Ciliate Genus Research Articles

Going down the rabbit hole: insight into the future of Paramecium (Ciliophora, Protista) biodiversity surveys

Paramecium, a research subject in many areas of life sciences, appeared to be a ciliate genus with a well known biodiversity structure. However, the understanding of its biological diversity has been evolving rapidly in recent years, driven by the discovery of new taxa and an expanded knowledge of the distribution of known species. Most future insights into Paramecium biodiversity are expected to come from molecular data, particularly through eDNA sampling. As one of the most recognisable microeukaryotes, commonly found in freshwater ecosystems, and with over a century of biodiversity research – including extensive reference data from GenBank records and living culture collections – Paramecium holds significant potential to become a model ciliate for studies in biodiversity and biogeography. This review addresses the challenges of species identification within the Paramecium genus, the current state of knowledge on its biodiversity and other factors that may shape future research. Despite some existing bottlenecks, new approaches to data acquisition and analysis will enable researchers to integrate diverse lines of evidence, allowing for exceptional explorations of Paramecium species and populations.

Assessing the effects of salinity on microbial communities and pollutant removal in urban wastewater treatment plants

This study assessed the impact of electrical conductivity (EC) on the microeukaryotic community and pollutant removal efficiency in full-scale wastewater treatment plants (WWTPs) in Catalonia, Spain. Monthly samples from seven WWTPs (2010−2021) were collected, with microbial communities identified by microscopy and effluent quality parameters measured. Linear mixed-effects models (LMER), indicator species analysis (IndVal), and structural equation modeling (SEM) were used to evaluate the effects of EC on WWTP operation and microbial communities. EC levels varied widely among WWTPs (800 to 15,000 μS cm−1), with mean removal rates generally low, not exceeding 26 %. EC removal was inversely correlated with organic matter removal (p < 0.05). IndVal analysis revealed distinct microbial communities associated with each WWTPs along the EC gradient (e.g., Beggiatoa spp. and Epistylis sp. were associated with high and low EC, respectively). High EC and peaks negatively affected the abundance of certain microorganisms (e.g., Acineria uncinata) (p < 0.05). Ciliate genera were most affected by EC peaks, with different species showing different salinity tolerance ranges (e.g. Holophyra discolor was affected by EC > 3000 μS cm-1). Seasonal variations did not significantly alter community sensitivity to salinity (p > 0.05). LMER and SEM analyses revealed strong adverse effects of high EC and EC peaks on microbial diversity, richness, and the efficiency of organic matter and TKN removal (p < 0.05). This highlights the importance of monitoring and controlling EC levels in WWTP influent to maintain optimal treatment performance and the need for effective technologies or biological processes to mitigate saline discharges into rivers.

Coleps shanghaiensis n. sp. challenges the validity of the genus Levicoleps (Ciliophora, Prostomatida)

Coleps is a common genus of pelagic ciliates in freshwater and brackish water habitats. Classification and phylogeny of Coleps species are, however, still full of confusion. In this study, we investigated Coleps shanghaiensis n. sp., collected from a river in Shanghai, China, by living observation, protargol staining, and molecular methods. Coleps shanghaiensis is about 70–90 µm × 35–55 µm in size, has a barrel-shaped body with three posterior spines, and possesses 21–24 ciliary rows, each composed of two perioral dikinetids and 19–22 monokinetids, and six caudal cilia. In SSU rRNA gene phylogenies, C. shanghaiensis fell within the clade of subspecies of Levicoleps biwae, which questions the validity of the genus Levicoleps. Furthermore, the biogeography of the genus Coleps is discussed.

Phylogeny and species delimitation of ciliates in the genus Spirostomum (Class, Heterotrichea) using single-cell transcriptomes.

