Biodiversity and molecular phylogeny of Australian Clevelandella species (Class Armophorea, Order Clevelandellida, Family Clevelandellidae), intestinal endosymbiotic ciliates in the wood-feeding roach Panesthia cribrata Saussure, 1864

Reductitherus cryptostomus n. gen., n. sp. (Ciliophora: Armophorea: Clevelandellida), a remarkable new nyctotherid from an Australian cockroach, Parapanesthia gigantea (Blaberidae: Panesthiinae)

Ciliates of the family Nyctotheridae (Armophorea: Clevelandellida) are frequent intestinal symbionts of various invertebrates and some poikilotherm vertebrates. Depending on the classification scheme, there are between 15 and 18 recognized genera of Nyctotheridae, the majority of which exhibit a rather uniform morphology. They have round to ellipsoidal cells with an adoral zone of membranelles that begins anteriorly in an adoral groove and continues posteriorly into the buccal cavity where it extends deep into the cell in the peristomial funnel. The taxonomy of the Nyctotheridae is primarily based on the number and location of kinetal sutures. The only known divergence from the relatively conservative nyctortherid body plan are the bizarre symbionts of Panesthiinae cockroaches, ciliates of the family Clevelandellidae, which forms a clade nested within the Nyctotheridae genus Nyctotherus. In this study we report another ciliate that diverges morphologically from the canonical Nyctotheridae body plan, and which is also found in Panesthiinae hosts. The novel ciliate Reductitherus cryptostomus n. gen., n. sp. differs from the rest of Nyctotheridae by absence of the anterior adoral groove, a shortened adoral zone completely enclosed in a notably small buccal cavity, and two strongly reduced kinetal sutures, one left anterodorsal and the other right posterodorsal.

Some Aspects of the Physiology of the Nyctotherus velox, a Commensal Ciliated Protozoon Taken from the Hindgut of the Tropical Millipede Archispirostreptus gigas

In this paper, the growth requirements, fermentation pattern, and hydrolytic enzymatic activities of anaerobic ciliates collected from the hindgut of the African tropical millipede Archispirostreptus gigas are described. Single-cell molecular analysis showed that ciliates from the millipede hindgut could be assigned to the Nyctotherus velox and a new species named N. archispirostreptae n. sp. The ciliate N. velox can grow in vitro with unspecified prokaryotic populations and various plant polysaccharides (rice starch-RS, xylan, crystalline cellulose20-CC, carboxymethylcellulose-CMC, and inulin) or without polysaccharides (NoPOS) in complex reduced medium with soluble supplements (peptone, glucose, and vitamins). Specific catalytic activity (nkat/g of protein) of α amylase of 300, xylanase of 290, carboxymethylcellulase of 190, and inulinase of 170 was present in the crude protein extract of N. velox. The highest in vitro dry matter digestibility was observed in RS and inulin after 96 h of fermentation. The highest methane concentration was observed in xylan and inulin substrates. The highest short-chain fatty acid concentration was observed in RS, inulin, and xylan. In contrast, the highest ammonia concentration was observed in NoPOS, CMC, and CC. The results indicate that starch is the preferred substrate of the N. velox. Hydrolytic enzyme activities of N. velox showed that the ciliates contribute to the fermentation of plant polysaccharides in the gut of millipedes.

DNA barcoding and coalescent-based delimitation of endosymbiotic clevelandellid ciliates (Ciliophora: Clevelandellida): a shift to molecular taxonomy in the inventory of ciliate diversity in panesthiine cockroaches

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 boundaries, the phylogenetic information contained in the rDNA cistron of clevelandellid ciliates, which had been isolated from the digestive tract of blaberid cockroaches, was studied using a multifaceted statistical approach. Multigene phylogenies revealed that the genus Clevelandella is paraphyletic containing members of the genus Paraclevelandia. To resolve the paraphyly of Clevelandella, two new genera, Anteclevelandella gen. nov. and Rhynchoclevelandella gen. nov., are proposed based on morphological synapomorphies and shared molecular characters. Multigene analyses and Bayesian species delimitation supported the existence of 13 distinct species within the family Clevelandellidae, eight of which represent new taxa. Moreover, two new Nyctotherus species were recognized within the clade that is sister to the Clevelandellidae. According to the present distance and network analyses, the first two domains of the 28S rRNA gene showed much higher power for species discrimination than the 18S rRNA gene and ITS region. Therefore, the former molecular marker was proposed to be a suitable group-specific barcode for the family Clevelandellidae.

