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        <title>Frontiers in Protistology | New and Recent Articles</title>
        <link>https://www.frontiersin.org/journals/protistology</link>
        <description>RSS Feed for Frontiers in Protistology | New and Recent Articles</description>
        <language>en-us</language>
        <generator>Frontiers Feed Generator,version:1</generator>
        <pubDate>2026-05-13T08:12:49.947+00:00</pubDate>
        <ttl>60</ttl>
        <item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frpro.2026.1787250</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frpro.2026.1787250</link>
        <title><![CDATA[Development of an indirect immunofluorescence assay for detecting ciguatoxin-producing microalgae]]></title>
        <pubdate>2026-03-11T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Shota Ohara</author><author>Goshi Araki</author><author>Takashi Kadono</author><author>Haruo Yamaguchi</author><author>Takeshi Tsumuraya</author><author>Kirsty F. Smith</author><author>Lesley L. Rhodes</author><author>Masao Adachi</author>
        <description><![CDATA[The seafood illness, ciguatera poisoning (CP) is a significant public health concern in tropical and subtropical regions worldwide. In Japan, CP is particularly prevalent in Okinawa Prefecture, where is the subtropical region of Japan, due to the consumption of fish contaminated with Pacific ciguatoxins (P-CTXs). The benthic dinoflagellate Gambierdiscus polynesiensis is known to produce P-CTXs in the South Pacific, but P-CTX-producing microalgae have not been identified in Japanese waters. A practical method applicable to field samples containing diverse benthic microalgae is therefore required. To identify a P-CTX producer in Japan, an indirect immunofluorescence (IIF) assay using P-CTX-specific monoclonal antibodies that can be applied to various benthic microalgae such as diatoms and dinoflagellates was developed. The optimal conditions for cell membrane permeabilization were determined using the IIF assay with an anti-actin antibody on benthic diatoms and dinoflagellates treated with various concentrations of Triton X-100. Treatment of the cells with 5.0% (v/v) Triton X-100 resulted in the highest fluorescence and the lowest cell loss. When an IIF assay with an anti-P-CTX antibody (8H4) was performed on cells of Gambierdiscus australes, G. jejuensis, G. polynesiensis, and G. silvae treated with 5.0% Triton X-100, only G. polynesiensis showed fluorescence. The simultaneous application of two anti-P-CTX antibodies (8H4 and 10C9) doubled the fluorescence compared to 8H4 alone. Extending the antibody reaction time from one hour to 16 hours increased the fluorescence by about sevenfold. These optimized conditions enabled visualization of P-CTXs-derived fluorescence in G. polynesiensis cells under both not only a confocal laser scanning microscope but also a conventional inverted fluorescence microscope having deeper depths of focus. Combining the IIF assay with observing the cells under an inverted microscope provides a practical tool for detecting P-CTX producers in samples of various sizes of benthic microalgae collected from coastal waters. This will contribute to identifying unknown P-CTX-producing microalgae in Japanese and other coastal waters in the future.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frpro.2026.1743384</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frpro.2026.1743384</link>
        <title><![CDATA[18S rDNA metabarcoding unveils trophic interactions between Neogloboquadrina pachyderma and the pelagic eukaryotic community in Prydz Bay, East Antarctica]]></title>
        <pubdate>2026-02-02T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Tushar Kaushik</author><author>Vaishnavi Dixit</author><author>Rahul Mohan</author>
        <description><![CDATA[Neogloboquadrina pachyderma is the dominant planktonic foraminiferal species in polar oceans and a major contributor to biogenic carbonate production in the Southern Ocean. Its calcite test serves as a key geochemical archive for reconstructing past ocean conditions through stable isotope and trace element proxies. As polar marine ecosystems undergo rapid environmental change, understanding the ecological associations and trophic dependencies of N. pachyderma within surrounding pelagic communities is increasingly important, particularly in extreme Antarctic environments. Here, we present the first molecular characterization of pelagic eukaryotic assemblages associated with individual N. pachyderma (genetic Type IV) specimens collected from Prydz Bay, East