Morphological Characterizations of Four Species of Parallelostrombidium (Ciliophora, Oligotrichia), with a Note on the Phylogeny of the Genus

Abstract

The morphology and phylogeny of four oligotrichid ciliates, Parallelostrombidium paraellipticum sp. n., P. dragescoi sp. n., P. jankowskii (Xu et al. 2009) comb. n., and P. kahli (Xu et al. 2009) comb. n., are described or redescribed based on live observation, protargol stained material, and SSU rRNA gene sequences. The new species P. paraellipticum sp. n. is characterized by its obovoidal cell shape, adoral zone composed of 17-21 collar, 9-11 buccal, and two thigmotactic membranelles, and extrusomes attached in one row along the girdle kinety. The new species P. dragescoi sp. n. is distinguished from its congeners by its obovoidal cell shape and a lack of thigmotactic membranelles. Based on ciliary patterns recognizable in the original slides, Omegastrombidium jankowskii Xu et al. 2009 and O. kahli Xu et al. 2009 should be transferred to the genus Parallelostrombidium Agatha 2004. Phylogenetic analyses based on SSU rRNA gene sequence data demonstrate that all four new sequences cluster with previously described congeners. The genus Parallelostrombidium is separated into two clusters, suggesting its non-monophyly and probably corresponding to the two subgenera proposed by Agatha and Strüder-Kypke (2014), as well as their morphological difference (cell dorsoventrally flattened vs. unflattened).

Progress in studies on the diversity and distribution of planktonic ciliates (Protista, Ciliophora) in the South China Sea

“…There remains a need for taxonomy work. Although many new planktonic ciliate taxa have been reported in the SCS, the species number continues to increase, demonstrating that the diversity of these ciliates is higher than previously supposed (Bai et al 2020a;Hu et al 2019;Liu et al 2017;Song et al 2018a). Moreover, due to the lack of necessary taxonomy data, such as morphological and molecular markers, for many rare species, an accurate species-level identification cannot be achieved in most community studies.…”

Two Anaerobic Ciliates (Ciliophora, Armophorea) from China: Morphology and SSU rDNA Sequence, with Report of a New Species, Metopus paravestitus nov. spec

“…TaKaRa ExTaq polymerase (TaKaRa Biomedicals, Shiga, Japan) was used to amplify the SSU rDNA with the universal eukaryotic primers, EukA and EukB, (Medlin et al 1988). PCR amplification, cloning, and sequencing were performed according to Song et al (2018).…”

Further analyses on the evolutionary “key‐protist”Halteria(Protista, Ciliophora) based on transcriptomic data

“…They are characterized mainly by the globular body shape, reduced somatic ciliature (cirrus-like "bristles" used for performing conspicuous jumps), apical adoral structure (with the "collar" as an "open" circle) and enantiotropic cell division mode (the cell axes of proter and opisthe not oriented in the same direction, but in opposite orientation) (Figure 1) (Fauré-Fremiet, 1953;Foissner et al, 2007;Petz & Foissner, 1992;Song, 1992). All these characteristics are shared with high similarity with these in the oligotrichs (mostly globular, reduced somatic ciliature and enantiotropic cell division) (Agatha, 2004;Liu et al, 2016;Petz & Foissner, 1992;Song et al, 2018), but differ from these in the hypotrichs (mostly dorsoventrally compressed, ventral cirri and synclastic cell division) ( Figure 1) (Chen, Zhao, Shao, Miao, & Clamp, 2017;Lu, Huang, Chen, & Berger, 2018;Luo et al, 2017Luo et al, , 2018. However, phylogenetic analyses based on small subunit ribosomal DNA (SSU rDNA), internal transcribed spacer (ITS), 5.8S rDNA, large subunit ribosomal DNA (LSU rDNA), α-tubulin and actin I genes have suggested that halteriids are closely related to oxytrichids, a highly specialized group of hypotrichs Hu et al, 2011;Lynn & Sogin, 1988;Paiva, Borges, Harada, & Silva-Neto, 2009).…”