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Plankton ecologists ultimately focus on forecasting, both applied and environmental outcomes. We review how appreciating planktonic ciliates has become central to these predictions. We explore the 350‐year‐old canon on planktonic ciliates and examine its steady progression, which has been punctuated by conceptual insights and technological breakthroughs. By reflecting on this process, we offer suggestions as to where future leaps are needed, with an emphasis on predicting outcomes of global warming. We conclude that in terms of climate change research: (i) climatic hotspots (e.g. polar oceans) require attention; (ii) simply adding ciliate measurements to zooplankton/phytoplankton‐based sampling programs is inappropriate; (iii) elucidating the rare biosphere's functional ecology requires culture‐independent genetic methods; (iv) evaluating genetic adaptation (microevolution) and population composition shifts is required; (v) contrasting marine and freshwaters needs attention; (vi) mixotrophy needs attention; (vii) laboratory and field studies must couple automated measurements and molecular assessment of functional gene expression; (viii) ciliate trophic diversity requires appreciation; and (ix) marrying gene expression and function, coupled with climate change scenarios is needed. In short, continued academic efforts and financial support are essential to achieve the above; these will lead to understanding how ciliates will respond to climate change, providing tools for forecasting. [ABSTRACT FROM AUTHOR]

Species of Acanthamoeba were first described using morphological characters including cyst structure and cytology of nuclear division. More than 20 nominal species were proposed using these methods. Morphology, especially cyst shape and size, has proven to be plastic and dependent upon culture conditions. The DNA sequence of the nuclear small-subunit (18S) rRNA, the Rns gene, has become the most widely accepted method for rapid diagnosis and classification of Acanthamoeba. The Byers-Fuerst lab first proposed an Rns typing system in 1996. Subsequent refinements, with an increasing DNA database and analysis of diagnostic fragments within the gene, have become widely accepted by the Acanthamoeba research community. The development of the typing system, including its current state of implementation is illustrated by three cases: (i) the division between sequence types T13 and T16; (ii) the diversity within sequence supertype T2/T6, and (iii) verification of a new sequence type, designated T20. Molecular studies make clear the disconnection between phylogenetic relatedness and species names, as applied for the genus Acanthamoeba. Future reconciliation of genetic types with species names must become a priority, but the possible shortcomings of the use of a single gene when reconstructing the evolutionary history of the acanthamoebidae must also be resolved. [ABSTRACT FROM AUTHOR]

It is remarkable, that apart from his printed legacy, Richard left behind also a pictorial legacy by creating in 2006 the extraordinary website " I Paramecium i and Other Ciliates: Richard Allen's Image Collection" (https://www..pbrc.hawaii.edu/allen/). Thereby, some parts of the membrane are rescued by partial retrieval (as discoidal vesicles) from the discharging food vacuole and used for the formation of a new food vacuole at the cytostome (Allen & Fok, [6]; Fok & Allen, [12], [13]). Aside from that, he was repeatedly invited to contribute articles for review organs, for example, I International Review of Cytology i (Allen & Fok, [6]; Allen & Naitoh, [8]; Fok & Allen, [12]), I Cell Biology International i (Tani et al., [21]), and chapters for monographs, for example, I Membrane Fusion i (Allen, [2]), I Paramecium i (Allen, [3]), I Advances in Cell and Molecular Biology of Membranes i (Allen & Fok, [5]; Fok & Allen, [13]), I Osmotic and Ionic Regulation: Cells and Animals i (Allen et al., [10]) and I Methods in Cell Biology i (Hausmann & Allen, [18]). Richard Dean Allen passed away on February 10, 2023, in Honolulu, Oahu, Hawaii, the United States. [Extracted from the article]

This study reports the first record of Sorosphaerula radicalis (Phytomyxea, Rhizaria) in continental Europe (Tirol, Austria) and provides first molecular data for this species. An 18S rRNA phylogeny placed S. radicalis into the Plasmodiophorida, although distant from other members of the genus Sorosphaerula and close to the parasite of water cress Hillenburgia nasturtii. To resolve this polyphyly, we compare morphological data and life cycles of Sorosphaerula veronicae (the type species of the genus Sorosphaerula), Hillenburgia nasturtii, and Sorosphaerula radicalis. We conclude that Sorosphaerula radicalis belongs to the recently established genus Hillenburgia. [ABSTRACT FROM AUTHOR]

