed in this study have never been reported in other investigations in the SOM, while others, including Pycnococcus provasolii and Lennoxia faveolata, have rarely been recorded elsewhere. Overall, the summer phytoplankton of the Straits does not resemble that of any other region of the world's seas. Although some of the predominant species might have been overlooked elsewhere, their abundance and relative importance apparently constitute a distinctive feature of the SOM.
Abstract The unarmoured dinoflagellate assemblage of the Gulf of Naples has been investigated in ... more Abstract The unarmoured dinoflagellate assemblage of the Gulf of Naples has been investigated in the frame of a 1-year sampling of natural surface samples collected weekly at a coastal station c. 2 miles offshore. Twenty-six strains of unarmoured dinoflagellates were ...
The interrogation of genetic markers in environmental meta-barcoding studies is currently serious... more The interrogation of genetic markers in environmental meta-barcoding studies is currently seriously hindered by the lack of taxonomically curated reference data sets for the targeted genes. The Protist Ribosomal Reference database (PR 2 , http://ssurrna.org/) provides a unique access to eukaryotic small sub-unit (SSU) ribosomal RNA and DNA sequences, with curated taxonomy. The database mainly consists of nuclear-encoded protistan sequences. However, metazoans, land plants, macrosporic fungi and eukaryotic organelles (mitochondrion, plastid and others) are also included because they are useful for the analysis of hightroughput sequencing data sets. Introns and putative chimeric sequences have been also carefully checked. Taxonomic assignation of sequences consists of eight unique taxonomic fields. In total,
Symbiotic interactions between pelagic hosts and microalgae have received little attention, despi... more Symbiotic interactions between pelagic hosts and microalgae have received little attention, despite the fact that they are widespread in the photic layer of the world ocean where they play a fundamental role in the ecology of the planktonic ecosystem. Polycystine radiolarians (including the orders Spumellaria, Collodaria and Nassellaria) are planktonic heterotrophic protists that are widely distributed and often abundant in the ocean. Many polycystines host symbiotic microalgae within their cytoplasm, mostly thought to be the dinoflagellate Scrippsiella nutricula, a species originally described by Karl Brandt in the late nineteenth century as Zooxanthella nutricula. The free-living stage of this dinoflagellate has never been characterized in terms of morphology and thecal plate tabulation. We examined morphological characters and sequenced conservative ribosomal markers of clonal cultures of the free-living stage of symbiotic dinoflagellates isolated from radiolarian hosts from the three polycystine orders. In addition, we sequenced symbiont genes directly from several polycystine-symbiont holobiont specimens from different oceanic regions. Thecal plate arrangement of the free-living stage does not match that of Scrippsiella or related genera, and LSU and SSU rDNA-based molecular phylogenies place these symbionts in a distinct clade within the Peridiniales. Both phylogenetic analyses and the comparison of morphological features of culture strains with those reported for other closely related species support the erection of a new genus that we name Brandtodinium gen. nov. and the recombination of S. nutricula as B. nutriculum
... Vesuvius on the coast of the Gulf of Naples is one of the few active volcanoes in Europe. The... more ... Vesuvius on the coast of the Gulf of Naples is one of the few active volcanoes in Europe. The two gulfs of Naples and Salerno, separated by the Sorrento peninsula, are world famous for the high cliffs, sandy bays and the beautiful islands (Ischia, Procida and Capri). ...
Protoperidinium vorax sp. nov. is a small heterotrophic dinoflagellate with a plate formula of Po... more Protoperidinium vorax sp. nov. is a small heterotrophic dinoflagellate with a plate formula of Po, X, 4 0 , 3a, 7 00 , 3C, 5S, 5 000 , 0p, 2 0000. P. vorax has an ortho-hexa thecal plate arrangement. Its peculiar features are the presence of only three cingular plates and the marked extension of the second intercalary plate (2a), which abuts the second precingular plate (2 00). TEM sections revealed the presence of a large sac pusule, several convoluted vesicular structures and electron-dense accumulation bodies scattered in the cell periphery. These accumulation bodies probably represent the Periodic Acid-Schiff (PAS) bodies, which fluoresce yellow-green under blue light excitation. P. vorax is a pallium feeder and was observed feeding on diatoms of different sizes. When fed with the chain-forming diatom Skeletonema pseudocostatum under non-limiting food concentrations, doubling rates up to 1.28 divisions d À1 were recorded. Ingestion rates of 35.95 cells dinoflagellate À1 h À1 and clearance rates of 18.34 ml dinoflagellate À1 h À1 were reached, the highest ever recorded for a small-sized dinoflagellate. These data support the hypothesis that small heterotrophic species might contribute to diatom bloom decay.