Macroevolutionary analyses of ciliates associated with hosts support high diversification rates

Ciliophora is a phylum that is comprised of extremely diverse microorganisms with regard to their morphology and ecology. They may be found in various environments, as free-living organisms or associated with metazoans. Such associations range from relationships with low metabolic dependence such as epibiosis, to more intimate relationships such as mutualism and parasitism. We know that symbiotic relationships occur along the whole phylogeny of the group, however, little is known about their evolution. Theoretical studies show that there are two routes for the development of parasitism, yet few authors have investigated the evolution of these characteristics using molecular tools. In the present study, we inferred a wide dated molecular phylogeny, based on the 18S rDNA gene, for the entire Ciliophora phylum, mapped life habits throughout the evolutionary time, and evaluated whether symbiotic relationships were linked to the variation in diversification rates and to the mode of evolution of ciliates. Our results showed that the last common ancestor for Ciliophora was likely a free-living organism, and that parasitism is a recent adaptation in ciliates, emerging more than once and independently via two distinct routes: (i) a free-living ciliate evolved into a mutualistic organism and, later, into a parasitic organism, and (ii) a free-living ciliate evolved directly into a parasitic organism. Furthermore, we have found a significant increase in the diversification rate of parasitic and mutualistic ciliates compared with their free-living conspecifics. The evolutionary success in different lineages of symbiont ciliates may be associated with many factors including type and colonization placement on their host, as well as physical and physiological conditions made available by the hosts.

Morphological and molecular characterization of a new ciliate Nyctotheroides grimi n. sp. (Armophorea, Clevelandellida) from Chinese frogs

A new species of clevelandellid ciliate, Nyctotheroides grimi n. sp., is described from the frog Fejervarya limnocharis. Light and scanning electron microscopy were used for the morphological studies, and the DNA encoding the SSU rRNA gene (SSU rDNA) and the ITS1-5.8S subunit rRNA-ITS2 region (ITS) were sequenced for genetic comparisons and phylogenetic analysis. The main distinctive morphological feature is a knob-like projection in the left-posterior end; other differential characters are the cell size, the length of the oral groove and the shape of the infundibulum. Nyctotheroides grimi possess an apical suture line in the left and right side of the anterior end and in the left side of the caudal end. In the phylogenetic analyses, the new species engroups with other Nyctotheroides species forming a monophyletic group. The high similarity in the SSU rDNA and ITS sequences between Nyctotheroides species suggests a relative recent divergence. The genetic data and the different host range support the separation of Nyctotheroides and Nyctotherus; however the morphological criterion based on the presence (in Nyctotheroides)/absence (in Nyctothterus) of an apical kinetal suture line should be modified to consider the presence of kinetal suture lines in the apical and/or the caudal left side in Nyctotheroides.

Phylogenetic position of Nyctotherus teleacus isolated from a tortoise (Astrochelys radiata) and its electron microscopic features

A commensal ciliate was isolated from the stool of a tortoise (Astrochelys radiata). The ciliate was classified as Nyctotherus teleacus, according to its basic morphological features. Electron microscopic observations using cultured N. teleacus (NictoT1 strain) revealed many spherical hydrogenosomes and methanogen-suspected bacteria, together with a characteristic triangular macronucleus containing many spherical chromosomes in the cytoplasm of NictoT1. The results of phylogenetic analysis showed that NictoT1 was included in the cluster of Nyctotheroides spp. (family Nyctotheridae). Nyctotheroides spp. commonly infest amphibians, which are taxonomically closely related to reptiles, including the tortoises evaluated in the present study.

