Historical Review of Studies on Cyrtophorian Ciliates (Ciliophora, Cyrtophoria) from China

Abstract

The subclass Cyrtophoria are a group of morphologically specialized ciliates which mainly inhabit soil, freshwater, brackish water, and marine environments. In this study, we revise more than 50 publications on the taxonomy, phylogeny, and ecology of cyrtophorian ciliates in China since the first publication in 1925, most of which were carried out in coastal areas. The research history can be divided into three periods: the early stage, the Tibet stage, and the molecular stage. To date, 103 morpho-species (147 isolates) have been formally recorded in China, with ciliature patterns described for 82 of them. A species checklist and an illustrated identification key to the genera are provided. A total of 100 small subunit rDNA sequences have been obtained for 74 taxonomic hits (lowest taxonomic rank to species or genus). These sequences are used for the study of molecular phylogeny. Based on these morphological data and molecular phylogeny analyses, we synthesize the understanding of the phylogeny of cyrtophorian ciliates. We hypothesize that the key evolutionary event of cyrtophorian ciliates lies in the separation of the stomatogenesis zone (postoral kineties) from the left kineties, namely, the formation of an independent “sexual organelle”. We, furthermore, briefly summarize the ecological features of cyrtophorian ciliates and provide a comprehensive bibliography of related research from China. Finally, we give an outlook on the future research directions of these taxa.

New contributions to the Cyrtophoria ciliates (Protista, Ciliophora): Establishment of new taxa and phylogenetic analyses using two ribosomal genes

“…The scale bar corresponds to 10 substitutions per 100 nucleotide positions. *Possible misidentification; # has been renamed Chilodonella apouncinata (Qu et al, 2022)…”

“…The scale bar corresponds to 10 substitutions per 100 nucleotide positions. *Possible misidentification; # has been renamed Chilodonella apouncinata (Qu et al, 2022) It is noteworthy that the mtSSU rRNA gene sequence of Derouxella lembodes sp. nov. is extremely unusual.…”

“…ciliate, Cyrtophoron, Derouxella gen. nov., molecular phylogeny, morphology modern taxonomical methods (e.g. Chen et al, 2012Chen et al, , 2018Deroux, 1976aDeroux, , 1976bDovgal & Grigorovich, 2001;Gong & Song, 2006;Hu et al, 2019;Jin et al, 2020;Ma et al, 2021;Pan et al, 2012Pan et al, , 2016Park & Min, 2014;Qu et al, 2021Qu et al, , 2022Wang et al, 2017Wang et al, , 2019Wang, Jiang, et al, 2021b). In terms of morphology, both the oral and the somatic ciliature exhibit very diverse patterns, which infers a high species diversity within this group.…”

“…Over the past three decades, several attempts have been made to explore the phylogeny within the Cyrtophoria Fauré‐Fremiet in Corliss, 1956, a subclass of Phyllopharyngea de Puytorac et al, 1974, based both on marker gene sequences and morphological characteristics (Chen et al, 2016; Gao et al, 2012; Leipe et al, 1994; Wang et al, 2017). The main findings of these studies include: (1) the monophyly of the Cyrtophoria is supported (Li & Song, 2006; Snoeyenbos‐West et al, 2004); (2) phylogenies derived from morphological characteristics and nSSU rRNA gene sequences are basically concordant (Gao et al, 2012; Qu et al, 2022; Wang et al, 2017); (3) confusions in some genera or families were resolved thus clarifying their phylogenetic relationships (Chen et al, 2016; Gao et al, 2012; Pan et al, 2017).…”

“…In the past two centuries a large number of phyllopharyngeans have been discovered, several of which have been recently described or redescribed using modern taxonomical methods (e.g. Chen et al, 2012, 2018; Deroux, 1976a, 1976b; Dovgal & Grigorovich, 2001; Gong & Song, 2006; Hu et al, 2019; Jin et al, 2020; Ma et al, 2021; Pan et al, 2012, 2016; Park & Min, 2014; Qu et al, 2021, 2022; Wang et al, 2017, 2019; Wang, Jiang, et al, 2021b). In terms of morphology, both the oral and the somatic ciliature exhibit very diverse patterns, which infers a high species diversity within this group.…”