Phylogenetic relationships of the Nassulida within the phylum Ciliophora inferred from the complete small subunit rRNA gene sequences of Furgasonia blochmanni, Obertrumia georgiana, and Pseudomicrothorax dubius

CMF22 is a broadly conserved axonemal protein and is required for propulsive motility in Trypanosoma brucei

The eukaryotic flagellum (or cilium) is a broadly conserved organelle that provides motility for many pathogenic protozoa and is critical for normal development and physiology in humans. Therefore, defining core components of motile axonemes enhances understanding of eukaryotic biology and provides insight into mechanisms of inherited and infectious diseases in humans. In this study, we show that component of motile flagella 22 (CMF22) is tightly associated with the flagellar axoneme and is likely to have been present in the last eukaryotic common ancestor. The CMF22 amino acid sequence contains predicted IQ and ATPase associated with a variety of cellular activities (AAA) motifs that are conserved among CMF22 orthologues in diverse organisms, hinting at the importance of these domains in CMF22 function. Knockdown by RNA interference (RNAi) and rescue with an RNAi-immune mRNA demonstrated that CMF22 is required for propulsive cell motility in Trypanosoma brucei. Loss of propulsive motility in CMF22-knockdown cells was due to altered flagellar beating patterns, rather than flagellar paralysis, indicating that CMF22 is essential for motility regulation and likely functions as a fundamental regulatory component of motile axonemes. CMF22 association with the axoneme is weakened in mutants that disrupt the nexin-dynein regulatory complex, suggesting potential interaction with this complex. Our results provide insight into the core machinery required for motility of eukaryotic flagella.

"Candidatus Cryptoprodotis polytropus," a novel Rickettsia-like organism in the ciliated protist Pseudomicrothorax dubius (Ciliophora, Nassophorea)

Rickettsia-like organisms (RLO) are obligate, often highly fastidious, intracellular bacterial parasites associated with a variety of vertebrate and invertebrate hosts. Despite their importance as causative agents of severe mortality outbreaks in farmed aquatic species, little is known about their life cycle and their host range. The present work reports the characterization of "Candidatus Cryptoprodotis polytropus," a novel Rickettsia-like bacterium associated with the common ciliate species Pseudomicrothorax dubius by means of the "Full-Cycle rRNA Approach" and ultrastructural observations. The morphological description by in vivo and scanning electron microscopy and the 18S rRNA gene sequence of the host species is provided as well. Phylogenetic analysis based on the 16S rRNA gene supports the inclusion of "Candidatus Cryptoprodotis polytropus" within the family Rickettsiaceae (cl. Alphaproteobacteria) together with the genera Rickettsia and Orientia. Observations on natural ciliate populations account for the occasional nature of this likely parasitic association. The presence of a previously unknown RLO in ciliates sheds a new light on the possible role of protists as transient hosts, vectors or natural reservoir for some economically important pathogens.

Small subunit rRNA phylogenies show that the class nassophorea is not monophyletic (Phylum Ciliophora)

The hypostome ciliates have been generally classified into two classes, Phyllopharyngea and Nassophorea. The status of Nassophorea and its relationship with Phyllopharyngea is one of the most controversial issues in ciliate systematics. Here we focus on the phylogenetic interrelationships of Nassophorea and Phyllopharyngea based on small subunit ribosomal RNA gene sequences. The three nassophorean subgroups, synhymeniids, microthoracids, and nassulids, each emerged as monophyletic, with synhymeniids as a sister group of Phyllopharyngea, and microthoracids as a sister of the synhymeniids+Phyllopharyngea clade in all phylogenies. The exact placement of the nassulids, however, remains uncertain. Following a detailed analysis of phenotypic characters, we hypothesize that: (1) the Phyllopharyngea could have evolved from synhymeniids, with the further development of their subkinetal microtubules as one of the major events; and (2) the development of monokinetid structures, as well as the reduction and specialization of the cyrtos and cortex, might have occurred during the diversifications of the microthoracids, synhymeniids, and Phyllopharyngea from a common ancestor. Expanding the class Phyllopharyngea to include the synhymeniids as a subclass, and designating a new subclass Subkinetalia n. subcl. for the group comprising cyrtophorians, chonotrichians, rhynchodians, and suctorians, are proposed.