Antarctica, using a single-cell 18S rRNA gene metabarcoding approach. High-throughput sequencing revealed that the N. pachyderma eukaryome was dominated by dinoflagellates (Dinophyceae), diatoms (Bacillariophyceae), radiolarians, Syndiniales, and metazoans. In contrast, ambient seawater communities were enriched in cercozoans, followed by dinoflagellates, radiolarians, and ciliates. The distinct composition of eukaryotic assemblages associated with N. pachyderma relative to the surrounding seawater suggests selective incorporation of a subset of the local pelagic eukaryotic pool, potentially reflecting trophic interactions or transient associations with aggregate-associated prey. These results provide preliminary molecular insights into the trophic linkages or pelagic eukaryotic associations of Antarctic N. pachyderma Type IV, in Prydz Bay, East Antarctica, and establish an important baseline for future investigations. Our findings highlight the role of pelagic eukaryotes in shaping foraminiferal microbial interactions and underscore the relevance of such associations for interpreting palaeoceanographic proxies in a rapidly changing Southern Ocean.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frpro.2025.1663791</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frpro.2025.1663791</link>
        <title><![CDATA[Integrative taxonomy, whole organelle genomes and endosymbiosis in Rhopalodia sterrenburgii Krammer]]></title>
        <pubdate>2025-10-20T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Aimee Caye G. Chang</author><author>Mailor W. W. Amaral</author><author>Kyle G. Keepers</author><author>Megan Greenwood</author><author>Jingchun Li</author><author>Sarah E. Hamsher</author><author>Scott R. Miller</author><author>J. Patrick Kociolek</author>
        <description><![CDATA[Despite their ecological significance and unique endosymbiotic capabilities, diatoms in the genus Rhopalodia remain poorly represented in genomic databases, particularly with respect to the availability of complete genomes from multiple organellar compartments. This study addresses that gap by presenting, for the first time, the complete chloroplast (133,086 bp), mitochondrial (36,786 bp), and spheroid body (3,024,495 bp) genomes of Rhopalodia sterrenburgii, a nitrogen-fixing diatom with a cyanobacterial endosymbiont. Phylogenetic reconstruction based on five genes from different cellular compartments (18S, 28S, rbcL, psbC, cob) placed R. sterrenburgii as a basal lineage relative to R. gibba (Rhopalodia sensu lato) and the Epithemia sensu stricto species E. argus, E. turgida, and E. sorex, providing new insights into evolutionary relationships within Rhopalodiales. Additionally, pathway analysis revealed the progressive loss of genes involved in vitamin B12 and chlorophyll a biosynthesis in more recently diverged Rhopalodia and Epithemia lineages. Our findings support a pattern of genome reduction in symbiotic diazotrophic diatoms, potentially driven by coevolution with their endosymbionts, and an increasing reliance on integrated metabolic functions between the host and the endosymbiont.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frpro.2025.1612811</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frpro.2025.1612811</link>
        <title><![CDATA[Vertical distribution of harmful algae in the sediment of Uranouchi Inlet by metabarcoding]]></title>
        <pubdate>2025-06-30T00:00:00Z</pubdate>
        <category>Brief Research Report</category>
        <author>Hiroshi Funaki</author><author>Chetan Chandrakant Gaonkar</author><author>Tomohiro Nishimura</author><author>Kouki Tanaka</author><author>Kaito Kamimura</author><author>Tatsuya Kaji</author><author>Keizo Nagasaki</author><author>Masao Adachi</author>
        <description><![CDATA[Uranouchi Inlet, situated on the Pacific coast of southwestern Japan, has been a highly enclosed inlet known for yellowtail farming since 1959. Since the 1980s, harmful algal blooms (HABs) have repeatedly occurred, resulting in mass mortality of fish and shellfish. In the sediment at the inlet, the resulting cysts of the HAB species may be preserved, which reflects the history of HAB events. However, the vertical distributions of HAB species in sediment have not been elucidated. In this study, core sediment samples were analyzed by metabarcoding. The dating of each sample was cited from previous study dating the same samples. The findings revealed the presence of eleven HAB species, with notable shifts from approximately 1977–1988. The timing of the shifts corresponded to that of the development of aquaculture and the resulting eutrophication. Vertical core metabarcoding provides footprints of how HAB species composition may be influenced by anthropogenic environmental changes.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frpro.2025.1587784</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frpro.2025.1587784</link>