Two New Endozoic Ciliates, Clevelandella lynni sp. n. and Nyctotherus galerus sp. n., Isolated from the Hindgut of the Wood-feeding Cockroach Panesthia angustipennis (Illiger, 1801)

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 characterized by a prominent peristomial projection, a notched left body margin, a tear-shaped to broadly ovoidal macronucleus, a karyophore attached to the right body margin, and by an adoral zone composed of on average 48 membranelles and extending about 51% of body length. The diagnostic features of N. galerus include a short posterior body projection, a spherical to broadly ellipsoidal macronucleus, a karyophore attached to the right and left body margins, refractile bodies densely packed anterior to the macronucleus, and an adoral zone composed of on average 57 membranelles and extending about 70% body length. The order Clevelandellida was consistently depicted as monophyletic in 18S rRNA gene phylogenies. Nyctotherus galerus was placed in the paraphyletic family Nyctotheridae, as sister taxon to all other Nyctotherus and Clevelandella species isolated from cockroaches. Clevelandella lynni fell in the monophyletic family Clevelandellidae, as sister taxon to C. panesthiae KC139718 but with very poor statistical support.

Delimitation of five astome ciliate species isolated from the digestive tube of three ecologically different groups of lumbricid earthworms, using the internal transcribed spacer region and the hypervariable D1/D2 region of the 28S rRNA gene

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 hypervariable D1/D2 region of the 28S rRNA gene have proven to be useful tools for the delimitation of species boundaries in closely related free-living ciliate taxa. In the present study, the power of these molecular markers as well as of the secondary structure of the ITS2 molecule were tested for the first time in order to discriminate the species of endosymbiotic ciliates that were isolated from the gastrointestinal tract of three ecologically different groups of lumbricid earthworms.

Results

Nineteen new ITS1–5.8S-ITS2 region and D1/D2-28S rRNA gene sequences were obtained from five astome species (Anoplophrya lumbrici, A. vulgaris, Metaradiophrya lumbrici, M. varians, and Subanoplophrya nodulata comb. n.), which were living in the digestive tube of three ecological groups of earthworms. Phylogenetic analyses of the rRNA locus and secondary structure analyses of the ITS2 molecule robustly resolved their phylogenetic relationships and supported the distinctness of all five species, although previous multivariate morphometric analyses were not able to separate congeners in the genera Anoplophrya and Metaradiophrya. The occurrence of all five taxa, as delimited by molecular analyses, was perfectly correlated with the ecological groups of their host earthworms.

Conclusions

The present study indicates that morphology-based taxonomy of astome ciliates needs to be tested in the light of molecular and ecological data as well. The use of morphological identification alone is likely to miss species that are well delimited based on molecular markers and ecological traits and can lead to the underestimation of diversity and overestimation of host range. An integrative approach along with distinctly increased taxon sampling would be helpful to assess the consistency of the eco-evolutionary trend in astome ciliates.

Living morphology and molecular phylogeny of oligohymenophorean ciliates associated with freshwater turbellarians

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 from the highly diverse class Oligohymenophorea, were detected: Haptophrya planariarum from the subclass Astomatia, Urceolaria mitra from the subclass Peritrichia, and Tetrahymena sp. from the subclass Hymenostomatia. Each of these ciliates is specialized for different parts of the turbellarian bodies: H. planariarum lives in the pharynx and rami of the intestine, U. mitra colonizes the body surface, and Tetrahymena sp. attacks open wounds and feeds on the mesenchyme. Astomes and peritrichs isolated from turbellarians are placed deeper in 18S rRNA gene phylogenies than their relatives isolated from annelids and mollusks. On the other hand, Tetrahymena sp. isolated from turbellarians is classified comparatively deeply within the family Tetrahymenidae, suggesting that the phylogeny of tetrahymenids does not correlate with that of their obligate/facultative host groups. Nevertheless, the reconstruction of ancestral traits corroborated the hypothesis that histophagy was already a life history trait of the progenitor of the subclass Hymenostomatia to which Tetrahymena belongs.