The section of the Liguro-Provencal basin north of the Balearic Islands is one of the most produc... more The section of the Liguro-Provencal basin north of the Balearic Islands is one of the most productive sites in the whole Mediterranean Sea, with intense phytoplankton bloom lasting about 2 months in late winter-early spring. The phytoplankton species composition of the area was investigated using light and electron microscopy to analyze bottle and net samples collected at several stations in spring 2000 and 2003. Serial dilution cultures established from bottle samples were also examined. A total of 168 phytoplankton taxa was identified, consisting of 73 Coscinodiscophyceae, 47 Dinophyceae, 25 Coccolithophyceae and 4 Prymnesiophyceae, 5 Prasinophyceae, 3 Chrysophyceae, 2 Cryptophyceae, 2 Dictyochophyceae, 1 Euglenophyceae, 1 Pelagophyceae, 1 Choanoflagellidea, 1 Filosea and 3 incertae sedis. We also provided a brief taxonomic description and original micrographs for 25 of the smallest and/or less known species identified in the study area, which may go undetected during routine microscopical analysis of fixed samples. Among these, 10 species were recorded for the first time in the Mediterranean Sea, confirming the need of detailed studies to reveal the biodiversity and biogeography of Mediterranean phytoplankton.
During the MALINA cruise (summer 2009), an extensive effort was undertaken to isolate phytoplankt... more During the MALINA cruise (summer 2009), an extensive effort was undertaken to isolate phytoplankton strains from the northeast (NE) Pacific Ocean, the Bering Strait, the Chukchi Sea, and the Beaufort Sea. In order to characterise the main photosynthetic microorganisms occurring in the Arctic during the summer season, strains were isolated by flow cytometry sorting (FCS) and single cell pipetting before or after phytoplankton enrichment of seawater samples. Strains were isolated both onboard and back in the laboratory and cultured at 4 • C under light/dark conditions. Overall, we isolated and characterised by light microscopy and 18 S rRNA gene sequencing 104 strains of photosynthetic flagellates which grouped into 21 genotypes (defined by 99.5 % 18 S rRNA gene sequence similarity), mainly affiliated to Chlorophyta and Heterokontophyta. The taxon most frequently isolated was an Arctic ecotype of the green algal genus Micromonas (Arctic Micromonas), which was nearly the only phytoplankter recovered within the picoplankton (< 2 µm) size range. Strains of Arctic Micromonas as well as other strains from the same class (Mamiellophyceae) were identified in further detail by sequencing the internal transcribed spacer (ITS) region of the rRNA operon. The MALINA Micromonas strains share identical 18 S rRNA and ITS sequences suggesting high genetic homogeneity within Arctic Micromonas. Three other Mamiellophyceae strains likely belong to a new genus. Other green algae from the genera Nephroselmis, Chlamydomonas, and Pyramimonas were also isolated, whereas Heterokontophyta included some unidentified Pelagophyceae, Dictyochophyceae (Pedinellales), and Chrysophyceae (Dinobryon faculiferum). Moreover, we isolated some Cryptophyceae (Rhodomonas sp.) as well as a few Prymnesiophyceae and dinoflagellates. We identified the dinoflagellate Woloszynskia cincta by scanning electron microscopy (SEM) and 28 S rRNA gene sequencing. Our morphological analyses show that this species possess the diagnostic features of the genus Biecheleria, and the 28 S rRNA gene topology corroborates this affiliation. We thus propose the transfer of W. cincta to the genus Biecheleria and its recombination as Biecheleria cincta.
Vampire amoebae (vampyrellids) are predators of algae, fungi, protozoa and small metazoans known ... more Vampire amoebae (vampyrellids) are predators of algae, fungi, protozoa and small metazoans known primarily from soils and in freshwater habitats. They are among the very few heterotrophic naked, filose and reticulose protists that have received some attention from a morphological and ecological point of view over the last few decades, because of the peculiar mode of feeding of known species. Yet, the true extent of their biodiversity remains largely unknown. Here we use a complementary approach of culturing and sequence database mining to address this issue, focusing our efforts on marine environments, where vampyrellids are very poorly known. We present 10 new vampyrellid isolates, 8 from marine or brackish sediments, and 2 from soil or freshwater sediment. Two of the former correspond to the genera Thalassomyxa Grell and Penardia Cash for which sequence data were previously unavailable. Small-subunit ribosomal DNA analysis confirms they are all related to previously sequenced vampyrellids. An exhaustive screening of the NCBI GenBank database and of 454 sequence data generated by the European BioMarKs consortium revealed hundreds of distinct environmental vampyrellid sequences. We show that vampyrellids are much more diverse than previously thought, especially in marine habitats. Our new isolates, which cover almost the full phylogenetic range of vampyrellid sequences revealed in this study, offer a rare opportunity to integrate data from environmental DNA surveys with phenotypic information. However, the very large genetic diversity we highlight within vampyrellids (especially in marine sediments and soils) contrasts with the paradoxically low morphological distinctiveness we observed across our isolates.
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Papers by R. Siano