        <title><![CDATA[New molecular markers for quantifying abundance and gene expression of widespread and often undetected marine N2 fixing symbionts of diatoms]]></title>
        <pubdate>2025-06-25T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Linnéa M. V. Ström</author><author>Philip Ley</author><author>Eric A. Webb</author><author>David A. Hutchins</author><author>Mak Saito</author><author>Daniel Lundin</author><author>Rachel A. Foster</author>
        <description><![CDATA[IntroductionDecades of research has been devoted to understanding the occurrence, distribution, and activity of different N2-fixers in the oceans. Marine N2-fixing diatom symbioses involving the heterocyst-forming cyanobacterium Richelia are widespread, yet often go undetected. Some of the diatom-Richelia symbioses have the advantage to be identified by microscopy, however, observations alone cannot inform on the metabolic state of a cell. MethodsHere, we developed nine new specific quantitative PCR assays that detect three common symbiotic Richelia strains (ReuHH01, RintRC01, RrhiSC01) of diatoms based on molecular markers for: a high affinity phosphate transporter (pstS), an iron transporter (exbB), and a constitutively expressed gene (rnpA, protein component of ribonuclease P). We first tested the new assays in the lab, including a diel experiment to elucidate the temporal dynamics of gene expression for each molecular marker, then applied the new assays to field collected samples. In the field we also made microscopy observations of the diatom-Richelia symbioses and measured bulk N2 and Carbon (C) fixation rates with stable isotope labelling incubations. ResultsThe number of genes encoding the molecular markers varied; typically, fewer in the endobiont strains. Detection in field samples based on qPCR was consistent with microscopy observations. The environmental gene expression for all the new targets, and additionally nifH for N2 fixation (nitrogenase) were low, and highest expression was detected in the upper water column (0-40 m) consistent with higher densities of the Richelia by qPCR and microscopy observations. Low in situ bulk rates of N2 and C fixation corroborated the aforementioned low nifH expression. Expression of both nifH and pstS was temporally regulated in the lab experiment of the facultative symbiotic Richelia strain RrhiSC01 with higher expression in the early and late photoperiods, respectively. DiscussionThe nine new assays are an improvement over the previous assays based on the nifH gene as cross-reactivity between Richelia strains is minimum, expression can be normalized to rnpA, and expression is informative of the symbiont nutrient status.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frpro.2025.1512258</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frpro.2025.1512258</link>
        <title><![CDATA[Novel ultrastructural features of the nucleus of the ancestral dinoflagellate Oxyrrhis marina as revealed by freeze substitution fixation and volume electron microscopy]]></title>
        <pubdate>2025-02-20T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Yasuhiro Fukuda</author><author>Toshinobu Suzaki</author><author>Kazuyoshi Murata</author><author>Chihong Song</author>
        <description><![CDATA[IntroductionOxyrrhis marina is thought to have diverged from other dinoflagellates at an early stage of their evolution and is considered to show their ancestral form. As for other current dinoflagellates, the species possesses condensed chromosomes throughout the cell cycle but shows some important differences. The chromosomes of O. marina are thinner and longer than those of other dinoflagellate species and do not show the repeating arch-shaped liquid-crystal structure that is found in core dinoflagellates. These morphological features were described originally about half a century ago from cells fixed using conventional chemical methods, which are prone to producing morphological artifacts. Therefore, it is crucial to reevaluate ultrastructural features using cells fixed by other methods.MethodIn this study, O. marina was fixed with freeze-substitution, a method that is less prone to artifacts in electron microscopy, in addition to conventional chemical fixation, and the details of chromosome structure were reexamined using