Redescription of Atopospira galeata (Kahl, 1927) nov. comb. and A. violacea (Kahl, 1926) nov. comb. with redefinition of Atopospira Jankowski, 1964 nov. stat. and Brachonella Jankowski, 1964 (Ciliophora, Armophorida)

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 and diversification, we utilized the molecular clock theory as well as information contained in the estimated time trees and morphology of extant taxa. The radiation of the last common ancestor of metopids and clevelandellids very likely occurred during the Paleozoic and crown diversification of the endosymbiotic clevelandellids dates back to the Mesozoic. According to diversification analyses, endosymbiotic clevelandellids have higher net diversification rates than predominantly free-living metopids. Their cladogenic success was very likely associated with sharply isolated ecological niches constituted by their hosts. Conflicts between traditional classifications and molecular phylogenies of metopids and clevelandellids very likely come from processes, leading to further diversification without extinction of ancestral lineages as well as from morphological plesiomorphies incorrectly classified as apomorphies. Our study thus suggests that diversification processes and reconstruction of ancestral morphologies improve the understanding of paraphyly which occurs in groups of organisms with an apparently long evolutionary history and when speciation prevails over extinction.

“…Identification followed Kahl (), Foissner and Agatha (), Foissner et al. (), Bourland and Wendell (), and Vďačný and Foissner ().…”

Section: Methodsmentioning

confidence: 81%

Section: Discussionmentioning

confidence: 99%

A Proposed Timescale for the Evolution of Armophorean Ciliates: Clevelandellids Diversify More Rapidly Than Metopids

Vďačný

Rajter

Stoeck

et al. 2018

“…(). However, these two species can be easily distinguished by their body sizes (65–90 × 30–50 μm vs. 30–55 × 18–35 μm), the numbers of somatic kineties (18–21 vs. 12–15) and adoral polykinetids (21–29 vs. 13–19), the distributional pattern of cortical granules (scattered vs. dense), and the accumulation of cytoplasmic granules in the preoral dome (present vs. absent); the latter is an important feature for delimiting Metopus species (Bourland and Wendell ; Bourland et al. ; Foissner et al.…”

Section: Discussionmentioning

confidence: 99%

“…MEMBERS of the ciliate genus Metopus Claparède and Lachmann, 1858 are widely distributed in anaerobic and microaerobic freshwater, terrestrial, and marine habitats (Bourland and Wendell ; Bourland et al. , ; Corliss ; Da Silva‐Neto et al.…”

mentioning

confidence: 99%

Morphology and Phylogeny of the Soil Ciliate Metopus yantaiensis n. sp. (Ciliophora, Metopida), with Identification of the Intracellular Bacteria

Omar

Zhang

Zou

et al. 2017

The morphology and infraciliature of a new ciliate, Metopus yantaiensis n. sp., discovered in coastal soil of northern China, were investigated. It is distinguished from its congeners by a combination of the following features: nuclear apparatus situated in the preoral dome; 18-21 somatic ciliary rows, of which three extend onto the preoral dome (dome kineties); three to five distinctly elongated caudal cilia, and 21-29 adoral polykinetids. The 18S rRNA genes of this new species and two congeners, Metopus contortus and Metopus hasei, were sequenced and phylogenetically analyzed. The new species is more closely related to M. hasei and the clevelandellids than to other congeners; both the genus Metopus and the order Metopida are not monophyletic. In addition, the digestion-resistant bacteria in the cytoplasm of M. yantaiensis were identified, using a 16S rRNA gene clone library, sequencing, and fluorescence in situ hybridization. The detected intracellular bacteria are affiliated with Sphingomonadales, Rhizobiales, Rickettsiales (Alphaproteobacteria), Pseudomonas (Gammaproteobacteria), Rhodocyclales (Betaproteobacteria), Clostridiales (Firmicutes), and Flavobacteriales (Bacteroidetes).

“…). Details on fine structure of armophoreans, which might provide important data for tracing homologies, are only known for a few species (for a review, see Lynn ), and in addition, molecular data available to propose phylogenetic hypotheses is also relatively scarce when compared to other ciliate classes (Bourland and Wendell ; da Silva Paiva et al. ).…”

mentioning

confidence: 99%

Fine Structure and Molecular Phylogeny of Parametopidium circumlabens (Ciliophora: Armophorea), Endocommensal of Sea Urchins

Silva‐Neto

Paiva

Borges

et al. 2015

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.