Ciliates are single-celled microbial eukaryotes that diverged from other eukaryotic lineages over a billion years ago. The extensive evolutionary timespan of ciliate has led to enormous genetic and phenotypic changes, contributing significantly to their high level of diversity. Recent analyses based on molecular data have revealed numerous cases of cryptic species complexes in different ciliate lineages, demonstrating the need for a robust approach to delimit species boundaries and elucidate phylogenetic relationships. Heterotrich ciliate species of the genus Spirostomum are abundant in freshwater and brackish environments and are commonly used as biological indicators for assessing water quality. However, some Spirostomum species are difficult to identify due to a lack of distinguishable morphological characteristics, and the existence of cryptic species in this genus remains largely unexplored. Previous phylogenetic studies have focused on only a few loci, namely the ribosomal RNA genes, alpha-tubulin, and mitochondrial CO1. In this study, we obtained single-cell transcriptome of 25 Spirostomum species populations (representing six morphospecies) sampled from South Korea and the USA, and used concatenation- and coalescent-based methods for species tree inference and delimitation. Phylogenomic analysis of 37 Spirostomum populations and 265 protein-coding genes provided a robustious insight into the evolutionary relationships among Spirostomum species and confirmed that species with moniliform and compact macronucleus each form a distinct monophyletic lineage. Furthermore, the multispecies coalescent (MSC) model suggests that there are at least nine cryptic species in the Spirostomum genus, three in S. minus, two in S. ambiguum, S. subtilis, and S. teres each. Overall, our fine sampling of closely related Spirostomum populations and wide scRNA-seq allowed us to demonstrate the hidden crypticity of species within the genus Spirostomum, and to resolve and provide much stronger support than hitherto to the phylogeny of this important ciliate genus.

New geographical records and molecular investigation of the ciliate Spirostomum

Spirostomum is a genus of large ciliates, and its species are distributed worldwide. However, there has been limited research conducted on their geographical distribution and genomics. We obtained nine samples of ciliates from eight regions in Liaoning Province, China, and conducted a study on their geographical distribution and characteristics. Morphological and second-generation high-throughput sequencing methods were applied to identify the species, and a phylogenetic tree was established to gain a deeper understanding of the geographical distribution and evolutionary relationships of Spirostomum in Northeast China. The results identified Spirostomum yagiui and Spirostomum subtilis as a newly recorded species in Northeast China region. There are now five species of Spirostomum that have been recorded in China, and new details on the genomic characteristics of Spirostomum yagiui were provided. In addition, this study also identified the main branches of Spirostomum teres and Spirostomum minus in northern China, and provided a theoretical basis for the existence of hidden species. Spirostomum yagiui is the first species in the family Spirostomidae to have undergone mitochondrial genome sequencing.

Ontogeny and phylogeny of the anaerobic genus Urostomides with supplementing morphological characterization of the type and one little-known species (Alveolata: Ciliophora: Armophorea)

Abstract Urostomides is an obligate anaerobic ciliate genus in the family Apometopidae (Metopida). Although most congeners have been described using modern criteria, detailed ontogenetic data for both the family and genus have not been reported yet. In this study, we investigate the morphogenesis of two Urostomides species, viz., U. minimus (Kahl, 1927) comb. nov. and U. striatus (type species) in detail. Our findings reveal that the process closely resembles that of several described Metopidae species, except for a notable difference in the origin of the new adoral membranelles either from all perizonal rows or from other somatic kineties. Additionally, the data of U. minimus on the ciliature and SSU rRNA gene sequence are provided and those of U. striatus are supplemented based on Chinese isolates. We show the diplostichomonad morphology of the paroral membrane, a feature not previously observed in Urostomides species. Furthermore, our phylogenetic analyses confirm the monophyly of Urostomides.

New contributions to the taxonomy and phylogeny of the ciliate genus Pleuronema (Ciliophora, Scuticociliatia), with descriptions of two new species collected from the subtropical coastal wetlands in China