Monocercomonoides is a genus of anaerobic flagellates found mainly in the gut of insects and vertebrates. We explored the ploidy of six strains of Monocercomonoides using fluorescence in situ hybridization (FISH) with probes against the SufDSU gene known to be in a single copy in M. exilis. Our results show that all investigated strains are haploid, with a single clear signal displayed in most of the analyzed nuclei. Staining of the telomeric repeats TTAGGG using FISH revealed that all investigated strains, except for strains of M. merkovicensis, exhibit a similar number of telomeric signals to those of M. exilis. DNA content of the nuclei in seven strains was assessed using flow cytometry. With the knowledge of the ploidy, their haploid genome sizes were estimated to vary from 60 to 161 Mbp. The genome size variation observed in Monocercomonoides is much larger than the variation within other genera of metamonads such as Trichomonas, Tritrichomonas, or Giardia, but similar to the variations observed within genera of algae or plants. [ABSTRACT FROM AUTHOR]

Protists in the phylum Ciliophora possess a complex membrane‐trafficking system, including osmoregulatory Contractile Vacuoles and specialized secretory organelles. Molecular cell biological investigations in Tetrahymena thermophila have identified components of the protein machinery associated with the secretory organelles, mucocysts. The Qa‐SNARE Syn7lp plays a role in mucocyst biogenesis as do subunits of the CORVET tethering complex (specifically Vps8). Indeed, Tetrahymena thermophila possesses expanded gene complements of several CORVET components, including Vps33 which is also a Sec1/Munc18 (SM) protein that binds Qa‐SNAREs. Moreover, the Qa‐SNAREs in Paramecium tetraurelia have been localized to various endomembrane organelles. Here, we use comparative genomics and phylogenetics to determine the evolutionary history of the SM and Qa‐SNARE proteins across the Ciliophora. We identify that the last ciliate common ancestor possessed the four SM proteins and six Qa‐SNAREs common to eukaryotes, including the uncommonly retained Syntaxin 17. We furthermore identify independent expansion of these protein families in several ciliate classes, including concurrent expansions of the SM protein‐Qa SNARE partners Sec1:SynPM in the oligohymenophorean ciliates lineage, consistent with novel Contractile Vacuole specific innovations. Overall, these data are consistent with SM proteins and Qa‐SNAREs being a common set of components for endomembrane modulation in the ciliates. [ABSTRACT FROM AUTHOR]

The family Ophryoscolecidae currently comprises 225 species of trichostomatid ciliates, subdivided into three subfamilies (Entodiniinae, Diplodiniinae, and Ophryoscolecinae). The last taxonomic review of the family was performed 55 years ago, but recent morphological and molecular studies indicate the need for a profound review of the systematics of this taxon, since its current taxonomy is insufficient to organize the diversity of the group. Here, we briefly review the systematics of the family Ophryoscolecidae based on information recovered from the literature and new morphological and molecular data. We add four new 18S rDNA sequences of ophryoscolecids to molecular databases, which contributed to improving the comprehension of intrafamily relationships within this group. Finally, we discuss some systematic problems and suggest approaches to resolve such inconsistencies in the future. [ABSTRACT FROM AUTHOR]

Foraminifera include diverse shell‐building lineages found in a wide array of aquatic habitats from the deep‐sea to intertidal zones to brackish and freshwater ecosystems. Recent estimates of morphological and molecular foraminifera diversity have increased the knowledge of foraminiferal diversity, which is critical as these lineages are used as bioindicators of past and present environmental perturbation. However, a comparative analysis of foraminiferal biodiversity between their major habitats (freshwater, brackish, intertidal, and marine) is underexplored, particularly using molecular tools. Here, we present a metabarcoding survey of foraminiferal diversity across different ecosystems using newly designed foraminifera‐specific primers that target the hypervariable regions of the foraminifera SSU‐rRNA gene (~250–300 bp long). We tested these primer sets on four foraminifera species and then across several environments: the intertidal zone, coastal ecosystems, and freshwater vernal pools. We retrieved 655 operational taxonomic units (OTUs); the majority of which are undetermined taxa that have no closely matching sequences in the reference database. Furthermore, we identified 163 OTUs with distinct habitat preferences. Most of the observed OTUs belonged to lineages of single‐chambered foraminifera, including poorly explored freshwater foraminifera which encompass a clade of Reticulomyxa‐like forms. Our pilot study provides the community with an additional set of newly designed and taxon‐specific primers to elucidate foraminiferal diversity across different habitats. [ABSTRACT FROM AUTHOR]