volume electron microscopy.ResultsIn the four cells observed, the number of chromosomes was consistently nearly 400. The nucleus of O. marina has a single nucleolus at its center, to which, as in other dinoflagellates, multiple chromosomes are attached. Several nucleofilaments were observed penetrating the nucleolus. On the other hand, filamentous structures have been observed in chemically fixed chromosomes, but no such structures were observed in cells fixed by freeze-substitution. Tomographic analysis using volume electron microscopy confirmed the absence of these structural features.DiscussionThe number of chromosomes of O. marina was previously considered to be approximately 50, but this is only one-eighth of the number found in the present study (400). It is concluded that the chromosomes of O. marina are composed of tightly condensed and densely folded nucleofilaments, which are difficult to distinguish. This study revealed novel ultrastructural features in the chromosome of O. marina. These findings will help consider the evolutionary scenario through which the enigmatic dinoflagellate nucleus (dinokaryon) was established. In addition, this study indicated freeze-substitution fixation and volume electron microscopy would become a critical technique in elucidating the dinokaryon chromosome structure.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frpro.2024.1428985</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frpro.2024.1428985</link>
        <title><![CDATA[Variability of winter cooling affects intensity of phytoplankton spring blooms – how resilient is the ciliate assemblage composition to changes in food availability?]]></title>
        <pubdate>2024-08-12T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Martina Schalch-Schuler</author><author>Alfred Wüest</author><author>Gianna Dirren-Pitsch</author><author>Rafael Niedermann</author><author>Barbara Bassin</author><author>Oliver Köster</author><author>Jakob Pernthaler</author><author>Thomas Posch</author>
        <description><![CDATA[After years of partial winter mixing in Lake Zurich (Switzerland), a complete turnover of the water column reoccurred during winter/spring 2021. It was favored by a cold, windy winter and a small difference of water temperatures between the surface zone and a hypolimnion (deep water zone) that had gradually warmed during the previous years. The trend of declining phytoplankton spring blooms due to incomplete winter mixing was interrupted by mass development of algae due to the upwelling of nutrients accumulated in the hypolimnion. The effects of this singular deep mixing on the microbial food web during spring were studied in a high-frequency sampling campaign and compared with data from two years of partial winter mixing (2020 and 2022). A particular focus was put on the quantitative composition of the ciliate assemblage. Our results showed that not all organisms reacted equally to the nutrient (phosphorus) boost in the surface zone. Centric diatoms and cryptophytes profited most directly from the deep mixing, outcompeting the otherwise dominant cyanobacterium Planktothrix rubescens. Heterotrophic bacteria and their top predators, the ‘heterotrophic nanoflagellates’ trophic guild, were less affected by the nutrient supply and showed only short-lived increases of maximal biomass. The assemblage composition of ciliate morphotypes was highly resilient over the three years, presumably due to the range of acceptable food items of the predominant omnivorous species. However, numerous ciliate morphotypes showed brief mass development in 2021, and Balanion planctonicum, small Urotricha species and tintinnids were significantly more frequent than in 2020/2022. Small interception-feeding morphotypes apparently profited from the rich supply of their cryptomonad food, and tintinnid morphotypes additionally benefited from the availability of building material (e.g., centric diatom shells) for their loricae. In summary, we show that effects of lake warming in deep stratifying lakes are not as unidirectional as previously presumed, and we reveal resilience of the pelagic ciliate morphotype assemblage to lake warming related interannual variability in Lake Zurich.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frpro.2024.1422481</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frpro.2024.1422481</link>
        <title><![CDATA[Characterization and inter-strain variability in ichthyotoxicity of Heterocapsa ovata (Peridiniales, Dinophyceae) from temperate waters of South Australia]]></title>
