| 1. |
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| 2. |
- Adl, Sina M., et al.
(författare)
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Revisions to the Classification, Nomenclature, and Diversity of Eukaryotes
- 2019
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Ingår i: Journal of Eukaryotic Microbiology. - : WILEY. - 1066-5234 .- 1550-7408. ; 66:1, s. 4-119
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Tidskriftsartikel (refereegranskat)abstract
- This revision of the classification of eukaryotes follows that of Adl et al., 2012 [J. Euk. Microbiol. 59(5)] and retains an emphasis on protists. Changes since have improved the resolution of many nodes in phylogenetic analyses. For some clades even families are being clearly resolved. As we had predicted, environmental sampling in the intervening years has massively increased the genetic information at hand. Consequently, we have discovered novel clades, exciting new genera and uncovered a massive species level diversity beyond the morphological species descriptions. Several clades known from environmental samples only have now found their home. Sampling soils, deeper marine waters and the deep sea will continue to fill us with surprises. The main changes in this revision are the confirmation that eukaryotes form at least two domains, the loss of monophyly in the Excavata, robust support for the Haptista and Cryptista. We provide suggested primer sets for DNA sequences from environmental samples that are effective for each clade. We have provided a guide to trophic functional guilds in an appendix, to facilitate the interpretation of environmental samples, and a standardized taxonomic guide for East Asian users.
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| 3. |
- Alfjorden, Anders, et al.
(författare)
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Identification of a new gregarine parasite associated with mass mortality events of freshwater pearl mussels (Margaritifera margaritifera) in Sweden
- 2024
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Ingår i: JOURNAL OF EUKARYOTIC MICROBIOLOGY. - 1066-5234 .- 1550-7408.
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Tidskriftsartikel (refereegranskat)abstract
- Freshwater bivalves play key ecological roles in lakes and rivers, largely contributing to healthy ecosystems. The freshwater pearl mussel, Margaritifera margaritifera, is found in Europe and on the East coast of North America. Once common in oxygenated streams, M. margaritifera is rapidly declining and consequently assessed as a threatened species worldwide. Deterioration of water quality has been considered the main factor for the mass mortality events affecting this species. Yet, the role of parasitic infections has not been investigated. Here, we report the discovery of three novel protist lineages found in Swedish populations of M. margaritifera belonging to one of the terrestrial groups of gregarines (Eugregarinorida, Apicomplexa). These lineages are closely related-but clearly separated-from the tadpole parasite Nematopsis temporariae. In one lineage, which is specifically associated with mortality events of M. margaritifera, we found cysts containing single vermiform zoites in the gills and other organs of diseased individuals using microscopy and in situ hybridization. This represents the first report of a parasitic infection in M. margaritifera that may be linked to the decline of this mussel species. We propose a tentative life cycle with the distribution of different developmental stages and potential exit from the host into the environment.
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| 4. |
- Billker, Oliver, et al.
(författare)
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Azadirachtin disrupts formation of organised microtubule arrays during microgametogenesis of Plasmodium berghei
- 2002
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Ingår i: Journal of Eukaryotic Microbiology. - : Wiley. - 1066-5234 .- 1550-7408. ; 49:6, s. 489-497
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Tidskriftsartikel (refereegranskat)abstract
- Transmission of malaria parasites from vertebrate blood to the mosquito vector depends critically on the differentiation of the gametocytes into gametes. This occurs in response to environmental stimuli encountered by the parasite in the mosquito bloodmeal. Male gametogenesis involves three rounds of DNA replication and endomitosis, and the assembly de novo of 8 motile axonemes. Azadirachtin, a plant limnoid and insecticide with an unkown mode of action, specifically inhibits the release of motile gametes from activated microgametocytes but does not inhibit growth and replication of a sexual blood stages. We have combined confocal laser scanning microscopy and transmission electron microscopy to examine the effect of azadirachtin on the complex reorganisation of the microtubule cytoskeleton during gametogenesis in Plasmodium berghei. Neither the replication of the genome nor the ability of tubulin monomers to assemble into microtubules upon gametocyte activation were prevented by azadirachtin. However, the drug interfered with the formation of mitotic spindles and with the assembly of microtubules into typical axonemes. Our observations suggest that azadarachtin specifically disrupts the patterning of microtubules into more complex structures, such as mitotic spindles and axonemes.
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| 5. |
- Brinkmann, Inda, et al.
