Insights into the phylogeny of sporadotrichid ciliates (Protozoa, Ciliophora: Hypotricha) based on genealogical analyses of multiple molecular markers

The sporadotrichid ciliates are an especially diverse group. A number of investigators have studied the morphological, morphogenetic, and molecular relationships among members of this group. Despite this, a consistent classification is still lacking and several important questions about the phylogenetic relationships within this group remain unsolved. To improve our understanding of these relationships, we constructed phylogenetic trees using the nucleotide sequences of the small-subunit rRNA (SSrRNA) gene and amino acid sequences of actin I and α-tubulin. Analyses of SSrRNA gene sequences indicated that: 1) the Sporadotrichida sensu Lynn (2008) and the Oxytrichidae are polyphyletic; 2) the Uroleptus species, which are classified to urostylids, formed a sister group with the oxytrichids; 3) Halteria grandinella, which is grouped morphologically with oligotrich species, clustered within the oxytrichids. These results are congruent with previous studies based on SSrRNA gene sequences. However, the amino acid sequences of actin I and α-tubulin yielded different topologies. The main results are: 1) in all phylogenetic trees, the genus Oxytricha was paraphyletic; 2) Uroleptus was sister to a subset of Urostyla and Holosticha, albeit with low supporting values; 3) Halteria grandinella was separated distantly from the Oxytrichidae in trees inferred from actin I amino acid sequences but clustered with oligotrichids in the α-tubulin analysis. The inconsistency among the trees inferred from these different molecular markers may be caused by rapidly accumulated genetic characterizations of ciliates. Further studies with additional molecular markers and sampling of more taxa are expected to better address the relationships among sporadotrichids.

Molecular Phylogenetic Lineage of Plagiopogon and Askenasia(Protozoa, Ciliophora) Revealed by Their Gene Sequences

Prostomates and haptorians are two basal groups of ciliates with limited morphological characteristics available for taxonomy. Morphologically, the structures used to identify prostomates and haptorians are similar or even identical, which generate heavy taxonomic and phylogenetic confusion. In present work, phylogenetic positions lineage of two rare genera, Plagiopogon and Askenasia, were investigated. Three genes including small subunit ribosomal RNA gene(hereafter SSU r DNA), internal transcribed spacer region(ITS region), and large subunit ribosomal RNA gene(LSU r DNA) were analyzed, 10 new sequences five species each. Our findings included 1) class Prostomatea and order Haptorida are multiphyletic; 2) it may not be appropriate to place order Cyclotrichiida in subclass Haptoria, and the systematic lineage of order Cyclotrichiida needs to be verified further; 3) genus Plagiopogon branches consistently within a clade covering most prostomes and is basal of clade Colepidae, implying its close lineage to Prostomatea; and 4) Askenasia is phylogenetically distant from the subclass Haptoria but close to classes Prostomatea, Plagiopylea and Oligohymenophorea. We supposed that the toxicyst of Askenasia may be close to taxa of prostomes instead of haptorians, and the dorsal brush is a more typical morphological characteristics of haptorians than toxicysts.

Morphological and molecular examination of the ciliate family Lagynusidae(Protista,Ciliophora,Prostomatea)with descriptions of two new genera and two new species from China

Ciliates in the class Prostomatea play an important role in the global microbial loop due to their signifcant abundances and broad feeding strategies at the foundation of food webs.Despite their importance in ecosystems,the taxonomy and systematics of this group of ciliates has long been poorly understood,with this being especially true for members of the family Lagynusidae.Here we examine four lagynusids collected from sandy beaches in China,using silver-staining and 18S rRNA gene sequencing techniques.These investigations revealed two new genera and two new species and provided details for two little known forms:Penardella marina gen.nov.,sp.nov.,Apolagynus cucumis(as reported by Penard.Études sur les infusoires d’eau douce.Georg and Cie,Genève,1922)gen.nov.,comb.nov.,Lagynus minutus sp.nov.,and Lagynus elegans(Engelmann in Z Wiss Zool 11:347-393,1862)Quennerstedt(Acta Univ Lund 4:1-48,1867).Penardella gen.nov.can be morphologically distinguished by having more than three dikinetidal perioral kineties.Apolagynus gen.nov.difers from the closely related genus Lagynus in the absence of a conspicuous neck-like region.The ciliature of Apolagynus cucumis is revealed here for the frst time,which demonstrates the classifcation of this species within Lagynusidae.Furthermore,Apolagynus binucleatus(Jiang et al.,2021)comb.nov.is established according to the new fnding.The results of our phylogenetic analyses based on the 18S rRNA gene support the establishment of two new genera and indicate that Lagynusidae is monophyletic,which further strengthens its valid taxonomic status.