        <pubdate>2024-06-26T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Arjun Verma</author><author>Greta Gaiani</author><author>Mona Hoppenrath</author><author>Juan Jose Dorantes-Aranda</author><author>Kirsty Smith</author><author>Gurjeet Singh Kohli</author><author>Clinton Wilkinson</author><author>Gustaaf Marinus Hallegraeff</author><author>Shauna Ann Murray</author>
        <description><![CDATA[IntroductionHarmful algal bloom (HAB)-forming species and populations exhibit substantial intraspecific functional trait variation, which can confer eco-evolutionary advantages. Phenotypic variability among populations can buffer the immediate detrimental effects of environmental fluctuations, with more diverse populations expected to survive changing conditions more efficiently than their uniform counterparts.MethodsIn February 2014, a mixed fish-killing dinoflagellate bloom occurred in the temperate waters of Coffin Bay, South Australia, causing the death of oysters and fish in the area. The bloom was dominated by Karenia mikimotoi and a cryptic species of Heterocapsa. Twenty-one monoclonal Heterocapsa isolates were established from the site and identified as H. ovata using microscopy and universal ribosomal markers (ITS/5.8S and LSU D1/D3 rDNA regions; SSU and cob were used for amplicon sequencing). These isolates were tested for ichthyotoxicity using a bioassay based on cells from the gills of rainbow trout (Oncorhynchus mykiss). Culture fraction preparations (whole cells, supernatant, and lysed cells) were analyzed to determine ichthyotoxicity levels.ResultsThe highest ichthyotoxicity was observed in lysed cells, with surprisingly high inter-strain variability. This suggests that different strains of H. ovata have varying levels of toxicity.DiscussionResults from this study expand our understanding of the adaptive strategies of HAB species and enable predictions of future population dynamics under changing climatic conditions. The substantial phenotypic variability among H. ovatastrains highlights the potential for diverse responses to environmental stressors, underscoring the importance of considering intraspecific variation in ecological and evolutionary studies of HABs.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frpro.2024.1320917</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frpro.2024.1320917</link>
        <title><![CDATA[Nuclear genomes of dinoflagellates reveal evolutionarily conserved pattern of RNA editing relative to stress response]]></title>
        <pubdate>2024-05-10T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Yibi Chen</author><author>Katherine E. Dougan</author><author>Debashish Bhattacharya</author><author>Cheong Xin Chan</author>
        <description><![CDATA[Dinoflagellates are a group of diverse protists with complex genomes whose gene expression regulation mechanisms remain little known. RNA editing is a post-transcriptional regulatory mechanism of gene expression utilized by diverse species, and has been described primarily in the plastid and mitochondrial genomes of dinoflagellates. Its role in post-transcriptional regulation in the nuclear genomes of dinoflagellates remains largely unexplored. Here, integrating genome and transcriptome data from two dinoflagellate taxa in a comparative analysis, we identified 10,486 and 69,953 putative RNA editing sites in the nuclear genomes of the coral symbiont, Durusdinium trenchii CCMP2556 and the free-living bloom-forming taxon, Prorocentrum cordatum CCMP1329. We recovered all 12 possible types of RNA edits, with more edits representing transitions than transversions. In contrast to other eukaryotes, we found a dominance of A-to-T transversion in non-coding regions, many of which were condition-specific. Overall, the RNA editing sites implicate 7.5% of D. trenchii genes and 13.2% of P. cordatum genes. Some sites (1.5% in D. trenchii and more-substantially 62.3% in P. cordatum) were edited at significantly different frequencies in distinct growth conditions. The distribution of editing types and locations exhibited conserved patterns between the two phylogenetically distant species. Interestingly, A-to-T editing within the untranslated regions appear to be associated with upregulation of the edited genes in response to heat stress. These results lend support to the hypothesis that RNA editing is a key molecular mechanism that underpins regulation of gene expression in dinoflagellates.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frpro.2024.1376877</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frpro.2024.1376877</link>
        <title><![CDATA[Contaminant or goldmine? In silico assessment of Symbiodiniaceae community using coral hologenomes]]></title>