Lagenophrys cochinensis is a peritrich ciliate originally reported as an ectocommensal of the wood-boring isopods Sphaeroma terebrans, Sphaeroma triste, and Sphaeroma annandalei and the tanaidacean Apseudes chilkensis in estuaries of southern India. In the present study, it was found to occur also on Sphaeroma quoyanum, Sphaeroma walkeri, and Exosphaeroma planulum. New material was used to make permanent preparations, allowing a comprehensive description of the morphology of L. cochinensis for the first time. The macronucleus of L. cochinensis was found to have an elongate shape that spans the width of the cell body, unlike the compact macronucleus originally described. In addition, the loricae of all samples examined were subcircular or shorter than wide, not longer than wide as originally described. Polykinetid 3 of the infundibular infraciliature consisted of three rows of kinetosomes, only the third species of Lagenophrys found to have more than two rows in polykinetid 3 so far. Samples of L. cochinensis on S. quoyanum from New Zealand and California appeared to represent a population distinct from others. The species has a cosmopolitan distribution, probably owing to the ease with which its hosts are transported from one estuary to another in drifting wood or on hulls of ships. [ABSTRACT FROM AUTHOR]

Blastocystis is an anaerobic intestinal protozoan parasite found in humans and many kinds of animals that mainly causes diarrhea, abdominal pain, and other clinical symptoms. At present, research on the prevalence and subtype diversity of Blastocystis in domestic pigeons is very limited. The purpose of this study was to detect the infection rate and gene subtype distribution of Blastocystis in domestic pigeons in Henan Province, Central China, to provide a foundation for preventing and controlling Blastocystis in domestic pigeons. Fecal DNA was extracted from 504 fresh fecal samples of pigeons collected from four areas in Henan Province, Central China. All DNA samples were investigated by polymerase chain reaction, and positive samples were sequenced to analyze the gene subtypes based on small ribosomal subunit (SSU rRNA) gene. The overall infection rate of Blastocystis in pigeons in Henan Province was 7.7% (39/504). Four subtypes (STs) of Blastocystis were identified including ST1 (2/39, 5.1%), ST3 (16/39, 41%), ST4 (1/39, 2.6%), and ST7 (20/39, 51.3%), all of which belonged to zoonotic subtypes, and ST7 was the dominant gene subtype. The results show that Blastocystis infection is common in domestic pigeons in Henan Province, Central China, and the pathogens were zoonotic subtypes. Particular attention should be given to reducing the risk of transmission of Blastocystis from domestic pigeons to humans. [ABSTRACT FROM AUTHOR]

A recent ultrastructural study on the tintinnid ciliate Schmidingerella meunieri displayed unique types of somatic kinetids. The dikinetids (paired basal bodies) have, besides kinetodesmal fibrils and transverse ribbons, some special features, that is, overlapping postciliary ribbons and three extraordinary microtubular ribbons, which together form a conspicuous network in the ciliated anterior cell portion. The distribution of this feature among tintinnids is studied in chemically fixed and ultrathin‐sectioned specimens from six genera and five families collected in European coastal waters. The taxa are scattered across the molecular tree. Actually, the somatic kinetids of these six genera share the special features discovered in S. meunieri. Accordingly, the overlapping postciliary ribbons and the three extraordinary ribbons were already present in the early stages of tintinnid evolution, namely in the last common ancestor of tintinnids with hard loricae. Owing to the lack of ultrastructural data in the basally branching Tintinnidiidae with their soft loricae and in aloricate choreotrichids other than the aberrant strobilidiids, the first appearance of the structures is still uncertain. The related oligotrichids do not possess overlapping postciliary ribbons, but show electron‐dense material at the sites where the ribbons I–III originate in tintinnids. None of these features is found in any other spirotrich ciliate. [ABSTRACT FROM AUTHOR]

This study provides a morphological, ultrastructural, and phylogenetic characterization of a novel micro‐eukaryotic parasite (2.3–2.6 µm) infecting amphipod genera Echinogammarus and Orchestia. Longitudinal studies across two years revealed that infection prevalence peaked in late April and May, reaching 64% in Echinogammarus sp. and 15% in Orchestia sp., but was seldom detected during the rest of the year. The parasite infected predominantly hemolymph, connective tissue, tegument, and gonad, although hepatopancreas and nervous tissue were affected in heavier infections, eliciting melanization and granuloma formation. Cell division occurred inside walled parasitic cysts, often within host hemocytes, resulting in hemolymph congestion. Small subunit (18S) rRNA gene phylogenies including related environmental sequences placed the novel parasite as a highly divergent lineage within Class Filasterea, which together with Choanoflagellatea represent the closest protistan relatives of Metazoa. We describe the new parasite as Txikispora philomaios n. sp. n. g., the first confirmed parasitic filasterean lineage, which otherwise comprises four free‐living flagellates and a rarely observed endosymbiont of snails. Lineage‐specific PCR probing of other hosts and surrounding environments only detected T. philomaios in the platyhelminth Procerodes sp. We expand the known diversity of Filasterea by targeted searches of metagenomic datasets, resulting in 13 previously unknown lineages from environmental samples. [ABSTRACT FROM AUTHOR]

