| 1. |
- Alfjorden, Anders, et al.
(author)
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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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In: JOURNAL OF EUKARYOTIC MICROBIOLOGY. - 1066-5234 .- 1550-7408.
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Journal article (peer-reviewed)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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| 2. |
- Brinkmann, Inda, et al.
(author)
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Through the eDNA looking glass: Responses of fjord benthic foraminiferal communities to contrasting environmental conditions
- 2023
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In: Journal of Eukaryotic Microbiology. - : Wiley. - 1066-5234 .- 1550-7408. ; 70:4
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Journal article (peer-reviewed)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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| 3. |
- Santoferrara, Luciana, et al.
(author)
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Perspectives from Ten Years of Protist Studies by High-Throughput Metabarcoding
- 2020
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In: Journal of Eukaryotic Microbiology. - : WILEY. - 1066-5234 .- 1550-7408. ; 67:5, s. 612-622
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Journal article (peer-reviewed)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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| 4. |
- Zlatogursky, Vasily V., et al.
(author)
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The long-time orphan protist Meringosphaera mediterranea Lohmann, 1902 [1903] is a centrohelid heliozoan
- 2021
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In: Journal of Eukaryotic Microbiology. - : John Wiley & Sons. - 1066-5234 .- 1550-7408. ; 68:5
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Journal article (peer-reviewed)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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