Caryotricha minuta (Xu et al., 2008) nov. comb., a unique marine ciliate (Protista, Ciliophora, Spirotrichea), with phylogenetic analysis of the ambiguous genus Caryotricha inferred from the small-subunit rRNA gene sequence

A population of Kiitricha minuta Xu et al., 2008, a small kiitrichid ciliate, was isolated from a brackish water sample in Jiaozhou Bay, Qingdao, northern China. After comparison of its morphology and infraciliature, it is believed that this morphotype should be assigned to the genus Caryotricha; hence, a new combination is suggested, Caryotricha minuta (Xu et al., 2008) nov. comb. The small-subunit (SSU) rRNA gene sequence was determined in order to elucidate the phylogenetic position of this poorly known, ambiguous genus. The organism can be clearly separated from its congener, Caryotricha convexa Kahl, 1932, by the extremely shortened ventral cirral rows in the posterior ends. Based on the data available, an improved diagnosis is given for the genus: marine Kiitrichidae with prominent buccal field; two highly developed undulating membranes; non-grouped, uniform cirral rows on both ventral and dorsal sides; enlarged transverse cirri present, which are the only differentiated cirri; marginal cirri not present; one short migratory row located posterior to buccal field; structure of dorsal kineties generally in Kiitricha pattern. The sequence of the SSU rRNA gene of C. minuta differs by 13 % from that of Kiitricha marina. Molecular phylogenetic analyses (Bayesian inference, least squares, neighbour joining, maximum parsimony) indicate that Caryotricha, together with Kiitricha, diverges at a deep level from all other spirotrichs. Its branching position is between Phacodiniidia and Licnophoridia. The results strongly support the distinct separation of the Kiitricha-Caryotricha clade, which always branches basal to the Stichotrichia-Hypotrichia-Oligotrichia-Choreotrichia assemblage. These results also confirm the previous hypothesis that the Kiitricha-Caryotricha group, long assumed to be a close relation to the euplotids, represents a taxon at subclass level within the spirotrichs.

Balanion masanensis n. sp. (ciliophora: prostomatea) from the coastal waters of Korea: morphology and small subunit ribosomal RNA gene sequence

The planktonic ciliate Balanion masanensis n. sp. is described from living cells, from cells prepared by quantitative protargol staining (QPS), scanning electron microscopy (SEM), and transmitted electron microscopy (TEM) preparations, and the sequence of its nuclear small subunit rDNA (SSU rDNA) is reported. This species is almost ovoid with a flattened anterior oral region when the cells are alive and stained. The flattened anterior region of a living cell often forms a dome with the perimeter receded in a groove, and this region is easily inflated or depressed. In SEM photos, a brosse of six to nine monokinetids (or possibly three to five dikinetids) was observed inside the circumoral dikinetids. In TEM photos, circumoral microtubular ribbons were observed below the oral cilia, which along with the oral flaps were 8-16 microm in length. The cytostome is a slight funnel-like central depression on the flattened anterior end. The morphological characteristics of this ciliate are identical to those of the genus Balanion (Order Prorodontida). The ranges (and mean+/-standard deviation) of cell length, cell width, and oral diameter of living cells (n=23-26) were 27-43 microm (35.2+/-4.6), 25-32 microm (28.6+/-2.3), and 25-30 microm (27.6+/-1.3), respectively, while those of the QPS-stained specimens (n=70) were 23-37 microm (30.6+/-3.5), 26-35 microm (30.7+/-2.2), and 26-33 microm (29.5+/-1.5), respectively. Forty-six to 55 somatic kineties (SKs) were equally spaced around the cell body and extended from the oral to near the posterior regions with 24-50 monokinetids per kinety. Each kinetid bore a cilium 2.8-7.2 microm long. A caudal cilium (ca 14 microm long) arose on the posterior end. The single ellipsoid macronucleus is 6.8-13.4 x 6.8-10.5 microm, accompanied by a single micronucleus (2.0-2.8 x 1.5-2.5 microm) visible only in QPS specimens. Because, the cell size, the number of SKs, and the number of kinetosomes per SK of this ciliate were much greater than those of Balanion comatum and Balanion planctonicum, the only two Balanion species so far reported, we have established B. masanensis n. sp. When properly aligned, the sequence of the SSU rDNA of B. masanensis n. sp. (GenBank Accession No. AM412525) was approximately 9% different from that of Coleps hirtus (Colepidae, Prorodontida) and 12% different from that of Prorodon teres (Prorodontidae, Prorodontida).