        <pubdate>2024-04-02T00:00:00Z</pubdate>
        <category>Mini Review</category>
        <author>Hisatake Ishida</author><author>Cynthia Riginos</author><author>Cheong Xin Chan</author>
        <description><![CDATA[Endosymbiotic dinoflagellates of the family Symbiodiniaceae are symbionts essential to corals and other marine organisms. A coral holobiont consists of the coral host, Symbiodiniaceae, and other microbes that together sustain the overall productivity and coral health. Coral hologenome data, generated from all interacting components of a coral holobiont, are key for elucidating the molecular mechanisms that underpin the resilience of the holobiont to changing environments. Although coral hologenome data are often dominated by host coral genomic sequences, they provide an avenue for recovering genomic sequences from Symbiodiniaceae in hospite. Here, we review recent advances in the approaches for assessing community diversity of in hospite Symbiodiniaceae from coral hologenome data. Using a case study based on existing hologenome datasets of the Acropora kenti coral, we highlight how hologenome datasets in large numbers can provide a useful analysis platform for assessing Symbiodiniaceae diversity and their function in coral holobionts.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frpro.2024.1320353</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frpro.2024.1320353</link>
        <title><![CDATA[Diversity of lipid profiles of Symbiodiniaceae under temperature and nutrient stress]]></title>
        <pubdate>2024-02-27T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Laura M. La Motta</author><author>Matthew P. Padula</author><author>Brigitte Sommer</author><author>Emma F. Camp</author><author>Jennifer L. Matthews</author>
        <description><![CDATA[Lipid-based survival mechanisms allow microalgae to occupy wide geographical ranges and survive abiotic stress. The protist Symbiodiniaceae are globally distributed from temperate to tropical environments, and establish mutualisms with numerous hosts, including cnidarians. The ability for these dinoflagellates to maintain cellular function under wide ranging environmental conditions will influence the survival and geographic distribution of their hosts. One mechanism that microalgae utilize to adapt to environmental changes is lipid remodeling, such as increased saturation of membranes to maintain the structural integrity under temperature changes, and lipid accumulation when nutrient availability decreases. Whether Symbiodiniaceae utilize lipid remodeling to adapt to sublethal environmental change is yet to be resolved. This study examines the effects of temperature (16°C to 31°C), and nitrogen (N) and phosphorus (P) availability, on the lipid composition and physiology of cultured Symbiodiniaceae (from genera Breviolum, Cladocopium and Durusdinium) isolated from temperate or tropical environments. Glycerolipids, particularly triacyclglycerols, increased while cell size decreased under N- and NP-nutrient limited cultures, across all Symbiodiniaceae species. P-limitation caused a decrease in phosphatidylcholine, an important membrane lipid, and saw an increase in isoprenol lipids. This suggests a diversion of phosphorus from phospholipid membranes to the biosynthesis of membrane-stabilizing isoprenes. Reduced photophysiology under P-limitation in all Symbiodiniaceae further supports evidence that P-limitation induced stress in these Symbiodiniaceae cells. As expected, growth rate was reduced in all Symbiodiniaceae at temperature extremes (31°C). Significant increases in oxidized lipids, particularly oxidized phosphatidylinositol, and a reduction in ether-linked phospholipids in cultures grown at 31°C, suggests increased reactive oxygen species (ROS) abundance in these cells. In addition, at 31 °C, D. trenchii and both C. goreaui spp. cell size increased, a common sign of ROS accumulation, cell cycle arrest and necrosis. The observed increases in lipid energy storage (triacylglycerols and isoprenoids) under nutrient stress, as well as ROS-mitigation via lipid remodeling leading to increases in saturated fatty acids and oxidized lipids under temperatures stress, suggest Symbiodiniaceae can remodel their lipids to adapt to environmental shifts. If similar mechanisms occur in hospite, this could be an adaptive strategy for coral holobionts under a changing climate.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frpro.2024.1302560</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frpro.2024.1302560</link>