Ciliates of the genus Pleuronema are a speciose and ubiquitous group. Recent studies suggest that there may be a sizable amount of undiscovered species diversity. In the present study, two new Pleuronema species have been isolated from the subtropical coastal waters of China and characterized using morphological and taxonomical methods: Pleuronema pulchra n. sp. is characterized by a body size of 75–90 × 25–40 µm in vivo, 32–48 somatic kineties, four to seven preoral kineties, somatic kinety 1 composed of about 80 kinetids, and membranelle 2a with a single-rowed mid-portion and hook-like posterior portion. Pleuronema warreni n. sp. is defined by a body size of 55–80 × 25–45 µm in vivo, 35–42 somatic kineties, three to six preoral kineties, somatic kinety 1 with approximately 75 kinetids, and a mid-portion of membranelle 2a that is single-rowed and extremely long (occupying &amp;gt; 75% length of M2a). The phylogenetic analysis of the small subunit ribosomal RNA genes of Pleuronema members, including those of the two novel species, shows that the genus Pleuronema is a polyphyletic group. Both new species form a cluster with Pleuronema binucleatum KT033424, P. elegans KF840518, and “P. coronatum” JX310014 (identification to be verified). Additionally, we provide an illustrated key for 20 “coronatum-type” Pleuronema species, including the two new ones.

Paramecium Genetics, Genomics, and Evolution.

The ciliate genus Paramecium served as one of the first model systems in microbial eukaryotic genetics, contributing much to the early understanding of phenomena as diverse as genome rearrangement, cryptic speciation, cytoplasmic inheritance, and endosymbiosis, as well as more recently to the evolution of mating types, introns, and roles of small RNAs in DNA processing. Substantial progress has recently been made in the area of comparative and population genomics. Paramecium species combine some of the lowest known mutation rates with some of the largest known effective populations, along with likely very high recombination rates, thereby harboring a population-genetic environment that promotes an exceptionally efficient capacity for selection. As a consequence, the genomes are extraordinarily streamlined, with very small intergenic regions combined with small numbers of tiny introns. The subject of the bulk of Paramecium research, the ancient Paramecium aurelia species complex, is descended from two whole-genome duplication events that retain high degrees of synteny, thereby providing an exceptional platform for studying the fates of duplicate genes. Despite having a common ancestor dating to several hundred million years ago, the known descendant species are morphologically indistinguishable, raising significant questions about the common view that gene duplications lead to the origins of evolutionary novelties.

A new contribution to the raptorial ciliate genus Lacrymaria (Protista: Ciliophora): a brief review and comprehensive descriptions of two new species from Changjiang Estuary.

Ciliates serve as excellent indicators for water quality monitoring. However, their utilization is hindered by various taxonomic confusions. The ciliate genus Lacrymaria Bory de Saint-Vincent, 1824 is commonly found in different aquatic habitats, but its taxonomy has been sparsely investigated using state-of-the-art methods. This study investigated two new Lacrymaria species from Nanhui Wetland, Shanghai, China, using living observation, protargol staining, and molecular phylogeny methods. Lacrymaria songi sp. nov. is 180-340 × 20-25 μm in size and possesses 12-16 somatic kineties, 1 terminal contractile vacuole, 2 macronuclear nodules, and 2 types of rod-shaped extrusomes. Lacrymaria dragescoi sp. nov. is distinguished from its congeners by its cell size of 210-400 × 25-35 μm, 14-17 somatic kineties, 1 terminal contractile vacuole, 1 macronucleus, and 2 types of rod-shaped extrusomes. Phylogenetic analyses based on SSU rRNA gene sequences indicate that Lacrymariidae is monophyletic but Lacrymaria is not. Additionally, a brief review of the genus Lacrymaria is provided in this study. We suggest that L. bulbosa Alekperov, 1984, L. lanceolata Kahl, 1930, and L. ovata Burkovsky, 1970 be removed from the genus and propose Phialina lanceolata nov. comb. and Phialina ovata nov. comb. for the latter two. ZooBank registration: Present work: urn:lsid:zoobank.org:pub:CDFB1EBD-80BD-4533-B391-CEE89F62EDC4 Lacrymaria songi sp. nov.: urn:lsid:zoobank.org:act:417E7C2D-DAEC-4711-90BB-64AB3CD2F7D5 Lacrymaria dragescoi sp. nov.: urn:lsid:zoobank.org:act:8778D6B0-1F2E-473C-BE19-3F685391A40D.