(författare)
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Through the eDNA looking glass: Responses of fjord benthic foraminiferal communities to contrasting environmental conditions
- 2023
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Ingår i: Journal of Eukaryotic Microbiology. - : Wiley. - 1066-5234 .- 1550-7408. ; 70:4
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Tidskriftsartikel (refereegranskat)abstract
- The health of coastal marine environments is severely declining with global changes. Proxies, such as those based on microeukaryote communities, can record biodiversity and ecosystem responses. However, conventional studies rely on microscopic observations of limited taxonomic range and size fraction, missing putatively ecologically informative community components. Here, we tested molecular tools to survey foraminiferal biodiversity in a fjord system (Sweden) on spatial and temporal scales: Alpha and beta diversity responses to natural and anthropogenic environmental trends were assessed and variability of foraminiferal environmental DNA (eDNA) compared to morphology-based data. The identification of eDNA-obtained taxonomic units was aided by single-cell barcoding. Our study revealed wide diversity, including typical morphospecies recognized in the fjords, and so-far unrecognized taxa. DNA extraction method impacted community composition outputs significantly. DNA extractions of 10 g sediment more reliably represented present diversity than of 0.5-g samples and, thus, are preferred for environmental assessments in this region. Alpha- and beta diversity of 10-g extracts correlated with bottom-water salinity similar to morpho-assemblage diversity changes. Sub-annual environmental variability resolved only partially, indicating damped sensitivity of foraminiferal communities on short timescales using established metabarcoding techniques. Systematically addressing the current limitations of morphology-based and metabarcoding studies may strongly improve future biodiversity and environmental assessments.
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| 6. |
- Carr, Martin, et al.
(författare)
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Conserved Meiotic Genes Point to Sex in the Choanoflagellates
- 2010
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Ingår i: Journal of Eukaryotic Microbiology. - : Wiley. - 1066-5234 .- 1550-7408. ; 57:1, s. 56-62
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Tidskriftsartikel (refereegranskat)abstract
- The choanoflagellates are a widespread group of heterotrophic aquatic nanoflagellates, which have recently been confirmed as the sister-group to Metazoa. Asexual reproduction is the only mode of cell division that has been observed within the group; at present the range of reproductive modes, as well as the ploidy level, within choanoflagellates are unknown. The recent discovery of long terminal repeat retrotransposons within the genome of Monosiga brevicollis suggests that this species also has sexual stages in its life cycle because asexual organisms cannot tolerate retrotransposons due to the rapid accumulation of deleterious mutations caused by their transposition. We screened the M. brevicollis genome for known eukaryotic meiotic genes, using a recently established "meiosis detection toolkit" of 19 genes. Eighteen of these genes were identified, none of which appears to be a pseudogene. Four of the genes were also identified in expressed sequence tag data from the distantly related Monosiga ovata. The presence of these meiosis-specific genes provides evidence for meiosis, and by implication sex, within this important group of protists.
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| 7. |
- Chang, Yue, et al.
(författare)
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Cd-Metallothioneins in Three Additional Tetrahymena Species : Intragenic Repeat Patterns and Induction by Metal Ions
- 2014
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Ingår i: Journal of Eukaryotic Microbiology. - : Wiley. - 1066-5234 .- 1550-7408. ; 61:4, s. 333-342
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Tidskriftsartikel (refereegranskat)abstract
- Ciliate metallothioneins (MTs) possess many unique features compared to the "classic" MTs in other organisms, but they have only been studied in a small number of species. In this study, we investigated cDNAs encoding subfamily 7a metallothioneins (CdMTs) in three Tetrahymena species (T. hegewischi, T. malaccensis, and T. mobilis). Four CdMT genes (ThegMT1, ThegMT2, TmalMT1, and TmobMT1) were cloned and characterized. They share high sequence similarity to previously identified subfamily 7a MT members. Tetrahymena CdMTs exhibit a remarkably regular intragenic repeat homology. The CdMT sequences were divided into two main types of modules, which had been previously described, and which we name "A" and "B". ThegMT2 was identified as the first MT isoform solely composed of module "B". A phylogenetic analysis of individual modules of every characterized Tetrahymena CdMT rigorously documents the conclusion that modules are important units of CdMT evolution, which have undergone frequent and rapid gain/loss and shuffling. The transcriptional activity of the four newly identified genes was measured under different heavy metal exposure (Cd, Cu, Zn, Pb) using real-time quantitative PCR. The results showed that these genes were differentially induced after short (1 h) or long (24 h) metal exposure. The evolutionary diversity of Tetrahymena CdMTs is further discussed with regard to their induction by metal ions.
