An Integrative Investigation of Parabistichella variabilis (Protista, Ciliophora, Hypotrichia) Including Its General Morphology, Ultrastructure, Ontogenesis, and Molecular Phylogeny

Abstract

Hypotrichs are a highly differentiated and very diverse group of ciliated protists. Their systematics and taxonomy are challenging and call for detailed investigations on their general morphology, ultrastructure, ontogenesis, and molecular phylogeny. Here, a comprehensive study is conducted on a brackish water population of Parabistichella variabilis using light and electron microscopy and phylogenetic analyses based on small subunit ribosomal DNA sequence data. Its morphology, including the infraciliature, pellicle, nuclei, buccal seal, and extrusomes, is documented. The present findings indicate that in P. variabilis: (i) the cortical granules are extrusomes, which differ from those of other hypotrichs; (ii) the buccal seal is bounded by the plasma membrane and contains a single layer of longitudinal microtubules; (iii) two contractile vacuoles might be present rather than one; and (iv) the pharyngeal disks are bounded by a single membrane. Early‐to‐middle stages of ontogenesis are described for the first time, enabling the complete characterization of this process. Phylogenetic analyses indicate that Parabistichella variabilis is closely related to several species from different genera, such as Orthoamphisiella breviseries, Uroleptoides magnigranulosus, and Tachysoma pellionellum. However, ultrastructural and gene sequence data for more taxa are needed in order to resolve the systematics of Parabistichella.

Morphology, Morphogenesis and Phylogenetic Position of the Soil Hypotrichous Ciliate, Parabistichelladieckmanni (Foissner, 1998) Foissner, 2016 (Ciliophora, Hypotrichia), with Notes on the Phylogeny of Parabistichella

“…cheni was found and more morphogenetic information was provided, some morphogenetic features are still unknown (including the formation of the frontoventral row) (Dong et al. 2020). According to current knowledge, the main difference between P .…”

Morphology, morphogenesis and phylogeny of the new soil ciliate, Bistichella granulifera n. sp. (Protista, Ciliophora)

“…Hitherto, in Parabistichella, morphogenetic data is available for only three species, which are P. variabilis, P. cystiformans and P. dieckmanni. However, each frontoventral row is produced by one anlage in P. cystiformans, whereas the left frontoventral row originating from two anlagen in P. dieckmanni (morphogenesis is described very roughly in the type species, P. variabilis, so data unavailable) [10,19,21,22]. B. granulifera n. sp.…”

“…Hypotrichous ciliates are a highly differentiated group within ciliated protists, and have diversi ed morphological features and complicated morphogenetic processes [1][2][3][4][5][6][7][8]. To date, many studies have been carried out on the classi cation and phylogeny of hypotrichs [9][10][11][12][13][14].…”

Ultrastructural Features of an Abundant and Ubiquitous Marine Ciliate, Uronychia binucleata (Protista, Ciliophora, Euplotida)

“…The SEM method was mainly used according to Gu and Ni (1993) and Dong et al (2020a). The specimens with approximately 1.5 ml of culture medium were transferred into a 1:6 mixture of 1% OsO 4 (diluted from 4% OsO 4 by 30 salinity filtering artificial marine water) and saturated solution of HgCl 2 for 10 min at room temperature (25 • C).…”

“…In the present study, four membrane structures are inside and outside the right and left components of the undulating membrane, respectively, which suggests that the undulating membrane is bounded by a cortical flap. It is worth noting that one or two layer(s) of rootless membrane structures are sometimes present beneath the right component of the undulating membrane, which might be caused by two circumstances: (1) the cortical flap curves and cuts twice; or (2) it is the buccal seal (Foissner and Al-Rasheid, 2006;Berger, 2008;Dong et al, 2020a).…”