        <title><![CDATA[Deleterious effects of free fatty acids and hydrogen peroxide towards the dinoflagellate Gymnodinium catenatum]]></title>
        <pubdate>2024-02-07T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Martín Fernando Encinas-Yánez</author><author>Christine Johanna Band-Schmidt</author><author>Tania Zenteno-Savín</author><author>Ignacio Leyva-Valencia</author><author>Leyberth José Fernández Herrera</author><author>Elena Palacios-Mechetnov</author>
        <description><![CDATA[Allelopathy refers to biochemical interactions among competing microalgae, it involves a donor species that produces metabolites which can cause inhibitory effects on susceptible species. This phenomenon can participate in the regulation of harmful algal blooms. The dinoflagellate Gymnodinium catenatum is negatively affected by allelopathic interactions with co-occurring microalgae species, like Chattonella marina var. marina, which has been suggested to produce reactive oxygen species (ROS) and free fatty acids (FFA) as nocive and allelopathic agents. This study explored the effect of hydrogen peroxide (H2O2) and the main fatty acids produced by C. marina. An analysis of fatty acids content of C. marina in exponential phase detected 16:0 (12.5 ± 0.01%), 18:4ω-3 (15.4 ± 0.36%) and 20:5ω-3 (35.4 ± 0.71%) as the most abundant. These fatty acids along with H2O2 were used in dose-response bioassays with cultures of G. catenatum in exponential phase. Results suggest that these substances affect cell morphology, including the loss of motility and signs of chlorosis, as well as the chain forming qualities of G. catenatum. Toxicity among these substances varied, suggesting that the polyunsaturated fatty acid 18:4ω-3 can potentially act as a more effective allelochemical (LD50 = 1.7 ± 0.19 mg L-1 at 24 h), followed by 20:5ω-3 (LD50 = 3.6 ± 0.17 mg L-1 at 24 h) and the saturated fatty acid 16:0 (LD50 = 6.2 ± 1.05 at 48 h). Our results suggest these substances can act, at least partially, as allelochemicals, with PUFA being the most effective metabolites. These results contribute in elucidating the potential role of ROS and FFA in allelopathy in marine phytoplankton communities.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frpro.2023.1305634</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frpro.2023.1305634</link>
        <title><![CDATA[Molecular approaches and challenges for monitoring marine harmful algal blooms in a changing world]]></title>
        <pubdate>2024-01-16T00:00:00Z</pubdate>
        <category>Mini Review</category>
        <author>Kirsty F. Smith</author><author>Jacqui Stuart</author><author>Lesley L. Rhodes</author>
        <description><![CDATA[Harmful algal blooms (HABs) of marine microalgae are a growing concern globally and many studies predict that their occurrence, range, and toxicity may increase with climate change, highlighting the need for responsive and adaptable monitoring techniques. Monitoring programmes for HABs require appropriate sampling techniques, accurate and quantitative identification of potentially toxic taxa, and the ability to respond to novel species or HAB events. These challenges have made it difficult to move past traditional techniques, but research tools are continuing to be developed to bring new opportunities for both monitoring programmes and fundamental understanding of these globally significant organisms within a changing landscape.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frpro.2023.1328026</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frpro.2023.1328026</link>
        <title><![CDATA[Dinophysis, a highly specialized mixoplanktonic protist]]></title>
        <pubdate>2024-01-08T00:00:00Z</pubdate>
        <category>Mini Review</category>
        <author>Beatriz Reguera</author><author>María García-Portela</author><author>Esther Velasco-Senovilla</author><author>Pilar Rial</author><author>Laura Escalera</author><author>Patricio A. Díaz</author><author>Francisco Rodríguez</author>
