Planktonic ciliate species form multiple trophic guilds and are central components of freshwater food webs. Progress in molecular analytical tools has opened new insight into ciliate assemblages. However, high and variable 18S rDNA copy numbers, typical for ciliates, make reliable quantification by amplicon sequencing extremely difficult. For an exact determination of abundances, the classical morphology-based quantitative protargol staining is still the method of choice. Morphotype analyses, however, are time consuming and need specific taxonomic expertise. Catalyzed reporter deposition fluorescence in situ hybridization (CARD-FISH) may represent a promising tool for the analysis of planktonic ciliates by combining molecular identification with microscopic quantification. We tested the applicability of CARD-FISH using nine cultured ciliate species. Eight species- and three genus-specific oligonucleotide probes were designed based on their 18S rRNA genes. The CARD-FISH protocol was adapted and the specificity of probes was established. We subsequently examined the precision of quantitation by CARD-FISH on single cultures and mock assemblages. Successful tests on lake water samples proved that planktonic ciliates could be identified and quantified in field samples by CARD-FISH. Double hybridizations allowed studying interspecific predator prey interactions between two ciliate species. In summary, we demonstrate that CARD-FISH with species-specific probes can facilitate studies on the population dynamics of closely related, small sized or cryptic species at high sampling frequencies.
- Keywords
- CARD-FISH, ciliate quantification, fluorescence in situ hybridization, lake water samples, planktonic ciliates, quantitative protargol staining,
- Publication type
- Journal Article MeSH
In this article we provide morphologic and morphometric data based on in vivo observation, protargol impregnation, scanning electron microscopy and an 18S rRNA gene sequence for another member of the genus Brachonella, Brachonella pulchra comb. nov. (basionym: Metopus pulcher Kahl, 1927). We also provide preliminary data on resting cyst structure and formation in Brachonella pulchra and discuss the possible taxonomic usefulness of these structures.
- Keywords
- 18S rRNA gene, Anaerobic ciliates, Metopus, Protargol impregnation, extrusome, phylogeny,
- MeSH
- Ciliophora classification MeSH
- Phylogeny * MeSH
- Microscopy, Electron, Scanning MeSH
- RNA, Ribosomal, 18S genetics MeSH
- Sequence Analysis, DNA MeSH
- Publication type
- Journal Article MeSH
- Names of Substances
- RNA, Ribosomal, 18S MeSH
Class Armophorea Lynn, 2004 includes two orders of mainly free-living anaerobic ciliates, Armophorida Jankowski, 1980 and Metopida Jankowski, 1980 and, a third, the exclusively endosymbiotic Clevelandellida. Kahl described the majority of free-living metopid species early in the 20th century. Excepting Jankowski in the 1960's, little further interest was shown in this group. Metopus turbo Dragesco and Dragesco-Kernéis, 1986, from a West African pond, was more recently described. Although not explicitly described as endemic, Dragesco believed in some degree of endemism of sub-Saharan ciliates. Our discovery of M. turbo on Guam, Micronesia was unexpected. Metopus turbo was identified by live observation, protargol impregnation, and scanning electron microscopy, providing reasonable evidence of conspecificity when compared with the original description. Outstanding morphologic features include the stout shape and transversely situated bandform macronucleus. The morphology of Metopus turbo differs markedly from that of the Metopus/Brachonella clade and is distant from Metopus es in phylogenetic analyses. The 18S rDNA sequence of the Guam M. turbo differs from that of M. es, type species of Metopus, by >8% and shows distinct morphologic differences from the genus Atopospira to which it is sister. These facts suggest that transfer to a new genus, Idiometopus gen. nov. is indicated.
- Keywords
- 18S rRNA gene., Armophorea, Metopida, anaerobic ciliates, phylogeny, protargol,
- MeSH
- Ciliophora classification isolation & purification ultrastructure MeSH
- Phylogeny MeSH
- Molecular Typing MeSH
- Fresh Water MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Geographicals
- Africa MeSH
- Guam MeSH
Oxymonads are a group of flagellates living as gut symbionts of insects or vertebrates. They have several unique features, one of them being the absence of mitochondria. Diversity of this group is seriously understudied, which is particularly true for small species from the family Polymastigidae. We isolated 34 strains of oxymonads with Polymastigidae-like morphology from 24 host species and unused cesspits and sequenced the SSU rRNA gene. Our strains formed two clades in the phylogenetic tree with Streblomastix strix branching between them. This topology was also supported by a three-gene phylogenetic analysis. Despite considerable genetic differences between the clades, light and electron microscopy revealed only subtle differences. The larger clade is considered genus Monocercomonoides and the isolates belonging here were classified into three new species (including the first potentially free-living species), two previously described species, and three unclassified lineages. The smaller clade, here described as Blattamonas gen. nov., consists of three newly described species. Concomitantly with the description of Blattamonas, we elevate the Monocercomonoides subgenus Brachymonas to the genus level. Our study shows that, despite their conserved morphology, the molecular diversity of Polymastigidae-like oxymonads is broad and represents a substantial part of the diversity of oxymonads.
