Peter Vďačný

Comenius University Bratislava · Department of Zoology

Clevelandellids are highly diversified and widespread unicellular eukaryotic organisms inhabiting the digestive tract of a broad spectrum of invertebrates and vertebrates. Time‐calibrated phylogeny of clevelandellids was built to reconstruct their ancestral hosts using stochastic mapping, investigate their coevolution with animal hosts using an eve...

Ciliated protists are unicellular eukaryotic organisms characterized by their morphological diversity, ubiquitous distribution, and the important roles they play in a wide range of biological studies. The class Litostomatea is a morphologically diverse ciliate group that comprises hundreds of free-living and endosymbiotic species. Here, we sequence...

Specific ecological conditions in the high mountain environment exert a selective pressure that often leads to convergent trait evolution. Reticulations induced by incomplete lineage sorting and introgression can lead to discordant trait patterns among gene and species trees (hemiplasy/xenoplasy), providing a false illusion that the traits under st...

Heterolepidoderma is a widely distributed gastrotrich genus encompassing 22 freshwater and 15 marine species. In the present study, two new Heterolepidoderma and four new Heterolepidoderma-like species were discovered in the inland waters of Central Europe. Although Heterolepidoderma-like species exhibited all the morphological features typical of...

The ciliate order Clevelandellida unites endosymbionts of the digestive tract of a variety of invertebrates and vertebrates. In the present study, the primary and secondary structures of nuclear and hydrogenosomal rRNA molecules were employed to reconstruct the phylogenetic relationships and to estimate the divergence times of clevelandellids inhab...

The digestive tract of oligochaetes harbours a diverse ciliate community embracing plagiotomids, nyctotherids, astomes, and hysterocinetids. Although several hundred intestinal ciliate species are known, only two hysterocinetids have been reported from the intestine of Holarctic lumbricid earthworms hitherto. The present study is focused on the tax...

Although the river nerite Theodoxus fluviatilis (Gastropoda: Neritimorpha) has an exceptionally broad geographical and ecological distribution, it carries only four ciliate species: Hypocomella quatuor, Protospirella mazurica, Scyphidia sp., and Trichodina baltica. After more than a half-century gap, we re-discovered P. mazurica in a Danubian popul...

Organisms classified as members of the genus Paramecium belong to the best-known group of single-celled eukaryotes. Nevertheless, the phylogeny within the genus Paramecium has been discussed and revisited in recent decades and remains partly unresolved. By applying an RNA sequence-structure approach, we attempt to increase accuracy and robustness o...

Ciliates of the order Mobilida are obligate symbionts of a broad spectrum of invertebrates and vertebrates. Rigid structures of their adhesive disc, which serves for attachment to the host, are traditionally used for species identification. Using a holistic morpho-evo-eco approach, we attempted to address whether (1) also host organisms and their l...

Hybridization is an important evolutionary process that can fuel diversification via formation of hybrid species or can lead to fusion of previously separated lineages by forming highly diverse species complexes. We provide here the first molecular evidence of hybridization in wild populations of ciliates, a highly diverse group of free-living and...

Unlabelled: The morphology and molecular phylogeny of freshwater pleurostomatid ciliates are insufficiently explored. In the present study, we investigated three new Amphileptus species discovered in Lake Weishan and its vicinity, northern China, using standard alpha-taxonomic methods. Amphileptus paracarchesii sp. nov. is characterized by a later...

Hybridization is a key mechanism involved in lineage diversification and speciation, especially in ecosystems that experienced repeated environmental oscillations. Recently radiated plant groups, which have evolved in mountain ecosystems impacted by historical climate change provide an excellent model system for studying the impact of gene flow on...

The subgenus Hystricochaetonotus Schwank, 1990 is one of the most species-rich subgenera of Chaetonotus Ehrenberg, 1830. It has a worldwide distribution and encompasses 37 species predominantly living in the benthos and periphyton of limnetic habitats. We have discovered further nine new species in running and stagnant waters in Slovakia (Central E...

The histophagous ciliate Tetrahymena rostrata (Kahl, 1926) is a facultative parasite of the renal organ of land snails and slugs. The possibility of transovum transmission and the lack of heteroparental sex make T. rostrata an interesting model for studying host specificity and distribution patterns in pathogenic ciliates. We recorded mass Tetrahym...