Molecular systematics and ultrastructural characterization of a forgotten species: Chattonidium setense (Ciliophora, Heterotrichea)

In the present paper we redescribe the ciliate Chattonidium setense Villeneuve 1937 combining morphological observations (live, stained, scanning, and transmission electron microscope) with behavioral notes and molecular data. Ultrastructural analysis revealed remarkable similarities between Chattonidium and representative members of the class Heterotrichea in cortical structure and cytoplasmic organization. The most similar genus for these aspects appears to be Condylostoma. To verify this relatedness, 18S rRNA genes from Chattonidium and from one Condylostoma species were sequenced. Phylogenetic analysis indicates Chattonidium belongs to the class Heterotrichea defined according to the modern taxonomy, and confirms its relatedness with Condylostoma already hypothesized by Villeneuve-Brachon (1940). The presence of the aboral cavity complex, a unique feature never described in other ciliates, and its peculiar organization revealed by ultrastructural analysis fully justify, in our opinion, the maintenance of Chattonidium in the separate family Chattonidiidae, established by Villeneuve-Brachon in 1940.

Reevaluation of the phylogenetic relationship between mobilid and sessilid peritrichs (Ciliophora, Oligohymenophorea) based on small subunit rRNA genes sequences

Based on morphological characters, peritrich ciliates (Class Olygohymenophorea, Subclass Peritrichia) have been subdivided into the Orders Sessilida and Mobilida. Molecular phylogenetic studies on peritrichs have been restricted to members of the Order Sessilida. In order to shed more light into the evolutionary relationships within peritrichs, the complete small subunit rRNA (SSU rRNA) sequences of four mobilid species, Trichodina nobilis, Trichodina heterodentata, Trichodina reticulata, and Trichodinella myakkae were used to construct phylogenetic trees using maximum parsimony, neighbor joining, and Bayesian analyses. Whatever phylogenetic method used, the peritrichs did not constitute a monophyletic group: mobilid and sessilid species did not cluster together. Similarity in morphology but difference in molecular data led us to suggest that the oral structures of peritrichs are the result of evolutionary convergence. In addition, Trichodina reticulata, a Trichodina species with granules in the center of the adhesive disc, branched separately from its congeners, Trichodina nobilis and Trichodina heterodentata, trichodinids without such granules. This indicates that granules in the adhesive disc might be a phylogenetic character of high importance within the Family Trichodinidae.

Parastrombidinopsis shimi n. gen., n. sp. (Ciliophora: Choreotrichia) from the coastal waters of Korea: morphology and small subunit ribosomal DNA sequence

The planktonic ciliate Parastrombidinopsis shimi n. gen., n. sp. is described from both living cells and quantitative protargol-stained (QPS) preparations and the sequence of the small subunit rDNA (SSU rDNA) is reported. This species is almost oval when the cells are alive; when stained, it is cylindrical for the upper two-fifths, half-bowl shaped for the middle two-fifths, and narrow rodshaped for the lower one-fifth. The ranges (and mean +/- standard deviation, n = 20) of cell length, cell width, and oral diameter of living cells were 112-221 microm (168 +/- 39), 88-176 microm (121 +/- 30), and 53-110 microm (80 +/- 14), respectively, while those of the QPS-stained specimens (n = 54) were 88-225 microm (162 +/- 29), 55-163 microm (102 +/- 19), and 53-98 microm (69 +/- 9), respectively. Thirty-six to 48 external oral polykinetids had cilia 25-40 microm long. However, unlike Strombidinopsis species sensu stricto, P. shimi has an external oral polykinetid zone that is an open circle. This species has two shorter polykinetids associated with the end of the oral polykinetid zone, deep in the oral cavity. Like Strombidinopsis species in the subclass Choreotrichia, 36-50 somatic kineties were equally spaced around the cell body and extended from the oral to the posterior regions with 68-105 dikinetids per kinety. Both kinetosomes of each kinetid bore cilia 3-10 microm long. Parastrombidinopsis shimi had 2 (1-4) ovoid macronuclei of 20-82 x 15-32 microm. When properly aligned, the sequence of the SSU rDNA of P. shimi (GenBank Accession No. AJ786648) was approximately 5% different from that of Strobilidium caudatum and 6% different from that of two Strombidinopsis species. Based both on morphology and gene sequence divergence, we establish this is as a new species in a new genus belonging to the family Strombidinopsidae.