Co-existence of multiple bacterivorous clevelandellid ciliate species in hindgut of wood-feeding cockroaches in light of their prokaryotic consortium

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 interaction-adjusted index showed a very clear separation of the hindgut ciliate samples from the ciliate-free hindgut samples. This division was corroborated also by SparCC analysis which revealed strong negative associations between prokaryotic taxa that were relatively more abundant in the ciliate-free hindgut samples and prokaryotic taxa that were more abundant in the ciliate samples. This very likely reflects the grazing behaviour of hindgut ciliates which prefer Proteobacteria, Firmicutes and Actinobacteria, causing their abundances to be increased in the ciliate samples at the expense of abundances of Euryarchaeota and Bacteroidetes which prevail in the hindgut content. Ciliate species do not distinctly differ in the associated prokaryotes, indicating that minute variations in the proportion of associated bacteria might be sufficient to avoid competition between bacterivorous ciliate species and hence enable their co-occurrence in the same host. The nearest free-living relatives of hindgut ciliates have a different pattern of associations with prokaryotes, i.e., alphaproteobacteria are predominantly associated with free-living ciliates while gammaproteobacteria with hindgut ciliates.

Overlapping Community Compositions of Gut and Fecal Microbiomes in Lab-Reared and Field-Collected German Cockroaches

German cockroaches, Blattella germanica (Blattodea: Ectobiidae), are human commensals that move freely between food and waste, disseminating bacteria, including potential pathogens, through their feces. However, the relationship between the microbial communities of the cockroach gut and feces is poorly understood. We analyzed the V4 region of the 16S rRNA gene and the V9 region of the 18S rRNA gene by next-generation sequencing (NGS) to compare the bacterial and protist diversities in guts versus feces and males versus females, as well as assess variation across cockroach populations. Cockroaches harbored a diverse array of bacteria, and 80 to 90% of the operational taxonomic units (OTUs) were shared between the feces and gut. Lab-reared and field-collected cockroaches had distinct microbiota, and whereas lab-reared cockroaches had relatively conserved communities, considerable variation was observed in the microbial community composition of cockroaches collected in different apartments. Nonetheless, cockroaches from all locations shared some core bacterial taxa. The eukaryotic community in the feces of field-collected cockroaches was found to be more diverse than that in lab-reared cockroaches. These results demonstrate that cockroaches disseminate their gut microbiome in their feces, and they underscore the important contribution of the cockroach fecal microbiome to the microbial diversity of cockroach-infested homes.IMPORTANCE The German cockroach infests diverse human-built structures, including homes and hospitals. It produces potent allergens that trigger asthma and disseminates opportunistic pathogens in its feces. A comprehensive understanding of gut and fecal microbial communities of cockroaches is essential not only to understand their contribution to the biology of the cockroach, but also for exploring their clinical relevance. In this study, we compare the diversity of bacteria and eukaryotes in the cockroach gut and feces and assess the variation in the gut microbiota across cockroach populations.

Sicuophora (Syn. Wichtermania) multigranularis from Quasipaa spinosa (Anura): morphological and molecular study, with emphasis on validity of Sicuophora (Armophorea, Clevelandellida)

Morphological studies of Sicuophora (Syn. Wichtermania) multigranularis Xiao et al., 2002, from the rectum of the frog, Quasipaa spinosa, performed using silver impregnation and scanning electron microscopy, confirmed the following newly recognized features: (1) only one apical suture on the right surface; (2) two naked regions at the posterior end of both the left and the right side of the body. Phylogenetic analysis based on the SSU-rRNA gene showed that S. multigranularis is a sister to a clade comprising all other Clevelandellida, strongly supporting the validity of the genus Sicuophora. This is also the first molecular data obtained for the genus Sicuophora. Because of the lack of molecular data, it will be necessary to obtain more genetic data from the family Sicuophoridae to discuss the question of the taxonomic status of the genus Sicuophora.

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

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.