Bothrostoma is a genus of anaerobic ciliates in family Metopidae comprising four species, all described based solely on the morphology of living and fixed cells. Unlike other metopids, cells of Bothrostoma are not twisted anteriorly, have a flattened preoral dome, a very prominent sail-like paroral membrane, and an adoral zone of distinctive, very narrow, curved membranelles confined to a wide, non-spiraling peristome on the ventral side. We examined 20 populations of Bothrostoma from hypoxic freshwater sediments. We provide morphological characterization and 18S rRNA gene sequences of four new species, namely B. bimicronucleatum sp. nov., B. boreale sp. nov., B. kovalyovi sp. nov., and B. robustum sp. nov., as well as B. undulans (type species), B. nasutum, and B. ovale comb. nov. (original combination Metopus undulans var. ovalis Kahl, 1932). Except for B. nasutum, Bothrostoma species show low genetic variability among geographically distant populations. Intraspecific phenotypic variability might be driven by environmental conditions. In phylogenetic analyses, Bothrostoma is not closely related to Metopus sensu stricto and forms a moderately supported clade with Planometopus, here referred to as BoPl clade. The anterior axial torsion of the body, typical of other Metopidae, appears to have been lost in the last common ancestor of the BoPl clade.
- Keywords
- 18S rRNA gene, Ciliates, Metopus, anoxia, phylogeny, protargol impregnation,
- MeSH
- Ciliophora * genetics MeSH
- Species Specificity MeSH
- Phylogeny MeSH
- RNA, Ribosomal, 18S genetics MeSH
- Fresh Water MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Names of Substances
- RNA, Ribosomal, 18S MeSH
The free-living ciliates of the order Metopida Jankowski, 1980 are pivotal players in the microbial food web of the sulfuretum, acting as hosts to prokaryotic endo- and ectosymbionts. They are also of interest in the study of the function and evolution of their mitochondrion-related organelle, the hydrogenosome. The taxonomy and phylogeny of this group remains confused, due, in large part, to the fact that most of its taxa have not been characterized by modern methods including molecular sequencing. In this report we provide morphologic and molecular characterization of seven taxa from the poorly-known resurrected genus Urostomides obtained in the course of broad geographic sampling. Foissner (2016) established the family Apometopidae to include Apometopus (a junior synonym of Urostomides) and Cirranter Jankowski, 1964. These two genera differ from all other metopid genera in having a four-rowed perizonal ciliary stripe, the only currently recognizable morphologic synapomorphy for the family. The members of Urostomides show remarkable morphologic diversity. The genus has a broad geographic distribution, occurring on six continents. Urostomides species form a strongly supported clade in phylogenetic analyses. Relationships within the genus itself are less clearly resolved. The diagnoses of Apometopidae and Urostomides are emended.
- Keywords
- 18S rRNA gene, Anaerobic ciliates, Cirranter, Metopida, Phylogeny, Protargol impregnation,
- MeSH
- Ciliophora classification cytology genetics MeSH
- Species Specificity MeSH
- Phylogeny * MeSH
- RNA, Ribosomal, 18S MeSH
- Publication type
- Journal Article MeSH
- Names of Substances
- RNA, Ribosomal, 18S MeSH
Karyorelictids are a group of ciliates inhabiting marine and freshwater biotopes and possessing a non-dividing macronucleus. We describe a new freshwater species based on morphology and the 18S rRNA gene sequence data. Loxodes tziscaensis n. sp. can be easily distinguished from other Loxodes species by the arrangement of the nuclear apparatus and features of the buccal and somatic ciliature. The current proposed 18S rRNA phylogeny of Loxodes, including seven Loxodes species, shows two morphologically well-supported groups. Group A (L. rostrum, type species; L. vorax and L. tziscaensis n. sp.) includes species with a single nuclear group (two macronuclei and one micronucleus), in contrast to species of group B, which possess more than one nuclear group (L. striatus, L. magnus, L. kahli, L. penardi, and L. rex). We propose that the last common ancestor of Loxodes was a marine Remanella-like species possessing a single nuclear group. The division and differentiation of the micronucleus into a new macronucleus and the retention of the old macronuclei, independently of cell division, may have been two crucial processes during the evolution and diversification of Loxodes species with one nuclear group into species with multiple nuclear groups.