Like many other aquatic animals, freshwater planarians have also become partners of symbiotic ciliates from the class Oligohymenophorea. In the present study, we explored the hidden diversity and addressed the questionable systematic position of mouthless obligatory gut endosymbionts of freshwater planarians, using the nuclear and mitochondrial SSU...

Potamophilus kelabitensis sp. nov., a new riffle beetle (Coleoptera, Elmidae) discovered in the Kelabit Highlands (northern Sarawak) and Sapulut environment (southern Sabah), is described. Illustrations of the habitus and diagnostic characters of the new species are presented. Differences from the type species P. acuminatus (Fabricius, 1792) from t...

Tetrahymena comprises over 80 free‐living as well as facultative or obligate histophagous species parasitizing especially invertebrates and fishes. Because of the comparatively high morphological conservativeness of tetrahymenids, their identification is primarily based on the gene coding for cytochrome c oxidase subunit I (COI). In addition to thi...

Many hypotrich genera, including Trachelostyla, are taxonomically challenging and in a need of integrative revision. Using morphological data, molecular phylogenetic analyses, and internal transcribed spacer 2 (ITS2) secondary structures, we attempt to cast more light on species relationships within the genus Trachelostyla. The present multifaceted...

Phylogenetically distinct lineages may be hidden behind identical or highly similar morphologies. The phenomenon of morphological crypticity has been recently detected in symbiotic ciliates of the family Clevelandellidae, as multivariate and Fourier shape analyses failed to distinguish genetically distinct taxa. To address the question of species b...

The cell mouth is a property of the vast majority of free-living and endosymbiotic/epibiotic ciliates of the class Oligohymenophorea. Cytostome, however, naturally absents in the whole endosymbiotic subclass Astomatia and was naturally or experimentally lost in a few members of the subclass Hymenostomatia. This poses a question of how homoplastic m...

Study question The aim of the study was to identify molecules in the embryo culture medium as important predictive biomarkers of high-quality embryos Summary answer The study identified 14 canonical iso-miRNA molecules that prognostically determine the quality of the embryo with a prediction accuracy with 95% sensitivity and 80% specificity. What...

The species of Elmomorphus Sharp, 1888 occurring in Japan and Korea are redescribed and illustrated: E. brevicornis Sharp, 1888 (Japan, Korea) and E. amamiensis Nomura, 1959 (Japan). The standard barcoding fragment of the mitochondrial gene coding for cytochrome c oxidase subunit I (COI) was sequenced and used together with morphological characters...

The presence of parasitic ciliates of the hymenostome genus Tetrahymena was examined in 150 mollusks belonging to six bivalve and 13 gastropod species in Slovakia, Central Europe. Tetrahymenids were detected only in two species, viz., in the invasive Lusitanian slug (Arion vulgaris) and in the native swollen river mussel (Unio tumidus). Although on...

Coevolution of endosymbionts with their hosts plays an important role in the processes of speciation and is among the most fascinating topics in evolutionary biology. Astome ciliates represent an interesting model for coevolutionary studies because they are so tightly associated with their host organisms that they completely lost the cell oral appa...

Mobilids are among the most taxonomically diverse but morphologically uniform groups of epibiotic ciliates. They attach to their hosts by means of an adhesive disc as harmless commensals such as Urceolaria, or as parasites causing significant economic loss such as some Trichodina species. We investigated the diversity, species boundaries, and phylo...

Lepidochaetus is a phylogenetically interesting genus, as it represents one of the deepest branching lineages within the highly diverse family Chaetonotidae. Its taxonomy is, however, very complex due to multiple insufficient morphological descriptions, proposed synonymizations, and availability of molecular data for only two species. In the presen...

The morphology and ontogenesis of two new hypotrich ciliates, Hemiholosticha solitaria and Hemiholosticha germanica, were studied using live observation, protargol impregnation, and scanning electron microscopy. Both species share a medium-sized, almost globular body with a short anterior projection; two macronuclear nodules with a single micronucl...

The Colpodea form a major clade of ciliates that are often found in environmental DNA sequencing studies. They are united by similar somatic ciliature, but differentiated by complex oral structures. Although there are four well supported colpodean subclades, there is disagreement in molecular phylogenetic inferences about their branching order. Usi...