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| 8. |
- Gran-Stadniczeñko, Sandra, et al.
(författare)
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Haptophyte diversity and vertical distribution explored by 18S and 28S ribosomal RNA gene metabarcoding and scanning electron microscopy
- 2017
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Ingår i: Journal of Eukaryotic Microbiology. - : Wiley. - 1066-5234 .- 1550-7408. ; 64:4, s. 514-532
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Tidskriftsartikel (refereegranskat)abstract
- Haptophyta encompasses more than 300 species of mostly marine pico- and nanoplanktonic flagellates. Our aims were to investigate the Oslofjorden haptophyte diversity and vertical distribution by metabarcoding, and to improve the approach to study haptophyte community composition, richness and proportional abundance by comparing two rRNA markers and scanning electron microscopy (SEM). Samples were collected in August 2013 at the Outer Oslofjorden, Norway. Total RNA/cDNA was amplified by haptophyte-specific primers targeting the V4 region of the 18S, and the D1-D2 region of the 28S rRNA. Taxonomy was assigned using curated haptophyte reference databases and phylogenetic analyses. Both marker genes showed Chrysochromulinaceae and Prymnesiaceae to be the families with highest number of Operational Taxonomic Units (OTUs), as well as proportional abundance. The 18S rRNA data setalso contained OTUs assigned to eight supported and defined clades consisting of environmental sequences only, possibly representing novel lineages from family to class. We also recorded new species for the area. Comparing coccolithophores by SEM with metabarcoding shows a good correspondence with the 18S rRNA gene proportional abundances. Our results contribute to link morphological and molecular data and 28S to 18S rRNA gene sequences of haptophytes without cultured representatives, and to improve metabarcoding methodology.
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| 9. |
- Jensen, Dan Funck
(författare)
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Identification of Expressed Genes During Infection of Chinese Cabbage (Brassica rapa subsp pekinensis) by Plasmodiophora brassicae
- 2011
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Ingår i: Journal of Eukaryotic Microbiology. - : Wiley. - 1066-5234 .- 1550-7408. ; 58, s. 310-314
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Tidskriftsartikel (refereegranskat)abstract
- Plasmodiophora brassicae is an obligate, biotrophic pathogen causing the club-root disease of crucifers. Despite its importance as a plant pathogen, little is known about P. brassicae at the molecular level as most of its life cycle takes place inside the plant host, and axenic culturing is impossible. Discovery of genes expressed during infection and gene organization are the first steps toward a better understanding of the pathogen-host interaction. Here, suppression subtractive hybridization was used to search for the P. brassicae genes expressed during plant infection. One-hundred and forty ESTs were found of which 49% proved to be P. brassicae genes. Ten novel P. brassicae genes were identified, and the genomic sequences surrounding four of the ESTs were acquired using genome walking. Alignment of the ESTs and the genomic DNA sequences confirmed that P. brassicae genes are intron rich and that the introns are small. These results show that it is possible to discover new P. brassicae genes from a mixed pool of both plant and pathogen cDNA. The results also revealed that some of the P. brassicae genes expressed in Chinese cabbage (Brassica rapa subsp. pekinensis) were identical to the genes expressed in the infection of Arabidopsis plants, indicating that these genes play an important role in P. brassicae infection.
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| 10. |
- Jensen, T, et al.
(författare)
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Cultured rat and purified human Pneumocystis carinii stimulate intra- but not extracellular free radical production in human neutrophils.
- 1998
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Ingår i: The Journal of eukaryotic microbiology. - 1066-5234. ; 45:5, s. 544-7
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Tidskriftsartikel (refereegranskat)abstract
- The production of free radicals in human neutrophils was studied in both Pneumocystis carinii derived from cultures of L2 rat lung epithelial-like cells and Pneumocystis carinii purified from human lung. Using the cytochrome C technique, which selectively measured extracellular superoxide generation, hardly any free radical production was observed after stimulation with cultured rat-derived P. carinii. A chemiluminescence technique, which separately measured intra- and extracellular free radical production, was subsequently employed to differentiate the free radical generation. It was established that 1) P. carinii stimulated intra- but not extracellular free radical production in human neutrophils, 2) opsonized cultured rat-derived P. carinii stimulated human neutrophils to a strong intracellular response of superoxide production, and 3) opsonized P. carinii, purified from human lung also stimulated human neutrophils to produce intracellular free radicals.
