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Species belonging to Raphidophyceae and resembling species of Dictyochophyceae E and J . Chattonella antiqua A , Chattonella marina B , A cyst of Chattonella C , Chattonella ovata D , Vicicitus globosus formerly Chattonella globosa E , Heterosigma akashiwo F , A cyst of Heterosigma akashiwo G , Fibrocapsa japonica H , A cyst of Fibrocapsa japonica I , Pseudochattonella verruculosa formerly Chattonella verruculosa J . Scale bars, A-E20 μm, F-J10 μm. The picture cyst of F. japonica was cited from Yoshimatsu 1987
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Plankton are aquatic organisms unable to swim against the current, and they include diverse taxa of different phylogenetic origins. The taxonomy, phylogeny and ecology of nine plankton groups are reviewed in this paper, in order to comprehensively understand the latest information and current situation of plankton studies. The order-level classific...
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Abstract Background The parasitic dinoflagellates of the genus Hematodinium represent the causative agent of so-called bitter or pink crab disease in a broad range of shellfish taxa. Outbreaks of Hematodinium-associated disease can devastate local fishing and aquaculture efforts. The goal of our study was to examine the potential role of the common...
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... steps removed 12.1-98.1% of the original sequence reads in the samples. OTUs were identified to the genus or species level using Genbank and assigned to phylum-or class-level taxa according to 15,16 . Relative abundances were derived from the ratio of total sequence reads and the sequence reads of each higher taxon. ...
DNA metabarcoding (DNA-MB) targeting the whole plankton community is a promising approach in studies of sediment samples from water bodies, but its effectiveness in ancient material is not well demonstrated. We applied DNA-MB of plankton in a sediment core to reconstruct the paleo-environment of Lake Shinji, Japan, through a marine lagoon/freshwater lake transition during the past 2300 years. We interpreted core-sample plankton taxonomy and habitat by reference to the modern plankton community in water samples. OTUs (operational taxonomic units) belonging to Dictyochophyceae were 81.05% of the total reads in sediments. However, Ciliophora, Copepoda and Labyrinthulea formed the majority of plankton taxa in the water samples, suggesting that they are under-represented in sediment. A drastic change in plankton composition correlated with a large decrease in sediment sulfur concentration, implying the change of aquatic environment from marine lagoon to freshwater lake. This event took place ca. 1200 CE in Lake Shinji. A 250 year-long transitional period followed, during which the total DNA sequence reads were very low. This suggests that salinity fluctuations created a hostile environment for both marine and freshwater plankton species. Our results show that DNA-MB of the whole plankton community is effective in reconstructing paleo-environments.
... However, some sequences difficult to identify by BLASTN were (1) further identified by SILVA (Quast et al., 2013) and/or (2) assigned taxonomic names by creating phylogenetic trees containing sequences of related organisms. The classification of phylum-or class-level taxa is referred to by Adl et al. (2019) and Nakamura, Matsuoka, et al. (2019). The relative abundance (%) was derived from the ratio of the total sequence read and the sequence read of each higher taxon. ...
DNA metabarcoding on a single organism is a promising approach to clarify the biological interactions (e.g., predator-prey relationships and symbiosis, including parasitism) of difficult-to-culture protists. To evaluate the effectiveness of this method, Radiolaria and Phaeodaria, which are ecologically important protistan groups, were chosen as target taxa. DNA metabarcod-ing on a single organism focused on the V9 region of the 18S rRNA gene revealed potential symbionts, parasites and food sources of Radiolaria and Phaeodaria. Previously reported hosts and symbionts (parasites) were detected, and newly recognized combinations were also identified. The contained organisms largely differed between Radiolaria and Phaeodaria. In Radiolaria, members of the same order tended to contain similar organisms, and the taxonomic composition of possible symbionts, parasites, and food sources was fixed at the species level. Members of the same phaeodarian family, however, did not contain similar organisms, and body part (i.e., the central capsule or the phaeodium) was the most important factor that divided the taxonomic composition of detected organisms, implying that the selection of appropriate body part is important when trying to ascertain contained organisms, even for unicellular zooplankton. Our results show that DNA metabarcoding on a single organism is effective in revealing the biological interactions of difficult-to-culture protists.
... Rhizaria are a supergroup of unicellular eukaryotes, mainly composed of mineralized skeleton-bearing protists such as Foraminifera, Radiolaria, and Phaeodaria (Nakamura et al., 2019a). Some species of rhizarians (Phaeodaria and Radiolaria) and crustaceans (Amphipoda and Decapoda) show a unique symbiotic relationship (Wakabayashi et al., 2017;Nakamura & Suzuki, 2019), called the rhizarian rider phenomenon (Nakamura et al., 2019b). ...
... Radiolaria consist of five orders (Collodaria, Nassellaria, Spumellaria, Acantharia, together with Taxopodia) (Nakamura et al., 2019;Suzuki and Aita, 2011;Suzuki and Not, 2015), while the former member Phaeodaria has migrated to the Certozoa (Polet et al., 2004;Yuasa et al., 2006). Radiolarians are widely distributed in the shallowto-open oceans (Wang, 2012), are dispersed horizontally across the world's oceans, including arctic, subtropical, and tropical waters, and are distributed vertically from the surface to 8000 m water depth (Suzuki and Aita, 2011;Suzuki and Not, 2015;Wang, 2003). ...
... Classification was performed mainly based on the newest system (Nakamura et al., 2019;Suzuki and Not, 2015). Identification was conducted primarily following the radiolarian monographs of Zhang and Suzuki (2017) and , as they summarized the taxonomy of the Radiolaria, especially Holocene pylonioid radiolarians, and the radiolarian monographs of offshore China (Chen and Tan, 1996;Tan, 1998;Tan and Su, 2003). ...
In this study, we analyzed 45 surface sediment samples collected in the marginal seas of the Western North Pacific, including the South China Sea, the East China Sea, and the Philippine Sea, to investigate the radiolarian assemblages and their relationship with upper layer environmental conditions. Based on the results of Q-mode cluster analysis, the radiolarian assemblages can be divided into four clusters, corresponding to the North Equatorial Current assemblage, North Equatorial Current Bifurcation assemblage, Kuroshio–South China Sea assemblage, and Kuroshio–East China Sea assemblage. Winter sea surface temperature (SSTw), winter sea surface salinity (SSSw), and annual silicate concentration were the most significant environmental variables associated with the radiolarian assemblages, among which SSTw showed the highest correlation with the radiolarian fauna. The significant influences of SSTw and SSSw suggested that the seasonal change of the North Equatorial Current–Kuroshio Current system exerted a crucial effect on the abundance and distribution pattern of the radiolarian fauna.
