Abstract
Ciliated protists (ciliates) are extremely diverse and play important ecological roles in almost all kinds of habitats. In this study, two new hypotrichs, Wilbertophrya sinica n. g. and n. sp. and Bakuella xianensis n. sp., from China are investigated. Wilbertophrya n. g. can be separated from related genera mainly by the combination of lacking a buccal cirrus, pretransverse cirri, and caudal cirri, while possessing frontoterminal cirri. Analyses based on morphological and molecular data confirm the validity of the species, W. sinica n. sp., which is characterized as follows: body 50–115 μm × 15–35 μm in vivo; midventral complex comprises four or five cirral pairs only and terminates above mid-body; three frontal, two frontoterminal cirri, and two to four transverse cirri; about 15 macronuclear nodules; colorless cortical granules sparsely distributed. Another new species, B. xianensis n. sp., was isolated from a freshwater wetland and is defined as follows: body 115–150 μm × 40–65 μm in vivo; about 70 macronuclear nodules; dark-brownish cortical granules in groups; midventral complex comprises 8–12 cirral pairs forming a row that terminates posteriorly in mid-body region and two or three short midventral rows that are continuous with the row of midventral pairs; three frontal, four to six frontoterminal, and three to five fine transverse cirri; three bipolar dorsal kineties. Phylogenetic analyses based on small subunit ribosomal DNA (SSU rDNA) sequence data suggest that the new genus Wilbertophrya n. g. belongs to an isolated clade, which might represent an undescribed taxon at the family level, whereas B. xianensis n. sp. groups with several congeners and members of other related genera are within the core urostylids.
Highlights
The possession of three clearly differentiated frontal cirri and a midventral complex composed of midventral pairs only places Wilbertophrya n. g. unequivocally in the family Holostichidae
Based on the following combination of features, that is, single left and right marginal rows, a continuous adoral zone, presence of frontoterminal cirri, clearly differentiated frontal cirri, and midventral cirral pairs arranged in a zigzag pattern, five genera in the family Holostichidae should be compared with Wilbertophrya n. g., namely, Anteholosticha Berger, 2003; Arcuseries Huang et al, 2014; Afrothrix Foissner, 1999; Acuholosticha Li et al, 2017; and Holosticha Wrzesniowski, 1877 (Berger, 2003; Huang et al, 2014; Li et al, 2017)
All five of these genera differ from Wilbertophrya n. g. in having a buccal cirrus and pretransverse cirri, whereas both these structures are lacking in the new genus (Berger, 2006; Huang et al, 2014; Li et al, 2017)
Summary
Hypotrich ciliates are a large, ubiquitous group that play key roles in many ecosystem processes and as model organisms in a wide range of biological studies (Berger, 1999, 2011; Song and Shao, 2017; Chen et al, 2019, 2020; Kim and Min, 2019; Kim et al, 2019; Li et al, 2019; Wang et al, 2019; Gao et al, 2020; Sheng et al, 2020). Urostylids are one of the most speciose and best-known groups within the subclass Hypotrichia Stein, 1859. Their evolutionary relationships and genus- or family-level definitions remain problematic as recognized in several recent reports (Berger, 2006; Lu et al, 2018, 2020; Luo et al, 2018, 2019; Jung and Berger, 2019; Wang et al, 2021a; Zhang et al, 2020). Sp., isolated from a wetland in the Qinling Mountains area near Xi’an Both species were characterized based on morphological observations of specimens in vivo and following silver staining. Their molecular phylogeny was analyzed based on small subunit ribosomal DNA (SSU rDNA) sequence data
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