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| 11. |
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| 12. |
- Leblond, Jeffrey D., et al.
(författare)
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Sterols of the Green-Pigmented, Freshwater Raphidophyte, Gonyostomum semen, from Scandinavian Lakes
- 2013
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Ingår i: Journal of Eukaryotic Microbiology. - : Wiley. - 1066-5234 .- 1550-7408. ; 60:4, s. 399-405
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Tidskriftsartikel (refereegranskat)abstract
- Sterols are a class of membrane-reinforcing, ringed lipids which have a long history of examination in algae as a means of deriving chemotaxonomic relationships and as potential lipidic biomarkers. The Raphidophyceae represent a class of harmful, bloom-forming, marine and freshwater algae. To date, there have been four published examinations of their sterol composition, focusing primarily on brown-pigmented, marine species within the genera, Chattonella, Fibrocapsa, and Heterosigma. Lacking in these examinations has been the species Gonyostomum semen Ehrenb., which is a green-pigmented, freshwater raphidophyte with a worldwide distribution. The goal of this study was to examine the sterol composition of this nuisance alga, determine the potential of using its sterol profile as a biomarker, and finally to determine if there is any intraspecific variability between isolates. We have examined 21 isolates of G. semen from a number of Scandinavian lakes, and all were found to produce two major sterols, 24-ethylcholesta-5,22E-dien-3-ol and 24-ethylcholest-5-en-3-ol, and 24-methylcholest-5-en-3-ol as a minor sterol; the presence of 24-ethylcholesta-5,22E-dien-3-ol differentiates G. semen from brown-pigmented, marine raphidophytes which generally lack it. The results of this study indicate that isolates of G. semen from geographically separate lakes across Finland and Scandinavia have the same sterol biosynthetic pathway, and that there is no evolutionary divergence between the isolates with regard to sterol composition. The sterols of G. semen are not considered to be useful biomarkers for this particular organism because they are commonly found in other algae and plants.
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| 13. |
- Lentendu, G., et al.
(författare)
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Protist Biodiversity and Biogeography in Lakes From Four Brazilian River-Floodplain Systems
- 2019
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Ingår i: Journal of Eukaryotic Microbiology. - : Wiley. - 1066-5234 .- 1550-7408. ; 66:4, s. 592-599
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Tidskriftsartikel (refereegranskat)abstract
- The biodiversity and biogeography of protists inhabiting many ecosystems have been intensely studied using different sequencing approaches, but tropical ecosystems are relatively under-studied. Here, we sampled planktonic waters from 32 lakes associated with four different river-floodplains systems in Brazil, and sequenced the DNA using a metabarcoding approach with general eukaryotic primers. The lakes were dominated by the largely free-living Discoba (mostly the Euglenida), Ciliophora, and Ochrophyta. There was low community similarity between lakes even within the same river-floodplain. The protists inhabiting these floodplain systems comprise part of the large and relatively undiscovered diversity in the tropics.
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| 14. |
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| 15. |
- Mayor, Jordan
(författare)
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Comparing High-throughput Platforms for Sequencing the V4 Region of SSU-rDNA in Environmental Microbial Eukaryotic Diversity Surveys
- 2015
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Ingår i: Journal of Eukaryotic Microbiology. - : Wiley. - 1066-5234 .- 1550-7408. ; 62, s. 338-345
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Tidskriftsartikel (refereegranskat)abstract
- High-throughput sequencing platforms are continuing to increase resulting read lengths, which is allowing for a deeper and more accurate depiction of environmental microbial diversity. With the nascent Reagent Kit v3, Illumina MiSeq now has the ability to sequence the eukaryotic hyper-variable V4 region of the SSU-rDNA locus with paired-end reads. Using DNA collected from soils with analyses of strictly- and nearly identical amplicons, here we ask how the new Illumina MiSeq data compares with what we can obtain with Roche/454 GS FLX with regard to quantity and quality, presence and absence, and abundance perspectives. We show that there is an easy qualitative transition from the Roche/454 to the Illumina MiSeq platforms. The ease of this transition is more nuanced quantitatively for low-abundant amplicons, although estimates of abundances are known to also vary within platforms.
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| 16. |
- Montagnes, D. J. S., et al.