        <description><![CDATA[Several Dinophysis species produce lipophilic toxins (diarrhetic shellfish poisoning, DSP and pectenotoxins PTX) which are transferred through the food web. Even at low cell densities (< 103 cell L-1), they can cause human illness and shellfish harvesting bans; toxins released into the water may kill early life stages of marine organisms. Dinophysis species are mixotrophs: they combine phototrophy (by means of kleptoplastids stolen from their prey) with highly selective phagotrophy on the ciliate Mesodinium, also a mixotroph which requires cryptophyte prey of the Teleaulax/Geminigera clade. Life cycle strategies, biological interactions and plastid acquisition and functioning in Dinophysis species make them exemplars of resilient holoplanktonic mixoplankters and of ongoing speciation and plastidial evolution. Nevertheless, 17 years after the first successful culture was established, the difficulties in isolating and establishing cultures with local ciliate prey, the lack of robust molecular markers for species discrimination, and the patchy distribution of low-density populations in thin layers, hinder physiological experiments to obtain biological measurements of their populations and slow down potential advances with next-generation technologies. The Omic’s age in Dinophysis research has only just started, but increased efforts need to be invested in systematic studies of plastidic diversity and culture establishment of ciliate and cryptophyte co-occurring with Dinophysis in the same planktonic assemblages.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frpro.2023.1308546</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frpro.2023.1308546</link>
        <title><![CDATA[Tracking down the rare ciliate biosphere]]></title>
        <pubdate>2024-01-08T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>James Weiss</author><author>Genoveva F. Esteban</author>
        <description><![CDATA[In protists, rare species include dormant organisms and those that do not reach high population abundance, and therefore, are not detected in the samples.  These rare microorganisms are part of the so-called ‘rare microbial biosphere’.  Although some may occasionally become abundant or dominant under particular environmental conditions, others do have a very rare occurrence, characterized by always having very low populations. The rare protist biosphere represents a significant component of microbial communities, and it is crucial for maintaining ecosystem biodiversity and function. In this study, we aim to demonstrate the richness of the rare ciliate biosphere and hypothesize on the reasons of rarity by combining morphological and ecological details on some exceedingly rare ciliates. The study includes the first report of different morphotypes of Dactylochlamys since 1928, first report of Penardiella undulata since 1930, second report of Penardiella interrupta since 1930, and an undescribed Penardiella species. The first report of Bryophyllum caudatum since 1933, microscopical observations and taxonomical discussion of the rare Legendrea bellerophon and of and undescribed Legendrea species. A new Apertospathula sp. with prokaryotic endosymbionts is described. The rarity of these species is explored and explained by their anaerobic metabolism combined with their prey selection.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/frpro.2023.1293531</guid>
        <link>https://www.frontiersin.org/articles/10.3389/frpro.2023.1293531</link>
        <title><![CDATA[Method of preparing unfixed ciliates for scanning electron microscopy without noticeable artifacts]]></title>
        <pubdate>2023-11-07T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Hideki Ishida</author><author>Kousei Yamamoto</author><author>Yuki Yano</author><author>Kenichi Ikeda</author><author>Liudmyla Gaponova</author><author>Rina Higuchi</author><author>Andrii Kolosiuk</author><author>Toshinobu Suzaki</author>
        <description><![CDATA[Water freeze-drying of biological samples has long been considered unfeasible as a sample preparation method for scanning electron microscopy (SEM) owing to the formation of damaging ice crystals. Contrary to this assumption, however, when live ciliates in water were frozen in contact with pre-cooled copper blocks in this study, they could be freeze-dried without artifact formation, although the success rate was only about 10%. This method offers several advantages over the traditional approach of chemical fixation followed by dehydration and drying. First, the degree of sample shrinkage associated with sample preparation was much lower than with chemical fixation. Second, contractile ciliates such as Spirostomum and Lacrymaria could be sampled in their elongated state, and the metachronal waves of cilia on the cell surface were well preserved. Moreover, this method requires no special equipment and only a few hours at most for sample preparation before SEM observation. Thus, although this method needs to be improved to increase the success rate in the future, it can be used to prepare samples for SEM observation that could not be prepared by other methods.]]></description>
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