Deciphering phylogenetic relationships of and delimiting species boundaries within the controversial ciliate genus Conchophthirus using an integrative morpho-evo approach

The phylum Ciliophora (ciliates) comprises about 2600 symbiotic and over 5500 free-living species. The inclusion of symbiotic ciliates in phylogenetic analyses often challenges traditional classification frameworks due to their morphological adaptions to the symbiotic lifestyle. Conchophthirus is such a controversial obligate endocommensal genus whose affinities to other symbiotic and free-living scuticociliates are still poorly understood. Using uni- and multivariate morphometrics as well as 2D-based molecular and phylogenetic analyses, we attempted to test for the monophyly of Conchophthirus, study the boundaries of Conchophthirus species isolated from various bivalves at mesoscale, and reveal the phylogenetic relationships of Conchophthirus to other scuticociliates. Multidimensional analyses of morphometric and cell geometric data generated the same homogenous clusters, as did phylogenetic analyses based on 144 new sequences of two mitochondrial and five nuclear molecular markers. Conchophthirus is not closely related to ‘core’ scuticociliates represented by the orders Pleuronematida and Philasterida, as assumed in the past using morphological data. Nuclear and mitochondrial markers consistently showed the free-living Dexiotricha and the mouthless endosymbiotic Haptophrya to be the nearest relatives of Conchophthirus. These three highly morphologically and ecologically dissimilar genera represent an orphan clade from the early radiation of scuticociliates in molecular phylogenies.

Phylogeny of the anaerobic ciliate genus Sonderia (Protista: Ciliophora: Plagiopylea), including the description of three novel species and a brief revision of the genus.

Anaerobic protists in general, and ciliates in particular, are important components of anoxic or hypoxic environments, however, their diversity remains underestimated. Sonderia is a poorly studied genus that is distributed worldwide and is commonly found in anaerobic environments. In the present study, the taxonomy and phylogeny of three new species, namely Sonderia aposinuata sp. nov., Sonderia paramacrochilus sp. nov. and Sonderia steini sp. nov., collected from China, were investigated based on microscopic observations and SSU rRNA gene sequencing methods. Sonderia aposinuata sp. nov. is diagnosed mainly by having a relatively large body size, a crescent-shaped oral opening, numerous slender extrusomes, one suture on the ventral side and two on the dorsal side, and a buccal cavity that occupies the anterior third of the cell. Sonderia paramacrochilus sp. nov. closely resembles S. macrochilus but differs mainly by its oral opening being located closer to the anterior cell margin and its spindle-shaped extrusomes. Sonderia steini sp. nov. is a freshwater species that can be recognized by its shallow buccal cavity, sparsely distributed rod-shaped extrusomes, and having 68-79 monokinetidal somatic kineties that form sutures on both sides of the body. Phylogenetic analyses based on small subunit ribosomal RNA (SSU rRNA) gene sequence data support the monophyly of the family Sonderiidae, however, Sonderia is paraphyletic. The genus Sonderia is briefly revised and a key to the identification of species belonging to this genus is supplied.

Inclusion of the aerial part and condensed tannin extract from Cistus ladanifer L. in lamb diets – Effects on rumen microbial community and fatty acid profile

This study was carried out to test the hypothesis that the inclusion of condensed tannins (CT) from Cistus ladanifer aerial part or extract in a diet composed of dehydrated lucerne and supplemented with 60 g/kg of soybean oil can modulate the rumen microbiome and increase the production of healthy biohydrogenation intermediates (BI). Hence, thirty-six lambs were used to evaluate the effect of 3 levels of C. ladanifer CT (0 %, 1.25 % and 2.5 % of CT) and two ways of CT supply (C. ladanifer aerial parts and C. ladanifer CT extract) on rumen fatty acids and volatile fatty acids profile and ciliate protozoa and bacteria community composition. The experiment lasted 35 days, and rumen samples were collected immediately after slaughter. Ciliate protozoa were analyzed by microscopic counting, and high-throughput 16 S rRNA gene sequencing was used to analyse rumen bacterial composition. Condensed tannins diets did not affect ruminal fermentation. The inclusion of C. ladanifer aerial part or extract in lamb diets did not increase the t11–18:1 in the rumen content. On the other hand, the t11–18:1 proportion was lower in the rumen of lambs fed both C. ladanifer diets and the highest level of extract diet when compared with the lowest level of extract diet and the diets without CT inclusion. Regarding the rumen microbiome, the total of ciliates was not influenced by the CT level in diets but decreased with the inclusion of C. ladanifer aerial part in the diet. Entodinium genus was strongly and positively related with both total BI and t11–18:1 and it also was the ciliate genus most negatively related with rumen estimate biohydrogenation (BH) completeness. Independently of the diets, the bacterial community of rumen content was dominated by Firmicutes (49.8 %) and Bacteroidetes (30.8 %) phyla. The Lachnobacterium was the genus most closely related with t11–18:1 and negatively related with 18:0 and BH completeness, which suggests that the Lachnobacterium plays an important role on the BH when diets without CT inclusion and lower dose of C. ladanifer extract was fed to lambs, being responsible for t11–18:1 ruminal production. Cistus ladanifer aerial part and extract influenced the ruminal microbial composition, but at the conditions used, the increase in the ruminal production of healthy BI was not observed, highlighting the inconsistent BH response to dietary CT and underlining the need to develop efforts to increase knowledge about this CT source and its interactions with other feed factors and with the ruminal microbial community.