Tintinnid ciliates build loricae, whose structure, shape, and size still largely represent the basis for taxonomy and classification, although genetic analyses demonstrated their limited utility for inferring evolutionary relationships. The textures of the lorica walls, however, result from the chemical and physical properties of the forming material, which is supposed to be rather conserved in closely related taxa, viz., congeners and confamilial genera. Within a particular texture, small deviations in the chemical composition might affect the wall's stickiness and accordingly its capability to adhere foreign particles, explaining the intertwining of tintinnids with hyaline and agglutinated loricae in phylogenetic inferences. In a comprehensive comparative study, the lorica textures were electron microscopically and morphometrically analyzed in 21 species from 17 genera and more than nine families together with literature data. Most species were investigated for the first time, and the taxa cover a substantial portion of the molecular genealogy. The phylogeny‐aware analysis of the lorica‐related features provides a preliminary hypothesis on lorica evolution. Eventually, this conspectus suggests the dominance of hard lorica walls with an alveolar texture and proposes different modes of lorica formation. [ABSTRACT FROM AUTHOR]

Presents an overview on the taxonomy and phylogeny of protists. Kinds of biotic interactions; Role of protists in support of all life on the planet Earth; Influence of protists in restricting bacterial and fungal growth in such habitats; Role of anoxic protists in altering Earth's environment chemically.

Highlights the important trends in the field of protistology. Controversy over the origin of the eukaryotic cells; Emergence of complete genome sequencing in the field of parasitology; Role of protists in global carbon and sulfur cycles.

Presents the study redescribing the sarcocysts of Sarcocystis rileyi (Apicomplexa: Sarcocystidae). Identification of the intermediate hosts for Sarcocystis rileyi; Assessment of the types of specimens for the study; Investigation of the sections of pectoral muscles.

Discusses the role of the Gregarine parasite Ascogregarina culicus in the maintenance of Chikungunya virus in vector mosquito. Vertical transmission of the virus; Vertical transmission of the virus through oocysts of the parasites.

Types and the corresponding rules in the International Code of Zoological Nomenclature are crucial for taxonomy and are meant to provide nomenclatural stability. In the case of neotypification, especially diligent taxonomic work is required to retain continuity. In the present communication, we first outline the main principles of typification and neotypification. We then discuss a critical case, using a current example from the marine planktonic tintinnid genus Tintinnopsis Stein, 1867 (Alveolata, Ciliophora). This diverse and ubiquitous genus is nonmonophyletic, but its revision and the erection of new related genera is currently prevented by the uncertain affiliation of its type species. [ABSTRACT FROM AUTHOR]

The vampyrellids (Vampyrellida, Rhizaria) are naked amoebae of considerable genetic diversity. Three families have been well‐defined (Vampyrellidae, Leptophryidae, and Placopodidae), but most vampyrellid lineages detected by environmental sequencing are poorly known or completely uncharacterized. In the brackish sediment of Lake Bras D'Or, Nova Scotia, Canada, we discovered an amoeba with a vampyrellid‐like life history that was morphologically dissimilar from previously known vampyrellid taxa. We established a culture of this amoeba, studied its feeding behavior and prey range specificity, and characterized it with molecular phylogenetic methods and light and electron microscopy. The amoeba was a generalist predator (i.e. eukaryotroph), devouring a range of marine microalgae, with a strong affinity for some benthic diatoms and Chroomonas. Interestingly, the amoeba varied its feeding strategy depending on the prey species. Small diatoms were engulfed whole, while larger species were fed on through extraction with an invading pseudopodium. The SSU rRNA gene phylogenies robustly placed the amoeba in the most basal, poorly described lineage ("clade C") of the Vampyrellida. Based on the phylogenetic position and the distinct morphology of the studied amoeba, we here describe it as Sericomyxa perlucida gen. et sp. nov., and establish the new vampyrellid family Sericomyxidae for "clade C." [ABSTRACT FROM AUTHOR]

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 μm 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. [ABSTRACT FROM AUTHOR]