Phylogenetic position of the marine ciliate, Certesia quadrinucleata (Ciliophora; Hypotrichia; Hypotrichida) inferred from the complete small subunit ribosomal RNA gene sequence

The complete small subunit rRNA (SSrRNA) gene sequence of the rare marine hypotrich, Certesia quadrinucleata Fabre-Domergue, 1885, was determined, and found to be 1752 nucleotides long. The phylogenetic position of this species was deduced using distance matrix, maximum parsimony and maximum likelihood methods. Certesia was consistently demonstrated to be a member of the Aspidisca-Euplotes group and clearly exhibits a very close relationship to the well-known genus Euplotes (99% Bay, 99% LS, 99% NJ, 99% MP). The phylogenetic trees further suggest that: (1) Uronychia and Diophrys, traditionally placed in the family Uronychiidae, branch earlier and share a closer relationship to each other than to other hypotrichs; (2) taxa in Gastrocirrhidae, represented by Euplotidium arenarium, might be an "ancestral" group among "traditional" hypotrichs.

Molecular Phylogeny of Phyllopharyngean Ciliates and their Group I Introns

We analyzed small subunit ribosomal DNA (ssu-rDNA) sequences to evaluate both the monophyly of the ciliate class Phyllopharyngea de Puytorac et al. (1974), and relationships among subclasses. Classifications based on morphology and ultrastructure divide the Phyllopharyngea into four subclasses, the Phyllopharyngia, Chonotrichia, Rhynchodia, and Suctoria. Our analyses of ssu-rDNA genealogies derived from sequence data collected from diverse members representing three of the four subclasses of Phyllopharyngea (Suctoria: Ephelota spp., Prodiscophyra collini, Acineta sp.; Phyllopharyngia: Chlamydodon exocellatus, Chlamydodon triquetrus, Dysteria sp.; and Chonotrichia: Isochona sp.) provide strong support for the monophyly of the Phyllopharyngea, and show that the Chonotrichia emerge from within the Phyllopharyngia. Based on this initial sampling, suctorian budding types are monophyletic, and exogenous budding appears to be basal to evaginative and endogenous budding. Further, we report the discovery of a group I intron at position 891 in the Suctoria Acineta sp. and Tokophrya lemnarum, and a second group I intron at position 1506 in T. lemnarum. These introns represent only the second examples of group I introns in a ciliate ribosomal gene, since the discovery of ribozymes in the LSU rRNA gene of Tetrahymena thermophila. Phylogenetic analyses of Group I introns suggest a complex evolutionary history involving either multiple loses or gains of introns within endogenously budding Suctoria.

Phylogenetic position of Licnophora, Lechriopyla, and Schizocaryum, three unusual ciliates (phylum Ciliophora) endosymbiotic in echinoderms (phylum Echinodermata)

Various echinoderms are colonized by species from several classes of the Phylum Ciliophora, indicating that the echinoderm "habitat" has been invaded independently on numerous occasions throughout evolutionary history. Two "echinoderm" ciliates whose phylogenetic positions have been problematic are Licnophora macfarlandi Stevens, 1901 and Schizocaryum dogieli Poljansky and Golikova, 1957. Licnophora macfarlandi is an endosymbiont of the respiratory trees of holothuroids, and S. dogieli is found in the esophagus of echinoids. A third species, Lechriopyla mystax Lynch, 1930, is a plagiopylid ciliate found in the intestine of echinoids. Host echinoderms were collected near the Friday Harbor Laboratories, San Juan Island, WA. Specimens of S. dogieli and L. mystax were obtained from the esophagus and intestine, respectively, of the sea urchin Strongylocentrotus pallidus. Specimens of L. macfarlandi were collected from the fluid obtained from the respiratory trees of Parastichopus californicus. Using small subunit ribosomal RNA (SSrRNA) sequences of these three ciliates and a global alignment of SSrRNA sequences of other ciliates, we established the following. 1) Licnophora is a spirotrich ciliate, clearly related to the hypotrichs and stichotrichs; this is corroborated by its possession of macronuclear replication bands. 2) Lechriopyla is the sister genus to Plagiopyla and is a member of the Class Plagiopylea, which was predicted based on its cytology. 3) Schizocaryum clusters in the Class Oligohymenophorea and is most closely related to the scuticociliates; there are currently no morphological features known to relate Schizocaryum to the scuticociliates.