(författare)
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Redescription of Strombidium oculatum Gruber 1884 (Ciliophora, Oligotrichia)
- 2002
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Ingår i: Journal of Eukaryotic Microbiology. - 1066-5234. ; 49:4, s. 329-337
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Tidskriftsartikel (refereegranskat)abstract
- The marine, tide pool-dwelling ciliate Stombidium oculatum was redescribed using live, stained, SEM, and TEM material prepared from samples collected from pools on the Isle of Man (Irish Sea) and Brittany (France), Also, we reviewed the older German and French works that reported on ciliates collected in the Mediterranean and Brittany, respectively. The Brittany and Isle of Man populations of the ciliate were considered identical. Some morphological and behavioural differences exist between the Brittany-Isle of Man populations and the Mediterranean populations, but they were insufficient to distinguish different taxa. Thus, taxa from all three locations were considered to be conspecific. Key features used to describe the:ciliate were: morphology and ultrastructure of the free-swimming ciliate; cyst morphology; presence of mixotrophic-chloroplasts; presence of an eye spot composed of, stigma obtained from chlorophyte prey; division, morphogenesis, and nuclear structure; live observations and behaviour, including the encystment-excystment cycle. Based on morphological and behavioural characteristics the taxon was distinguished from other similar species, and a neotype has been designated as no type material exists.
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| 17. |
- Radek, Renate, et al.
(författare)
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Exclusive Gut Flagellates of Serritermitidae Suggest a Major Transfaunation Event in Lower Termites : Description of Heliconympha glossotermitis gen. nov spec. nov.
- 2018
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Ingår i: Journal of Eukaryotic Microbiology. - : WILEY. - 1066-5234 .- 1550-7408. ; 65:1, s. 77-92
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Tidskriftsartikel (refereegranskat)abstract
- The guts of lower termites are inhabited by host-specific consortia of cellulose-digesting flagellate protists. In this first investigation of the symbionts of the family Serritermitidae, we found that Glossotermes oculatus and Serritermes serrifer each harbor similar parabasalid morphotypes: large Pseudotrichonympha-like cells, medium-sized Leptospironympha-like cells with spiraled bands of flagella, and small Hexamastix-like cells; oxymonadid flagellates were absent. Despite their morphological resemblance to Pseudotrichonympha and Leptospironympha, a SSU rRNA-based phylogenetic analysis identified the two larger, trichonymphid flagellates as deep-branching sister groups of Teranymphidae, with Leptospironympha sp. (the only spirotrichosomid with sequence data) in a moderately supported basal position. Only the Hexamastix-like flagellates are closely related to trichomonadid flagellates from Rhinotermitidae. The presence of two deep-branching lineages of trichonymphid flagellates in Serritermitidae and the absence of all taxa characteristic of the ancestral rhinotermitids underscores that the flagellate assemblages in the hindguts of lower termites were shaped not only by a progressive loss of flagellates during vertical inheritance but also by occasional transfaunation events, where flagellates were transferred horizontally between members of different termite families. In addition to the molecular phylogenetic analyses, we present a detailed morphological characterization of the new spirotrichosomid genus Heliconympha using light and electron microscopy.
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| 18. |
- Santoferrara, Luciana, et al.
(författare)
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Perspectives from Ten Years of Protist Studies by High-Throughput Metabarcoding
- 2020
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Ingår i: Journal of Eukaryotic Microbiology. - : WILEY. - 1066-5234 .- 1550-7408. ; 67:5, s. 612-622
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Tidskriftsartikel (refereegranskat)abstract
- During the last decade, high-throughput metabarcoding became routine for analyzing protistan diversity and distributions in nature. Amid a multitude of exciting findings, scientists have also identified and addressed technical and biological limitations, although problems still exist for inference of meaningful taxonomic and ecological knowledge based on shortDNAsequences. Given the extensive use of this approach, it is critical to settle our understanding on its strengths and weaknesses and to synthesize up-to-date methodological and conceptual trends. This article summarizes key scientific and technical findings, and identifies current and future directions in protist research that uses metabarcoding.
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| 19. |
- Strassert, Jürgen F. H., et al.