Astome ciliates are a diverse group of obligate endosymbionts, living in the alimentary tract of invertebrates and vertebrates. In the digestive tube of two endogeic lumbricid earthworms, we discovered Metaradiophrya speculorum sp. n. and re-discovered Maupasella mucronata after almost half a century. Their systematic positions were determined usin...

Morphogenesis of ciliated protists attracts a lot of attention, because their huge morphological diversity is related to formation of ciliary structures during cell division. In the present work, the morphology and morphogenesis as well as the phylogenetic position of a new, marine hypotrich ciliate, Nothoholosticha luporinii n. sp., were investiga...

Background: Various ecological groups of earthworms very likely constitute sharply isolated niches that might permit speciation of their symbiotic ciliates, even though no distinct morphological features appear to be recognizable among ciliates originating from different host groups. The nuclear highly variable ITS1-5.8S-ITS2 region and the hyperv...

The endozoic ciliates of the family Clevelandellidae Kidder, 1938 typically inhabit the hindgut of wood-feeding panesthiine cockroaches. To assess the consistency of species delimitation in clevelandellids, we tested the utility of three sources of taxonomic data: morphometric measurements, cell geometrical information, and 18S rRNA gene sequences....

Myxophyllum steenstrupi is a symbiotic ciliate living in the body slime and mantle cavity of terrestrial pulmonates (Gastropoda: Pulmonata). In the present study, M. steenstrupi was rediscovered after almost 30 years and characterized using an integrative morpho-molecular approach for the first time. Myxophyllum is distinguished by a broadly ovate,...

Planarians represent an insufficiently explored group of aquatic invertebrates that might serve as hosts of histophagous ciliates belonging to the hymenostome genus Tetrahymena. During our extensive research on freshwater planarians, parasitic tetrahymenas were detected in two of the eight planarian species investigated, namely, in Dugesia gonoceph...

Two new ciliate species, Clevelandella lynni sp. n. and Nyctotherus galerus sp. n., were discovered in the hindgut of wood-feeding panesthiine cockroaches. Their morphology was studied using standard methods and their phylogenetic positions within the order Clevelandellida were determined using the 18S rRNA gene sequences. Clevelandella lynni is ch...

Genetic patterns of lichenized fungi often display a mosaic-like and difficult to interpret structure blurring their evolutionary history. The genetic diversity and phylogeographic pattern of a mycobiont of the predominantly Mediterranean dwelling lichen Solenopsora candicans were investigated on the base of extensive sampling (361 individuals, 77 po...

Genetic patterns of lichenized fungi often display a mosaic-like and difficult to interpret structure blurring their evolutionary history. The genetic diversity and phylogeographic pattern of a mycobiont of the predominantly Mediterranean dwelling lichen Solenopsora candicans were investigated on the base of extensive sampling (361 individuals, 77...

The ciliate genus Spirostomum comprises eight morphospecies, inhabiting diverse aquatic environments worldwide, where they can be used as water quality indicators. Although Spirostomum species are relatively easily identified using morphological methods, the previous nuclear rDNA-based phylogenies indicated several conflicts in morphospecies deline...

Four earthworm species, the endogeic Octolasion tyrtaeum (Savigny, 1826), the anecic Lumbricus terrestris Linnaeus, 1758 as well as the epigeic Eisenia fetida (Savigny, 1826) and Dendrobaena veneta (Rosa, 1886), were examined for the presence of astome ciliates. Based on the integrative taxonomic approach, five ciliate species were recognized in th...

Four common earthworm species, the anecic Lumbricus terrestris, the endogeic Octolasion tyrteum as well as the epigeic Eisenia fetida and Dendrobaena veneta, were examined for the presence of the microbial gut symbiont Plagiotoma lumbrici. The evolutionary origin of this endobiotic microbe was reconstructed, using the 18S rRNA gene, the ITS1‐5.8S‐I...

Date palm (Phoenix dactylifera) can accumulate as much as 1% silicon (Si), but not much is known about the mechanisms inherent to this process. Here, we investigated in detail the uptake, accumulation and distribution of Si in date palms, and the phylogeny of Si transporter genes in plants. We characterized the PdNIP2 transporter following heterolo...

The morphology and phylogenetic position of a haptorian ciliate, Phialina pupula (Müller, 1773) Foissner, 1983, isolated from microaerobic sandy sediments of the floodplain area of the Boise River, Idaho, U.S.A., were studied using live observation, protargol impregnation, scanning electron microscopy, and the 18S rRNA gene as well as the ITS regio...