Rumen ciliates (Alveolata, Ciliophora) associated with goats: checklist, geographic distribution, host specificity, phylogeny and molecular dating.

Although the diversity (~35 species) and worldwide distribution of goats (Ruminantia, Bovidae, Caprinae) are significant, studies on the diversity of symbiont ciliates in these mammals are scarce in comparison to other ruminants. The present work is a review and checklist of species based on taxonomic, morphologic, and ecologic studies of rumen ciliate protozoa in goats, presenting geographic distribution and hosts, as well as estimating the macroevolutionary relationships of the species observed in the studies. To that end, all of the available literature on databases was reviewed, the schematic drawings were made based on information present in the original description of the taxa, and the phylogenetic relationships were inferred based on Maximum Likelihood and Bayesian Inference analyses. According to our review, 72 species and 14 genera of ciliates have been associated with goats. Through the analysis of the association between ciliate genera and caprine hosts, it was shown that ciliates are more associated with domestic animals (Capra hircus14 genera) than wild ones (Rupicapra rupicaprasix genera, Capra ibexone genus, Capra pyrenaicaone genus). Thirteen countries were identified in the distribution map as having had reports of ciliate species associated with goats. The interaction networks of ciliates and their hosts showed that the species of ciliates associated with goats also occur in other herbivore mammal species. The recovered phylogenetic hypotheses show that the ciliate species in goats form a non-monophyletic group with maximum and minimum ages of ~8.2My and ~2.4My. We have also found that a large portion of the studies on the diversity of ciliates in goats does not employ all necessary techniques in an integrative way, despite it being essential for detailed descriptions and better knowledge of this fraction of biodiversity.

Taxonomy and molecular phylogeny of two poorly known ciliate genera, Balantidion and Acropisthium (Protista: Ciliophora: Litostomatea), including a new species of Balantidion

The class Litostomatea Small & Lynn, 1981 is a morphologically diverse ciliate group including hundreds of free-living and endocommensal species. The genera Acropisthium Perty, 1852 and Balantidion Eberhard, 1862 previously consisted of one free-living freshwater species each. Here, we not only highlight additional morphological features of the two type species, but also investigate a new species, Balantidion foissneri sp. nov., isolated from a river flowing through Lake Weishan, China, based on complementary methods, i.e., living morphology, stained preparations, and 18S rRNA gene sequence data. Balantidion foissneri sp. nov. can be distinguished from the type species, B. pellucidum Eberhard, 1862, by the body size (115–170 × 50–80 μm vs. 70–100 × 25–45 μm in B. pellucidum), oral bulge (distinct vs. indistinct), extrusome shape (filiform vs. rod-shaped), and the number of somatic kineties (46–60 vs. 25–40). In Balantidion species, pre-encystment trophonts show similarly-shaped polymorphic cytoplasmic lepidosomes destined to adorn the outer surface of the resting cyst. Based on the current knowledge, assignment of Balantidion to the family Acropisthiidae Foissner & Foissner, 1988 is proposed. In addition, phylogenetic analyses based on molecular data show that the two Balantidion species form a fully-supported clade to which Acropisthium mutabile has a sister relationship.