(författare)
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Phylogeny, Evidence for a Cryptic Plastid, and Distribution of Chytriodinium Parasites (Dinophyceae) Infecting Copepods
- 2019
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Ingår i: Journal of Eukaryotic Microbiology. - : Wiley. - 1066-5234 .- 1550-7408. ; 66:4, s. 574-581
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Tidskriftsartikel (refereegranskat)abstract
- Spores of the dinoflagellate Chytriodinium are known to infest copepod eggs causing their lethality. Despite the potential to control the population of such an ecologically important host, knowledge about Chytriodinium parasites is limited: we know little about phylogeny, parasitism, abundance, or geographical distribution. We carried out genome sequence surveys on four manually isolated sporocytes from the same sporangium, which seemed to be attached to a copepod nauplius, to analyze the phylogenetic position of Chytriodinium based on SSU and concatenated SSU/LSU rRNA gene sequences, and also characterize two genes related to the plastidial heme pathway, hemL and hemY. The results suggest the presence of a cryptic plastid in Chytriodinium and a photosynthetic ancestral state of the parasitic Chytriodinium/Dissodinium clade. Finally, by mapping Tara Oceans V9 SSU amplicon data to the recovered SSU rRNA gene sequences from the sporocytes, we show that globally, Chytriodinium parasites are most abundant within the pico/nano- and mesoplankton of the surface ocean and almost absent within microplankton, a distribution indicating that they generally exist either as free-living spores or host-associated sporangia.
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| 20. |
- Tsuchiya, Masashi, et al.
(författare)
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Cytologic and Genetic Characteristics of Endobiotic Bacteria and Kleptoplasts of Virgulinella fragilis (Foraminifera)
- 2015
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Ingår i: Journal of Eukaryotic Microbiology. - : Wiley. - 1066-5234 .- 1550-7408. ; 62:4, s. 454-469
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Tidskriftsartikel (refereegranskat)abstract
- The benthic foraminifer Virgulinella fragilis Grindell and Collen 1976 has multiple putative symbioses with both bacterial and kleptoplast endobionts, possibly aiding its survival in environments from dysoxia (5-45mol-O-2/L) to microxia (0-5mol-O-2/L) and in the dark. To clarify the origin and function of V. fragilis endobionts, we used genetic analyses and transmission electron microscope observations. Virgulinella fragilis retained -proteobacteria concentrated at its cell periphery just beneath the cell membranes. Unlike another foraminifer Stainforthia spp., which retains many bacterial species, V. fragilis has a less variable bacterial community. This suggests that V. fragilis maintains a specific intracellular bacterial flora. Unlike the endobiotic bacteria, V. fragilis klepto-plasts originated from various diatom species and are found in the interior cytoplasm. We found evidence of both retention and digestion of kleptoplasts, and of fragmentation of the kleptoplastid outer membrane that likely facilitates transport of kleptoplastid products to the host. Accumulations of mitochondria were observed encircling endobiotic bacteria. It is likely that the bacteria use host organic material for carbon oxidation. The mitochondria may use oxygen available around the -proteobacteria and synthesize adenosine triphosphate, perhaps for sulfide oxidation.
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| 21. |
- Zlatogursky, Vasily V., et al.
(författare)
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The long-time orphan protist Meringosphaera mediterranea Lohmann, 1902 [1903] is a centrohelid heliozoan
- 2021
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Ingår i: Journal of Eukaryotic Microbiology. - : John Wiley & Sons. - 1066-5234 .- 1550-7408. ; 68:5
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Tidskriftsartikel (refereegranskat)abstract
- Meringosphaera is an enigmatic marine protist without clear phylogenetic affiliation, but it has long been suggested to be a chrysophyte-related autotroph. Microscopy-based reports indicate that it has a worldwide distribution, but no sequence data exist so far. We obtained the first 18S rDNA sequence for M. mediterranea (identified using light and electron microscopy) from the west coast of Sweden. Observations of living cells revealed granulated axopodia and up to 6 globular photosynthesizing bodies about 2 mu m in diameter, the nature of which requires further investigation. The ultrastructure of barbed undulating spine scales and patternless plate scales with a central thickening is in agreement with previous reports. Molecular phylogenetic analysis placed M. mediterranea inside the NC5 environmental clade of Centroplasthelida (Haptista) along with additional environmental sequences, together closely related to Choanocystidae. This placement is supported by similar scales in Meringosphaera and Choanocystidae. We searched the Tara Oceans 18S V9 metabarcoding dataset, which revealed four OTUs with 94.8%-98.2% similarity, with oceanic distribution similar to that based on morphological observations. The current taxonomic position and species composition of the genus are discussed. The planktonic lifestyle of M. mediterranea contradicts the view of some authors that centrohelids enter the plankton only temporarily.
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