Phylogeny of the anaerobic ciliate genus Sonderia(Protista:Ciliophora:Plagiopylea),including the description of three novel species and a brief revision of the genus

Anaerobic protists in general,and ciliates in particular,are important components of anoxic or hypoxic environments,however,their diversity remains underestimated.Sonderia is a poorly studied genus that is distributed worldwide and is commonly found in anaerobic environments.In the present study,the taxonomy and phylogeny of three new species,namely Sonderia aposinuata sp.nov.,Sonderia paramacrochilus sp.nov.and Sonderia steini sp.nov.,collected from China,were investigated based on microscopic observations and SSU rRNA gene sequencing methods.Sonderia aposinuata sp.nov.is diagnosed mainly by having a relatively large body size,a crescent-shaped oral opening,numerous slender extrusomes,one suture on the ventral side and two on the dorsal side,and a buccal cavity that occupies the anterior third of the cell.Sonderia paramacrochilus sp.nov.closely resembles S.macrochilus but differs mainly by its oral opening being located closer to the anterior cell margin and its spindle-shaped extrusomes.Sonderia steini sp.nov.is a freshwater species that can be recognized by its shallow buccal cavity,sparsely distributed rod-shaped extrusomes,and having 68–79 monokinetidal somatic kineties that form sutures on both sides of the body.Phylogenetic analyses based on small subunit ribosomal RNA(SSU rRNA)gene sequence data support the monophyly of the family Sonderiidae,however,Sonderia is paraphyletic.The genus Sonderia is briefly revised and a key to the identification of species belonging to this genus is supplied.

Doublets of the unicellular organism Euplotes vannus(Alveolata,Ciliophora,Euplotida):the morphogenetic patterns of the ciliary and nuclear apparatuses associated with cell division

Ciliated protists are one of the most diverse and highly differentiated group among unicellular organisms.Doublets occur in ciliates when two cells fuse into a single individual.Doublets contain two major cellular components(either cell in a doublet)and have traditionally been considered as developmental anomalies.Nevertheless,doublets can divide or even conjugate effectively,which may represent dispersal forms of the life stages.In addition,morphogenesis,as an important process in the life cycle,will provide important insights into the complex differentiation mechanism and various physiological phenomena.However,morphogenetic studies focusing on doublets of ciliates are very limited,which has become an obstacle to understand their complete life history.Here we isolated a doublet strain from the marine species Euplotes vannus(Müller,1786)Diesing,1850 and investigated its morphogenetic events during asexual reproduction.Our results indicate that:(1)the opisthe’s oral primordium develops de novo beneath the cortex;(2)the frontoventral and transverse cirral anlagen,cirrus I/1,and marginal anlagen in both dividers develop de novo separately;(3)the dorsal kinety anlagen,the three rightmost ones of which produce three caudal cirri for the proter,occur within the parental structures in the mid-body region;(4)the opisthe acquires two caudal cirri,one from the end of each two rightmost kineties;and(5)there are two macronuclei and one micronucleus in the doublet and they divide amitotically and mitotically,respectively.Finally,we speculate that this special differentiation may be an adaptive form to adverse environments.

Ontogenesis and systematic position of a new hypotrichous ciliate,Chaetospira sinica sp.nov.,with an improved diagnosis of the poorly defined family Chaetospiridae Jankowski,1985(Protozoa,Ciliophora,Hypotrichia)

Ciliates are unique single-celled organisms that play important roles in ecological,environmental,evolutionary,and ontogenetic research.In the present study,phylogenetic analyses based on 18S rRNA gene sequence data reveal that Chaetospira sinica sp.nov.clusters with Stichotricha aculeata with strong to full support(97%ML,1.00 BI),but is not closely related to members of Spirofilidae Gelei,1929 to which Chaetospira and Stichotricha have previously been assigned.Phylogenetic analyses,together with morphological and morphogenetic data from Chaetospira sinica sp.nov.,support the validity of family Chaetospiridae Jankowski,1985.Chaetospira and Stichotricha are here assigned to the family Chaetospiridae,the improved diagnosis of which is as follows:non-dorsomarginalian Hypotrichia with flask-shaped body;oral region extending along narrow anterior neck region;lorica usually present;two ventral and two marginal cirral rows,all distinctly spiraled or obliquely curved;pretransverse and transverse cirri absent.The basic morphogenetic features in C.sinica sp.nov.can be summarized as:(1)the oral primordium for the opisthe develops de novo and the parental adoral zone is completely retained by the proter;(2)all ventral cirral anlagen and marginal anlagen developed intrakinetally;(3)three dorsal kineties anlagen formed intrakinetally in each daughter cell;and(4)macronuclear nodules fuse into a single mass.Exconjugant cells were also isolated and their morphologic and molecular data are provided.