Abstract
Background: Hypotrichia are a group with the most complex morphology and morphogenesis within the ciliated protists. The classification of the genus Holostichides is poorly understood particularly due to the lack of molecular data. Hence, the systematic relationship between this genus and other taxa in the subclass Hypotrichia remains unresolved. In this paper, the morphology and morphogenesis of Holostichides songi nov. spec. were studied, in addition, genomic DNA was extracted in order to sequence the small subunit rDNA. The main aims of this study were to document morphogenesis in H. songi nov. spec. and investigate the systematics of Holostichides based on morphology, morphogenetic, and molecular data.Results: A new bakuellid ciliate, Holostichides songi nov. spec. isolated from China, is investigated in terms of its morphology, ontogenesis, and molecular phylogenesis. It is characterized by size in vivo 150–180 µm × 45–60 µm; 27–46 macronuclear nodules; cortical granules dark, spherical, about 0.5 µm across, clustered in groups and then arranged longitudinally; three frontal cirri with one to four smaller cirri below the middle one, one buccal cirrus, 9–15 frontoterminal cirri, and midventral complex composed of five to eight cirral pairs and two long midventral rows. The main events during binary fission are as follows: (1) in the proter, the undulating membrane anlage is formed from both the dedifferentiation of old undulating membranes and the basal bodies developing de novo, and the posterior part of the parental adoral zone of membranelles is renewed by new structure formed from the oral primordium; (2) in the opisthe, the oral primordium is formed intrakinetally; (3) Besides the second frontal cirrus and buccal cirrus, the frontoventral-transverse cirral anlage II produces the extra one to four cirri. Phylogenetic analyses based on SSU rDNA sequence data suggest a close relationship between Holostichides songi nov. spec. and its congeners, indicating that the genus Holostichides is monophyletic.Conclusions: The new bakuellid ciliate, Holostichides songi nov. spec. was studied using standard methods. In addition, the monophyly of the genus Holostichides is well supported in the phylogenetic tree.
The insights into the systematic relationship of Gastrostyla-affinitive genera, with report on a new saline soil ciliate genus and new species (Protozoa, Ciliophora)