Supplemental description of Nyctotheroides pyriformis n. comb. (=Macrocytopharynxa pyriformis (Nie, 1932) Li et al. 2002) from frog hosts with consideration of the validity of the genus Macrocytopharynxa (Armophorea, Clevelandellida)

The morphological revisions of Macrocytopharynxa pyriformis (Nie, 1932) Li et al., 2002; collected from the rectum of Fejervarya limnocharis (=Rana limnocharis), are presented in this paper: (1) two surfaces of the organism are not identical - left side narrower and convex, right broader and flat or slightly concave; (2) infundibulum is large and well-developed with no "fold" or "plicature" present in the middle or posterior portion; (3) micronucleus is tiny and ovoid shaped and always embedded in the middle concavity of macronucleus, which can be well revealed by ammoniacal silver staining. Our phylogenetic analysis based on SSU-rDNA showed that M. pyriformis fell into the Nyctotheroides clade, within which four definite Nyctotheroides species were involved - N. cordiformis, N. deslierresae, N. parvus and N. hubeiensis. In combination with their morphological features, we discussed the reliability of using karyophore organelles or kinetal suture patterns as the generic taxonomic criteria. Besides, we considered that the genus Macrocytopharynxa is a junior synonym of Nyctotheroides and we transfer its type species to Nyctotheroides as Nyctotheroides pyriformis n. comb. The phylogenetic pattern of the family Nyctotheridae was also indicated in our work, but it will be necessary to analyze more species from fishes and reptiles before coming to a sound conclusion.

Morphology of Nyctotheroides hubeiensis Li et al. 1998 from Frog Hosts with Molecular Phylogenetic Study of Clevelandellid Ciliates (Armophorea, Clevelandellida)

The morphology of Nyctotheroides hubeiensis (Acta Hydrobiol. Sin. 1998, 22(suppl.):187), collected from the rectum of Phelophylax nigromaculatus, is presented in this paper based on detailed morphological information and molecular data. Our phylogenetic analysis showed that N. hubeiensis fell into the Nyctotheroides clade, which was strongly supported as monophyletic and clustered as basal to the genera Nyctotherus and Clevelandella. Also, the monophyly of the Order Clevelandellida and the affinity of parasitic nyctotherids and free-living metopids were indicated in our work. The origin of clevelandellid ciliates as well as their possible evolutionary history was also discussed here; however, the analysis of more species from other vertebrate hosts (fish, reptiles) should be made before a well-supported conclusion can be drawn.

Gut Bacterial Community of the Xylophagous Cockroaches Cryptocercus punctulatus and Parasphaeria boleiriana

Cryptocercus punctulatus and Parasphaeria boleiriana are two distantly related xylophagous and subsocial cockroaches. Cryptocercus is related to termites. Xylophagous cockroaches and termites are excellent model organisms for studying the symbiotic relationship between the insect and their microbiota. In this study, high-throughput 454 pyrosequencing of 16S rRNA was used to investigate the diversity of metagenomic gut communities of C. punctulatus and P. boleiriana, and thereby to identify possible shifts in symbiont allegiances during cockroaches evolution. Our results revealed that the hindgut prokaryotic communities of both xylophagous cockroaches are dominated by members of four Bacteria phyla: Bacteroidetes, Firmicutes, Proteobacteria, and Actinobacteria. Other identified phyla were Spirochaetes, Planctomycetes, candidatus Saccharibacteria (formerly TM7), and Acidobacteria, each of which represented 1–2% of the total population detected. Community similarity based on phylogenetic relatedness by unweighted UniFrac analyses indicated that the composition of the bacterial community in the two species was significantly different (P < 0.05). Phylogenetic analysis based on the characterized clusters of Bacteroidetes, Spirochaetes, and Deltaproteobacteria showed that many OTUs present in both cockroach species clustered with sequences previously described in termites and other cockroaches, but not with those from other animals or environments. These results suggest that, during their evolution, those cockroaches conserved several bacterial communities from the microbiota of a common ancestor. The ecological stability of those microbial communities may imply the important functional role for the survival of the host of providing nutrients in appropriate quantities and balance.

A molecular survey of Australian and North American termite genera indicates that vertical inheritance is the primary force shaping termite gut microbiomes

BACKGROUND

Termites and their microbial gut symbionts are major recyclers of lignocellulosic biomass. This important symbiosis is obligate but relatively open and more complex in comparison to other well-known insect symbioses such as the strict vertical transmission of Buchnera in aphids. The relative roles of vertical inheritance and environmental factors such as diet in shaping the termite gut microbiome are not well understood.