Evidence for an independent radiation of endosymbiotic litostome ciliates within Australian marsupial herbivores

The recent discovery of isotrichid-like ciliates occurring as endosymbionts in macropodid marsupials posed interesting questions in regard to both their phyletic origin (all previous records confined to eutherian mammals) and their morphological evolution (Australian forms possibly representing missing links between previously described genera). The SSU rRNA gene was sequenced for three species (Dasytricha dehorityi, D. dogieli, and Bitricha tasmaniensis) and aligned against representatives of all major ciliate classes. The Australian species did not group with the other isotrichid species but instead formed an independent radiation. Discrepancies between recent global phylogenies of the phylum Ciliophora were examined by manipulation of the aligned sequence data set. Sources of conflict between these studies did not stem from differences in outgroup choice or phylogenetic reconstruction methods. Differences in the application of confidence limits and primary sequence alignment have probably resulted in the reporting of spurious associations which are not supported by more conservative confidence or alignment methodology. At present, the ciliate subphylum Intramacronucleata is an unresolved polytomy which may be due to deficiencies in the SSU rRNA gene sequence dataset or indicate that the ciliates radiated into their extant classes by rapid burst-like evolution.

Phylogenetic relationships of the Subclass Peniculia (Oligohymenophorea, Ciliophora) inferred from small subunit rRNA gene sequences

Peniculine ciliates have been recognized as a distinct higher taxon of ciliates for almost 50 years. However, phylogenetic relationships within the Subclass Peniculia are still unsettled. To contribute to our understanding of their phylogeny and provide evidence for the position of Urocentrum turbo, we sequenced its small subunit (SS) rRNA gene and the SSrRNA genes from Lembadion bullinum, Frontonia sp., Paramecium caudatum, Paramecium multimicronucleatum, Paramecium putrinum, and Paramecium woodruffi. Urocentrum turbo was the only one of these species not to exhibit a shortened Helix E10_1, which we conclude characterizes the "higher" peniculines. Except for U. turbo, the peniculines are strongly supported as a monophyletic clade with Lembadion, Frontonia, and Paramecium species forming separate and strongly supported clades by bootstrap analysis using distance matrix, maximum parsimony, and maximum likelihood methods. Urocentrum turbo is associated with different lineages, depending upon the analysis used. The Paramecium species form at least four clades with the Paramecium aurelia subgroup being the most derived. We conclude that the Subclass Peniculia should be divided into two orders, the Order Urocentrida and Order Peniculida, with the latter order having two suborders, the Suborder Frontoniina and Peniculina. We place U. turbo with the peniculines because of shared morphological and stomatogenetic features.

Phylogenetic relationships of the genus Paramecium inferred from small subunit rRNA gene sequences

The genus Paramecium includes species that are well known and very common in freshwater environments. Species of Paramecium are morphologically divided into two distinct groups: the "bursaria" subgroup (foot-shaped) and the "aurelia" subgroup (cigar-shaped). Their placement within the class Oligohymenophorea has been supported by the analysis of the small subunit rRNA gene sequence of P. tetraurelia. To confirm the stability of this placement and to resolve relationships within the genus, small subunit rRNA gene sequences of P. bursaria, P. calkinsi, P. duboscqui, P. jenningsi, P. nephridiatum, P. primaurelia, and P. polycaryum were determined and aligned. Trees constructed using distance-matrix, maximum-likelihood, and maximum-parsimony methods all depicted the genus as a monophyletic group, clustering with the other oligohymenophorean taxa. Within the Paramecium clade, P. bursaria branches basal to the other species, although the remaining species of the morphologically defined "bursaria" subgroup do not group with P. bursaria, nor do they form a monophyletic subgroup. However, the species of the "aurelia" subgroup are closely related and strongly supported as a monophyletic group.