Diversity and Phylogenetic Position of Bothrostoma Stokes, 1887 (Ciliophora: Metopida), with Description of Four New Species

Bothrostoma is a genus of anaerobic ciliates in family Metopidae comprising four species, all described based solely on the morphology of living and fixed cells. Unlike other metopids, cells of Bothrostoma are not twisted anteriorly, have a flattened preoral dome, a very prominent sail-like paroral membrane, and an adoral zone of distinctive, very narrow, curved membranelles confined to a wide, non-spiraling peristome on the ventral side. We examined 20 populations of Bothrostoma from hypoxic freshwater sediments. We provide morphological characterization and 18S rRNA gene sequences of four new species, namely B. bimicronucleatum sp. nov., B. boreale sp. nov., B. kovalyovi sp. nov., and B. robustum sp. nov., as well as B. undulans (type species), B. nasutum, and B. ovale comb. nov. (original combination Metopus undulans var. ovalis Kahl, 1932). Except for B. nasutum, Bothrostoma species show low genetic variability among geographically distant populations. Intraspecific phenotypic variability might be driven by environmental conditions. In phylogenetic analyses, Bothrostoma is not closely related to Metopus sensu stricto and forms a moderately supported clade with Planometopus, here referred to as BoPl clade. The anterior axial torsion of the body, typical of other Metopidae, appears to have been lost in the last common ancestor of the BoPl clade.

Integrative studies on the taxonomy and molecular phylogeny of four new Pleuronema species (Protozoa, Ciliophora, Scuticociliatia)

The ciliate genus Pleuronema comprises approximately 30 nominal species and has been reported in freshwater, brackish water, and marine habitats. Nevertheless, recent studies have indicated that there might be a large undiscovered species diversity. In the present work, four new Pleuronema species, namely P. foissneri sp. nov., P. parasmalli sp. nov., P. parasalmastra sp. nov., and P. paraorientale sp. nov., collected from Shenzhen, southern China, was investigated using taxonomic methods. The diagnosis, description, comparisons with morphologically related species and detailed morphometric data are supplied for each. The small subunit ribosomal RNA (SSU rRNA) gene of the four new species is sequenced and their molecular phylogeny is analyzed. The SSU rRNA gene tree shows that Pleuronema is polyphyletic comprising several separate clades. All four new species cluster consistently with P. orientale KF206429, P. puytoraci KF840520 and P. setigerum FJ848874 within the core Pleuronematidae + Peniculistomatidae clade. Phylogenies of Pleuronematidae-related taxa are also discussed.

A new contribution to the taxonomy and phylogeny of the ciliate genus Spirostomum (Alveolata, Ciliophora, Heterotrichea), with comprehensive descriptions of two species from wetlands in China

Species of the ciliate genus Spirostomum Ehrenberg, 1834 are distributed worldwide and have a research history spanning more than two centuries. However, species delimitation and phylogenetic relationships within this genus are still uncertain due to the paucity of stable morphologic characters for species separation and the unavailability of accompanying morphological data for most molecular sequences in public databases. In the present study, S. yagiui Shigenaka, 1959 (three populations) and S. caudatum (Müller, 1786) Delphy, 1939 (one population) were investigated using morphological and molecular methods for the first time in China. Detailed morphological data for the two species were documented, and improved diagnoses were supplied based on a combination of previous studies and the current work. It should be highlighted that there were three different atypical morphotypes identified in a Ningbo population of S. yagiui which may represent various stages in conjugative reproduction. Molecular phylogenies based on 18S, ITS1-5.8S-ITS2, and 28S rRNA gene sequences show that the genus Spirostomum is monophyletic, however, the internal relationships inferred from different genes were poorly resolved but suggest that the species with a moniliform macronucleus comprise an early-diverging clade within this genus. Finally, the global distribution of Spirostomum is summarized based on previous and present studies.

Morphological and phylogenetic investigations shed light on evolutionary relationships of the enigmatic genus Copemetopus (Ciliophora, Alveolata), with the proposal of Copemetopus verae sp. nov.