RESULTS

The gut microbiomes of 66 specimens representing seven higher and nine lower termite genera collected in Australia and North America were profiled by small subunit (SSU) rRNA amplicon pyrosequencing. These represent the first reported culture-independent gut microbiome data for three higher termite genera: Tenuirostritermes, Drepanotermes, and Gnathamitermes; and two lower termite genera: Marginitermes and Porotermes. Consistent with previous studies, bacteria comprise the largest fraction of termite gut symbionts, of which 11 phylotypes (6 Treponema, 1 Desulfarculus-like, 1 Desulfovibrio, 1 Anaerovorax-like, 1 Sporobacter-like, and 1 Pirellula-like) were widespread occurring in ≥50% of collected specimens. Archaea are generally considered to comprise only a minority of the termite gut microbiota (<3%); however, archaeal relative abundance was substantially higher and variable in a number of specimens including Macrognathotermes, Coptotermes, Schedorhinotermes, Porotermes, and Mastotermes (representing up to 54% of amplicon reads). A ciliate related to Clevelandella was detected in low abundance in Gnathamitermes indicating that protists were either reacquired after protists loss in higher termites or persisted in low numbers across this transition. Phylogenetic analyses of the bacterial communities indicate that vertical inheritance is the primary force shaping termite gut microbiota. The effect of diet is secondary and appears to influence the relative abundance, but not membership, of the gut communities.

CONCLUSIONS

Vertical inheritance is the primary force shaping the termite gut microbiome indicating that species are successfully and faithfully passed from one generation to the next via trophallaxis or coprophagy. Changes in relative abundance can occur on shorter time scales and appear to be an adaptive mechanism for dietary fluctuations.

Physicochemical conditions, metabolites and community structure of the bacterial microbiota in the gut of wood-feeding cockroaches (Blaberidae: Panesthiinae)

While the gut microbiota of termites and its role in symbiotic digestion have been studied for decades, little is known about the bacteria colonizing the intestinal tract of the distantly related wood-feeding cockroaches (Blaberidae: Panesthiinae). Here, we show that physicochemical gut conditions and microbial fermentation products in the gut of Panesthia angustipennis resemble that of other cockroaches. Microsensor measurements confirmed that all gut compartments were anoxic at the center and had a slightly acidic to neutral pH and a negative redox potential. While acetate dominated in all compartments, lactate and hydrogen accumulated only in the crop. The high, hydrogen-limited rates of methane emission from living cockroaches were in agreement with the restriction of F420-fluorescent methanogens to the hindgut. The gut microbiota of both P. angustipennis and Salganea esakii differed strongly between compartments, with the highest density and diversity in the hindgut, but similarities between homologous compartments of both cockroaches indicated a specificity of the microbiota for their respective habitats. While some lineages were most closely related to the gut microbiota of omnivorous cockroaches and wood- or litter-feeding termites, others have been encountered also in vertebrates, reinforcing the hypothesis that strong environmental selection drives community structure in the cockroach gut.

Phylogenetic study of Class Armophorea (Alveolata, Ciliophora) based on 18S-rDNA data

The 18S rDNA phylogeny of Class Armophorea, a group of anaerobic ciliates, is proposed based on an analysis of 44 sequences (out of 195) retrieved from the NCBI/GenBank database. Emphasis was placed on the use of two nucleotide alignment criteria that involved variation in the gap-opening and gap-extension parameters and the use of rRNA secondary structure to orientate multiple-alignment. A sensitivity analysis of 76 data sets was run to assess the effect of variations in indel parameters on tree topologies. Bayesian inference, maximum likelihood and maximum parsimony phylogenetic analyses were used to explore how different analytic frameworks influenced the resulting hypotheses. A sensitivity analysis revealed that the relationships among higher taxa of the Intramacronucleata were dependent upon how indels were determined during multiple-alignment of nucleotides. The phylogenetic analyses rejected the monophyly of the Armophorea most of the time and consistently indicated that the Metopidae and Nyctotheridae were related to the Litostomatea. There was no consensus on the placement of the Caenomorphidae, which could be a sister group of the Metopidae + Nyctorheridae, or could have diverged at the base of the Spirotrichea branch or the Intramacronucleata tree.