Three freshwater turbellarian species (Dugesia gonocephala, Girardia tigrina, and Polycelis felina), belonging to the order Tricladida, were examined for the presence of ciliates. Living morphology and phylogenetic position of the isolated ciliates were studied using light microscopy and molecular phylogenetic methods. Three ciliate species, all fr...

The morphology, ontogenesis, conjugation, and phylogenetic position of Metopus boletus nov. spec. were studied using live observation, various silver impregnation methods, scanning electron microscopy, morphometry, and the 18S rRNA gene sequence. The new species is outstanding in having a mushroom-like appearance; a globular to broadly ellipsoid ma...

Abstract The hindgut of wood-feeding Panesthia cockroaches harbours a diverse microbial community, whose most morphologically prominent members are bacterivorous clevelandellid ciliates. Co-occurrence and correlation patterns of prokaryotes associated with these endosymbiotic ciliates were investigated. Multidimensional scaling based on taxa intera...

We critically re-analyzed the 18S rRNA gene phylogeny of the ciliate class Colpodea where four main lineages have been recognized: (1) Bursariomorphida including bryometopids, (2) Platyophryida including sorogenids, (3) Cyrtolophosidida, and (4) Colpodida including bryophryids and grossglockneriids. The Platyophryida branched off first and the Cyrt...

Batesian mimicry is a relationship in which a harmful organism (the model) is mimicked by a harmless organism (the mimic), which gains protection because predators mistake it for the model. It is the most widely studied of mimicry complexes and has undoubtedly played an important role in the speciation of various animals especially insects. However...

Members of the class Armophorea occur in microaerophilic and anaerobic habitats, including the digestive tract of invertebrates and vertebrates. Phylogenetic kinships of metopid and clevelandellid armophoreans conflict with traditional morphology‐based classifications. To reconcile their relationships and understand their morphological evolution an...

Based on intrinsic morphological and extrinsic bionomic characters, the systematic position of the weevil tribe Acentrusini Alonso-Zarazaga, 2005 (Coleoptera: Curculionidae: Curculioninae) was determined. Maximum parsimony and Bayesian inference as well as nonmetric multi-dimensional scaling were used to analyze 34 morphological characters of adult...

The class Litostomatea represents a highly diverse but monophyletic group, uniting both free-living and endosymbiotic ciliates. Ribosomal RNA genes and ITS-region sequences helped to recognize and define the main litostomatean lineages, but did not provide enough phylogenetic signal to unambiguously resolve their interrelationships. In this study,...

Trichostome ciliates are among the most conspicuous protists in the gastrointestinal tract of a large variety of vertebrates. However, little is still known about phylogeny of the trichostome/vertebrate symbiotic systems, evolutionary correlations between trichostome extrinsic traits, and character-dependent diversification of trichostomes. These i...

Morphology, systematic position and time-calibrated phylogeny of Haptophrya planariarum were investigated. This endosymbiont of freshwater turbellarians is characterized by: (i) a length of about 200-900 μm; (ii) a campanulate to truncate claviform body carrying an anterior adhesive sucker; (iii) an ellipsoidal macronucleus localized in the rear bo...

Ciliates are a suitable microbial model to investigate trait-dependent diversification because of their comparatively complex morphology and high diversity. We examined the impact of seven intrinsic traits on speciation, extinction, and net-diversification of rhynchostomatians, a group of comparatively large, predatory ciliates with proboscis carry...

Understanding transcontinental biogeographic patterns has been one of the main foci of the field of biogeography. While multiple explanations for transcontinental disjunctions have been proposed, little is still known about the relative importance of intrinsic and extrinsic traits for the diversification dynamics of disjunct taxa. Here, we study th...

Ciliates are unicellular eukaryotic microorganisms that express their behaviour by motion. In this study, the authors attempt to address the question of whether locomotion could reflect evolutionary history or whether it instead depends on cell geometry and/or lifestyle. To this end, the authors investigated locomotory behaviour of two predatory ci...

We isolated seven spathidiids from various terrestrial habitats in Korea: Enchelys megaspinata sp. nov.; Spathidium ascendens Wenzel, 1955; S. papilliferum Kahl, 1930; S. polynucleatum (Foissner et al., 2002) comb. nov.; S. rectitoratum Kahl, 1930; S. securiforme Kahl, 1930 stat. nov.; and Apobryophyllum schmidingeri Foissner and Al-Rasheid, 2007....