- Keywords
- Loxodida, Non-dividing macronucleus, Nuclear dualism, Phylogeny, Protargol impregnation, Remanella,
- MeSH
- Ciliophora * genetics MeSH
- Phylogeny MeSH
- Macronucleus MeSH
- RNA, Ribosomal, 18S genetics MeSH
- Publication type
- Journal Article MeSH
- Review MeSH
- Geographicals
- Mexico MeSH
- Names of Substances
- RNA, Ribosomal, 18S MeSH
We report the discovery of three new species of freshwater metopid ciliates, Pileometopus lynni gen. et sp. nov., Castula flexibilis gen. et sp. nov., and Longitaenia australis gen. et sp. nov. Based on morphologic features and the 18S rRNA gene phylogeny, we transfer two known species of Metopus to the new genus Castula, as C. fusca (Kahl, 1927) comb. nov. and C. setosa (Kahl, 1927) comb. nov. and another known species is herein transferred to the new genus Longitaenia, as L. gibba (Kahl, 1927) comb. nov. Pileometopus is characterized by a turbinate body shape, a dorsal field of densely spaced dikinetids, a bipartite paroral membrane, and long caudal cilia. A distinctive morphologic feature of Castula species is long setae arising over the posterior third of the body (as opposed to a terminal tuft). Longitaenia spp. are characterized by an equatorial cytostome and long perizonal ciliary stripe relative to the cell length. Based on phylogenetic analyses of 18S rRNA gene sequences, we identify and briefly discuss strongly supported clades and intraspecific genetic polymorphism within the order Metopida.
- Keywords
- 18S rRNA gene., Armophorea, anaerobic ciliates, biogeography, phylogeny, protargol impregnation,
- MeSH
- Ciliophora classification cytology isolation & purification MeSH
- Phylogeny * MeSH
- Phylogeography MeSH
- RNA, Ribosomal, 18S genetics MeSH
- Fresh Water microbiology MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Names of Substances
- RNA, Ribosomal, 18S MeSH
Metopid ciliates occupy terrestrial, freshwater, and marine habitats worldwide, playing important roles as predominant consumers of bacteria, flagellates, algae, and diatoms in hypoxic environments. Metopus and Brachonella are the most species-rich metopid genera, however most of their species have not been studied by modern methods Here, we report the morphologic, morphometric and molecular characterization, and phylogeny of Metopus es and Brachonella contorta, both types of their respective genera, collected in a broad global sampling effort. Five strains of M. es and three strains of B. contorta were studied in detail, providing the first correlation of morphology, morphometrics, and 18S rRNA gene sequencing for both. We submitted 29 new 18S rRNA gene sequences to GenBank. Phylogenetic analyses yielded trees of similar topology. A strongly supported Metopus es clade is sister to the Brachonella contorta clade. Our analysis shows genus Metopus is not monophyletic. The monophyly of Brachonella cannot yet be determined due to lack of sequences for other species of this genus in molecular databases. Both species appear to have a global distribution. Metopus es was not found in Africa, probably reflecting low sampling effort. Strains of both species showed low 18S rRNA gene sequence divergence despite wide geographic separation.
- Keywords
- 18S rRNA gene, Anaerobic ciliates, Armophorida, Metopidae, Phylogeny, Protargol,
- MeSH
- Ciliophora classification cytology genetics MeSH
- Species Specificity MeSH
- Ecosystem MeSH
- Phylogeny * MeSH
- DNA, Protozoan genetics MeSH
- RNA, Ribosomal, 18S genetics MeSH
- Publication type
- Journal Article MeSH
- Names of Substances
- DNA, Protozoan MeSH
- RNA, Ribosomal, 18S MeSH
The research on anaerobic ciliates, to date, has mainly been focused on representatives of obligately anaerobic classes such as Armophorea or Plagiopylea. In this study, we focus on the anaerobic representatives of the subclass Scuticociliatia, members of the class Oligohymenophorea, which is mainly composed of aerobic ciliates. Until now, only a single anaerobic species, Cyclidium porcatum (here transferred to the genus Anaerocyclidium gen. nov.), has been described both molecularly and morphologically. Our broad sampling of anoxic sediments together with cultivation and single cell sequencing approaches have shown that scuticociliates are common and diversified in anoxic environments. Our results show that anaerobic scuticociliates represent a distinctive evolutionary lineage not closely related to the family Cyclidiidae (order Pleuronematida), as previously suggested. However, the phylogenetic position of the newly recognized lineage within the subclass Scuticociliatia remains unresolved. Based on molecular and morphological data, we establish the family Anaerocyclidiidae fam. nov. to accommodate members of this clade. We further provide detailed morphological descriptions and 18S rRNA gene sequences for six new Anaerocyclidium species and significantly broaden the described diversity of anaerobic scuticociliates.
