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Metopid armophoreans are ciliates commonly found in anaerobic environments worldwide; however, very little is known of their fine structure. In this study, the metopid Parametopidium circumlabens (Biggar and Wenrich 1932) Aescht, 1980, a common endocommensal of sea urchins, is investigated for the first time with emphasis on transmission electron microscopy, revealing several previously unknown elements of its morphology. Somatic dikinetids of P. circumlabens have a typical ribbon of transverse microtubules, an isolated microtubule near triplets 4 and 5 of the anterior kinetosome, plus two other microtubules between anterior and posterior kinetosomes, a short kinetodesmal striated fiber and long postciliary microtubules. In the dikinetids of the perizonal stripe, the kinetodesmal fiber is very pronounced, and there is a conspicuous microfibrillar network system associated with the kinetosomes. A new structure, shaped as a dense, roughly cylindrical mass surrounded by microtubules, is found associated with the posterior kinetosome of perizonal dikinetids. The paroral membrane is diplostichomonad and the adoral membranelles are of the "paramembranelle" type. Bayesian inference and maximum-likelihood analysis of the 18S-rDNA gene unambiguously placed P. circumlabens as sister group of the cluster formed by ((Atopospira galeata, Atopospira violacea) Metopus laminarius) + Clevelandellida, corroborating its classification within the Metopida., (© 2015 The Author(s) Journal of Eukaryotic Microbiology © 2015 International Society of Protistologists.)

Ciliates occur in all major aquatic and soil environments worldwide and are important links in the microbial food webs, which, along with other free-living protists, are generally overlooked in biodiversity conservation programs. In Brazil, the northern region comprises the Brazilian Amazonia, an area widely known for its huge biodiversity. However, the diversity of ciliates in that region is still almost unknown. As result of the present study, a total of 21 species of ciliates, distributed among 15 genera, were inventoried from samples of eutrophized water collected in the city of Belém, capital of the state of Pará, one of the states which comprise the Brazilian Amazonia. In addition, a local population of the rare scuticociliate Cristigera hammeri is described from optical and electron microscopy observations, and its synonymy with C. pleuronemoides is rejected based on new evidence., (Copyright © 2014 Elsevier GmbH. All rights reserved.)

Pseudokeronopsidae Borror & Wicklow, 1983 are biotechnologically important ciliate protists which produce toxic defense substances; however, their diversity is still little known in Brazil. In the present study, Tetrakeronopsis silvanetoi, a new genus and species of marine pseudokeronopsid hypotrichs is described from samples of water with bottom sediment collected from the coast of São Paulo state. Its phylogenetic affinities to the "core urostyloids" are hypothesized based on analyses of the 18S-rDNA marker, and a new subfamily, the Nothoholostichinae subfam. nov., is erected to name the monophylum composed of pseudokeronopsids in which the anterior corona is usually formed by four frontal cirri. In addition, the new combination Monocoronella longissima comb. nov. is proposed for Nothoholosticha longissima (Dragesco & Dragesco-Kernéis, 1986) Li et al., 2009.

Morphology of the urostylid ciliate Hemicycliostyla sphagni Stokes, 1886, the type of Hemicycliostyla Stokes, 1886, is investigated based on live and protargol-impregnated specimens from a Brazilian population. The absence of transverse cirri, which has been considered the main diagnostic feature of Hemicycliostyla, separating it from Pseudourostyla Borror, 1972, was found to vary within the studied population, with 50% of the specimens exhibiting inconspicuous and/or rudimentary transverse cirri. A redefinition of Hemicycliostyla was possible based on combined features of interphase and divisional morphogenesis: Retroextendia Berger, 2006, with bi- or multicoronal frontal cirral pattern; fronto-terminal cirri present; multiple left and right marginal cirral rows that replicate independently via within-row development, each parental row producing one primordium per divider; caudal cirri lacking; and presence/absence of transverse cirri may be intrapopulationally variable. Phylogenetic analyses of the 18S rDNA marker unambiguously placed H. sphagni as sister group of Pseudourostyla franzi Foissner, 1987, which is herein transferred to Hemicycliostyla as Hemicycliostyla franzi comb. nov.

The ciliate Parasterkiella thompsoni (Foissner, 1996) nov. gen., nov. comb. was originally described from Antarctica. In the present study, we report the morphology, morphogenesis during cell division, and molecular phylogeny inferred from the 18S-rDNA sequence of a population isolated from the Rancho Hambre peat bog, Tierra del Fuego Province (Argentina). The study is based on live and protargol-impregnated specimens. Molecular phylogeny was inferred from trees constructed by means of the maximum parsimony, neighbor joining, and Bayesian analyses. The interphase morphology matches the original description of the species. During the cell division, stomatogenesis begins with the de novo proliferation of two fields of basal bodies, each one left of the postoral ventral cirri and of transverse cirri, which later unify. Primordia IV-VI of the proter develop from disaggregation of cirrus IV/3, while primordium IV of the opisthe develops from cirrus IV/2 and primordia V and VI from cirrus V/4. Dorsal morphogenesis occurs in the Urosomoida pattern-that is, the fragmentation of kinety 3 is lacking. Three macronuclear nodules are generated before cytokinesis. Phylogenetic analyses consistently placed P. thompsoni within the stylonychines. New data on the morphogenesis of the dorsal ciliature justifies the transference of Sterkiella thompsoni to a new genus Parasterkiella., (Copyright © 2011 Elsevier GmbH. All rights reserved.)

Since molecular phylogenies of stichotrich ciliates started to be published, some remarkable contradictions to morphology-based classifications have been reported, such as the Convergent Evolution of Urostylids and Uroleptids (CEUU) hypothesis, the Halteria paradox, the polyphyly of Oxytricha and of Stichotrichia. We hypothesized the internal phylogeny of 18S-rDNA from 53 morphological species of stichotrichs and their relationships with Hypotrichia and Oligotrichia using parsimony and neighbor-joining methods, including new data from Pseudouroleptus caudatus and Strongylidium pseudocrassum. Competing phylogenetic scenarios were compared using statistical tests, and the results suggest the reconsideration of both CEUU and the position of Halteria among flexible-body oxytrichids. The polyphyly of Oxytricha was not rejected and the monophyly of Stichotrichia was accepted based on parsimony analysis if Pseudoamphisiella is considered an external (discocephalid related) taxon.