Copemetopus Villeneuve-Brachon, 1940 is a rare, poorly known sapropelic ciliate genus composed of only two valid nominal species. Over time, Copemetopus was taxonomically assigned to Heterotrichea and Armophorea classes, but its phylogenetic affinities remained unknown. Until the present study, there were no molecular data available for Copemetopus representatives. Here, we present the 18S and 28S-rDNA sequences and the phylogenetic position of Copemetopus verae sp. nov., as well as its detailed morphological description based on live observations, protargol impregnation, and scanning electron microscopy. Transmission electron micrographs of the type species C. subsalsus Villeneuve-Brachon, 1940 reveal new morphological traits and a unique somatic ciliature pattern of Copemetopus, composed by short segments of dikinetids with one or two supplementary kinetosomes. The phylogenetic trees recovered Copemetopus as the sister group of the genus Protocruzia, both constituting early-divergent lineages that split first from a common ancestor of Intramacronucleta. Morphological and molecular evidence suggest that Copemetopus is neither a heterotrichean nor an armophorean ciliate, but a distinct clade related to Protocruzia.

Molecular Data Reveal a Cryptic Diversity in the Genus Urotricha (Alveolata, Ciliophora, Prostomatida), a Key Player in Freshwater Lakes, With Remarks on Morphology, Food Preferences, and Distribution.

Species of the ciliate genus Urotricha are key players in freshwater plankton communities. In the pelagial of lakes, about 20 urotrich species occur throughout an annual cycle, some of which play a pivotal role in aquatic food webs. For example, during the phytoplankton spring bloom, they consume a remarkable proportion of the algal production. In ecological studies, urotrich ciliates are usually merely identified to genus rank and grouped into size classes. This is unsatisfying considering the distinct autecological properties of individual species and their specific spatial and temporal distribution patterns. As a basis for future research, we characterized in detail four common urotrich morphotypes, i.e., specimens identified as U. furcata and tentatively as U. agilis, U. pseudofurcata, and U. castalia, using state-of-the-art methods. We used an integrative polyphasic approach, in which morphological studies (in vivo observation, silver staining methods, scanning electron microscopy) were linked with a molecular approach exploiting four different gene fragments as taxonomic DNA barcodes with different resolution potential (SSU rDNA, ITS-1, ITS-2, hypervariable V4 and V9 regions of the SSU rDNA). We shed light on the diversity of urotrich ciliates as well as on their global distribution patterns, and annual cycles. Additionally, we coupled individual species occurrences and environmental parameters, and subsequently modeled the distribution and occurrence, using logistic regressions. Furthermore, for one strain putatively identified as U. castalia, we ascertained the optimal cultivation media and food preferences. Thereby, our comprehensive view on these important freshwater ciliates that frequently occur in environmental high throughput sequencing datasets worldwide will allow future studies to better exploit protistan plankton data from lakes.

A Case Study of the Morphological and Molecular Variation within a Ciliate Genus: Taxonomic Descriptions of Three Dysteria Species (Ciliophora, Cyrtophoria), with the Establishment of a New Species

Three Dysteria species, D. crassipes Claparède & Lachmann, 1859; D. brasiliensis Faria et al., 1922; and D. paracrassipes n. sp., were collected from subtropical coastal waters of the East China Sea, near Ningbo, China. The three species were studied based on their living morphology, infraciliature, and molecular data. The new species D. paracrassipes n. sp. is very similar to D. crassipes in most morphological features except the preoral kinety, which is double-rowed in the new species (vs. single-rowed in D. crassipes). The difference in the small ribosomal subunit sequences (SSU rDNA) between these two species is 56 bases, supporting the establishment of the new species. The Ningbo population of D. crassipes is highly similar in morphology to other known populations. Nevertheless, the SSU rDNA sequences of these populations are very different, indicating high genetic diversity and potentially cryptic species. Dysteria brasiliensis is cosmopolitan with many described populations worldwide and four deposited SSU rDNA sequences. The present work supplies morphological and molecular information from five subtropical populations of D. brasiliensis that bear identical molecular sequences but show significant morphological differences. The findings of this study provide an opportunity to improve understanding of the morphological and genetic diversity of ciliates.