Phylogenetic position of some free-living litostomatean taxa has not been correctly determined because of long-branch artifacts in 18S rRNA gene trees. The main aim of this study was to test the effectiveness of various masking algorithms, tree-building techniques, binarization of DNA data as well as combining morphological and molecular data to el...

The very diverse and comparatively complex morphology of ciliates has given rise to numerous taxonomic concepts. However, the information content of the utilized molecular markers has seldom been explored prior to phylogenetic analyses and taxonomic decisions. Likewise, robust testing of morphological homology statements and the apomorphic nature o...

The morphology and morphogenesis of a new Australian metopid ciliate, Lepidometopus platycephalus nov. gen., nov. spec., were studied using live observation, various silver impregnation methods, scanning electron microscopy, and morphometry. The new genus is outstanding in having epicortical scales (lepidosomes) and a strongly flattened and distinc...

We investigated interrelationships between four free-living litostomatean lineages, using 18S rRNA gene and ITS region sequences as well as the secondary structure of the ITS2 molecules. Our phylogenetic analyses confirmed the deep split of free-living litostomateans into Rhynchostomatia and Haptoria represented here by Haptorida, Pleurostomatida,...

Six metopid ciliates from soil of the Murray River floodplain in Australia were studied using live observation, various silver impregnation methods, scanning electron microscopy, and multivariate statistics. One of the species is affiliated with M. setosus while the others represent new taxa. Metopus filum nov. spec. is distinguished from most cong...

Five strains (CCY 058-007-001T, CCY 058-007-002, CCY 058-007-003, CCY 058-007-004 and CCY 058-007-005) of a novel parasitic yeast belonging to the genus Taphrina were isolated from leaf tissues of Geum montanum L. (Rosaceae), collected from the Vysoké Tatry Mts., Slovakia. Genetic analyses revealed that these isolates differ by 15 unique substituti...

The response of ciliate communities to cyanobacterial bloom was investigated in a shallow, hypertrophic reservoir in Slovakia, Central Europe. Seasonal dynamics of ciliate communities corresponded negatively with course of water bloom formation. The highest numbers and abundances of ciliate species occurred during the spring season when cyanobacter...

Resting cysts of Parentocirrus hortualis were investigated, using live observation, SEM and TEM. Processes during encystation and excystation were observed in vivo under the light microscope. During encystation, the trophic body becomes globular, the ciliature is resorbed in an anterior direction, the macronuclear nodules fuse into an elongated mas...

Reconstruction of evolutionary history of the ciliate order Spathidiida has proven elusive. There are weakly statistically supported deeper nodes in 18S rRNA gene phylogenies on one hand, while several statistically strongly supported clusters containing morphologically dissimilar taxa that usually lack any common apomorphies on the other hand. To...

Since ciliates rarely possess structures that easily fossilize, we are limited in our ability to use paleontological studies to reconstruct the early evolution of this large and ecologically important clade of protists. Tintinnids, a group of loricate (house-forming) planktonic ciliates, are the only group that has a significant fossil record. Puta...

The class Litostomatea comprises a diverse assemblage of free-living and endosymbiotic ciliates. To understand diversification dynamic of litostomateans, divergence times of their main groups were estimated with the Bayesian molecular dating, a technique allowing relaxation of molecular clock and incorporation of flexible calibration points. The cl...

The order Dileptida is a small group of predatory ciliates characterized by a proboscis serving for prey capture. Although monophyly of the order is strongly supported, generic relationships between dileptid taxa were left mostly unresolved in 18S rRNA gene phylogenies. To overcome this problem, we applied the synergistic effect of combining multip...

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A checklist of ciliates from the family Euplotidae recorded in the territory of Slovakia, Central Europe was assembled. Altogether, 11 species belonging to three genera of the family Euplotidae have been reported there: Euplotes alatus, Euplotes charon, Euplotes moebiusi, Euplotoides aediculatus, Euplotoides eurystomus, Euplotoides patella, Euploto...

We isolated a relatively unknown haptorian ciliate, Trachelophyllum brachypharynx, in brackish water from the mouth of the Taehwa River, South Korea. The morphology of this isolate was studied using in vivo observation and protargol impregnation, and its evolutionary history was revealed by phylogenetic analysis of the 18S rRNA gene. The main featu...