Protein coding gene trees in ciliates: comparison with rRNA-based phylogenies

We have reexamined the phylogeny of the ciliates using alpha-tubulin and phosphoglycerate kinase gene sequences. For alpha-tubulin, we have compared the amino acid and nucleotide sequences of 20 species representing seven of the nine classes of the phylum (Karyorelictea, Heterotrichea, Hypotrichea, Oligohymenophorea, Colpodea, Nassophorea, and Litostomatea). The phylogenetic tree resembles a bush from which three monophyletic lineages can be distinguished which correspond to the three classes Hypotrichea, Oligohymenophorea, and Litostomatea. For phosphoglycerate kinase, we have compared the amino acid sequences from 7 species representing three classes (Heterotrichea, Hypotrichea, and Oligohymenophorea). The branching pattern is resolved in three deeply separated branches with an early emergence of the heterotrich. Our comparative analysis shows that if alpha-tubulin phylogeny is not informative at the interclass level, the preliminary data from the phosphoglycerate kinase molecule appear more promising. Nevertheless, at low taxonomic level and at the class level, the resolved phylogenetic relationships inferred from both protein and rRNA sequence data are congruent.

The small subunit ribosomal RNA gene sequence of Pleistophora anguillarum and the use of PCR primers for diagnostic detection of the parasite

Using the polymerase chain reaction (PCR) and two primers for conserved regions of the small subunit ribosomal RNA (SSU-rRNA) of Microsporidia, a DNA segment about 1,195 base pairs long was amplified from a DNA template prepared from purified spores of the microsporidian species Pleistophora anguillarum. These spores had been isolated from adult eels (Anguilla japonica) with "Beko Disease." A comparison of sequence data from other microsporidian species showed P. anguillarum SSU-rRNA to be most similar to Vavraia oncoperae. When juvenile eels were artificially infected with P. anguillarum, enzyme-linked immunosorbent assay could detect a positive infection only 12 days post-infection. However, when suitable PCR primers were used, a DNA fragment of about 0.8 kb was detected from these juvenile eels after only 3 days post infection. No PCR product was obtained with templates prepared from clinically healthy control animals.

Phylogenetic analysis of the rumen ciliate family Ophryoscolecidae based on 18S ribosomal RNA sequences, with new sequences fromDiplodinium,Eudiplodinium, andOphryoscolex

Phylogenetic relationships within the largest family of entodiniomorphid rumen ciliates, the Ophryoscolecidae, were inferred from comparisons of small-subunit ribosomal RNA gene sequences. These included three new sequences from Diplodinium dentatum (1638 base pairs (bp)), Eudiplodinium maggii (1637 bp), and Ophryoscolex purkynjei (1636 bp). Using morphological characters, Lubinsky constructed a cladogram of the Ophryoscolecidae, and on the basis of his analysis, he divided the family into three subfamilies (Entodiniinae, Diplodiniinae, Ophryoscolecinae) to reflect his "natural" groupings (G. Lubinsky. 1957. Can. J. Zool. 35: 141 – 159). Our cladistic analysis, based on the limited morphological and ultrastructural data available, indicates that there are no synapomorphies supporting the Diplodiniinae sensu Lubinsky. However, based upon the six 18S sequences for the Ophryoscolecidae, the rumen ciliates are monophyletic and fall into three distinct groups corresponding to Lubinsky's subfamilial division of the family. Our molecular analysis shows Entodinium to be the earliest branching rumen ciliate (subfamily Entodiniinae) and Eudiplodinium, not Diplodiium, branching first among the diplodiniines.

Phylogeny of the rumen ciliates Entodinium, Epidinium and Polyplastron (Litostomatea:Entodiniomorphida) inferred from small subunit ribosomal RNA sequences

There complete 18S ribosomal RNA gene sequences from the rumen ciliates, Entodinium caudatum (1,639 bp), Epidinium caudatum (1,638 bp), and Polyplastron multivesiculatum (1,640 bp) were determined and confirmed in the opposite direction. Trees produced using maximum parsimony and distance-matrix methods (least squares and neighbour-joining), with strong bootstrap support, depict the rumen ciliates as a monophyletic group. Entodinium caudatum is the earliest branching rumen ciliate. However, Entodinium simplex does not pair with En. caudatum, but rather with Polyplastron multivesiculatum. Signature sequences for these rumen ciliates reveal that the published SSrRNA gene sequence from En. simplex is in fact a Polyplastron species. The free-living haptorian ciliates, The Loxophyllum, Homalozoon and Spathidium (Subclass Haptoria), are monophyletic and are the sister group to the rumen ciliates. The litostomes (Class Litostomatea), consisting of the haptorians and the rumen ciliates, are also a monophyletic group.