Morphology of four new solitary sessile peritrich ciliates from the Yellow Sea, China, with description of an unidentified species of Paravorticella (Ciliophora, Peritrichia)

On four epibiotic peritrichous ciliates (Protozoa, Ciliophora) found in Lake Weishan Wetland: morphological and molecular data support the establishment of a new genus, Parapiosoma gen. nov., and two new species

During a study on the diversity of ciliated protists in Lake Weishan Wetland, the largest wetland in northern China, four epibiotic sessilid peritrichs were isolated from aquatic host animals. Two of them, i.e., Epistylis cambari Kellicott, 1885 and Epistylis lwoffi Fauré-Fremiet, 1943, were known species whereas the other two, i.e., Parapiosoma typicum gen. nov., sp. nov. and Orborhabdostyla gracilis sp. nov., are new to science. The new genus Parapiosoma gen. nov. is characterized by its branched non-contractile stalk, everted peristomial lip, obconical macronucleus and transverse silverlines. Two species are assigned to the new genus, namely Parapiosoma typicum sp. nov. and Parapiosoma gasterostei (Fauré-Fremiet, 1905) comb. nov. Morphologically, P. typicum sp. nov. is recognized by its goblet-shaped zooids, single-layered peristomial lip, dichotomously branched stalk, and infundibular polykinety 3 (P3) containing three equal-length rows. Orborhabdostyla gracilis sp. nov. is characterized by its slender zooid, curved macronucleus, and three equal-length rows in infundibular P3. Improved diagnoses and redescriptions of E. cambari and E. lwoffi are provided including, for the first time, data on the ciliature of E. cambari. Phylogenetic analyses based on SSU rDNA, ITS1-5.8S rDNA -ITS2, and LSU rDNA sequence data strongly support the assertion that the family Epistylididae comprises morphospecies with different evolutionary lineages and indicate that Parapiosoma gen. nov. may represent a new taxon at family level.

Integrative Studies on Three Epibiotic Epistylis Species (Protozoa, Ciliophora, Peritrichia) in Lake Weishan Wetland, Northern China, Including the Establishment of a New Species

Three epibiotic Epistylis species, i.e., Epistylis weishanensis sp. nov., Epistylis daphniae Fauré-Fremiet, 1905, and Epistylis pygmaeum (Ehrenberg, 1838) Foissner et al., 1999, were investigated based on their living morphology, infraciliature, and small subunit (SSU) rDNA sequence data. Epistylis weishanensis sp. nov. is characterized by its double-layered peristomial lip, contractile vacuole located on the dorsal wall of the infundibulum, infundibular polykinety 3 (P3) composed of three equal-length rows that terminate above infundibular polykinety 1 (P1), 50-62 silverlines between the peristome and the trochal band, and about 30 silverlines between the trochal band and the scopula. Based on previous and newly obtained data for E. daphniae and E. pygmaeum, improved diagnoses and redescriptions are provided including, for the first time, data on their infraciliature. Phylogenetic analyses reveal that all three species do not group within the major clade of Epistylis, supporting the assertion that the genus Epistylis should be an assemblage of morphospecies and therefore needs to be revised.

Incorporating mitogenome sequencing into integrative taxonomy: The multidisciplinary redescription of the ciliate Thuricola similis (Peritrichia, Vaginicolidae) provides new insights into the evolutionary relationships among Oligohymenophorea subclasses

The evolutionary relationships among Oligohymenophorea subclasses are under debate as the phylogenomic analysis using a large dataset of nuclear coding genes is significantly different to the 18S rDNA phylogeny, and it is unfortunately not stable within and across different published studies. In addition to nuclear genes, the faster-evolving mitochondrial genes have also shown the ability to solve phylogenetic problems in many ciliated taxa. However, due to the paucity of mitochondrial data, the corresponding work is scarce, let alone the phylogenomic analysis based on mitochondrial gene dataset. In this work, we presented the characterization on Thuricola similis Bock, 1963, a loricate peritrich (Oligohymenophorea), incorporating mitogenome sequencing into integrative taxonomy. As the first mitogenome for the subclass Peritrichia, it is linear, 38,802 bp long, and contains two rRNAs, 12 tRNAs, and 43 open reading frames (ORFs). As a peculiarity, it includes a central repeated region composed of tandemly repeated A-T rich units working as a bi-transcriptional start. Moreover, taking this opportunity, the phylogenomic analyses based on a set of mitochondrial genes were also performed, revealing that T. similis, as a representative of Peritrichia subclass, branches basally to other three Oligohymenophorea subclasses, namely Hymenostomatia, Peniculia, and Scuticociliatia. Evolutionary relationships among those Oligohymenophorea subclasses were discussed, also in the light of recent phylogenomic reconstructions based on a set of nuclear genes. Besides, as a little-known species, T. similis was also redescribed and neotypified based on data from two populations collected from wastewater treatment plants (WWTPs) in Brazil and Italy, by means of integrative methods (i.e., living observation, silver staining methods, scanning and transmission electron microscopy, and 18S rDNA phylogeny). After emended diagnosis, it is characterized by: (1) the sewage habitat; (2) the lorica with a single valve and small undulations; (3) the 7-22 µm-long inner stalk; and (4) the presence of only a single postciliary microtubule on the left side of the aciliferous row in the haplokinety. Among Vaginicolidae family, our 18S rRNA gene-based phylogenetic analysis revealed that Thuricola and Cothurnia are monophyletic genera, and Vaginicola could be a polyphyletic genus.

Morphology and molecular analyses of four epibiotic peritrichs on crustacean and polychaete hosts, including descriptions of two new species (Ciliophora, Peritrichia)

Four epibiotic sessilid peritrichs, i.e., Zoothamnium wilberti n. sp., Baikalonis microdiscus n. sp., Epistylis anastatica (Linnaeus, 1767) Ehrenberg, 1830, and Rhabdostyla commensalisMöbius, 1888, were isolated from one syllid polychaete and three crustacean hosts in Qingdao, China. For each species, specimens were observed both in vivo and following silver staining. Their SSU rDNA was also sequenced for phylogenetic analyses. Zoothamnium wilberti n. sp. is characterized by the appearance of its colony, which is up to 350 μm high, and usually has fewer than 16 zooids, and the dichotomously branched stalk with transverse wrinkles, the conspicuously conical peristomial disc, and infundibular polykinety 3 comprising three isometric ciliary rows. Baikalonis microdiscus n. sp. can be recognized by its barrel-shaped zooid, small peristomial disc, smooth and short stalk, and its unusual infundibular polykinety 3 comprising a long inner row and a short outer row. Two poorly known species, i.e., Epistylis anastatica and Rhabdostyla commensalis, are redescribed and redefined. Phylogenetic analyses reveal that: (i) R. commensalis is closely related to the family Astylozoidae rather than to the morphologically similar Epistylididae; (ii) B. microdiscus n. sp. is sister to the family Scyphidiidae; (iii) E. anastatica groups with vorticellids and ophrydiids, which further supports the polyphyly of the genus Epistylis; and (iv) Z. wilberti n. sp. is nested within the Zoothamniidae, as expected.

Morphology and Phylogeny of Three Pseudovorticella Species (Ciliophora: Peritrichia) from Brackish Waters of China

The biodiversity of peritrich ciliates from brackish biotopes is rarely investigated, especially members of the genus Pseudovorticella. Here, the morphology of three species of Pseudovorticella, i.e. P. cf. vestita (Stokes, 1883) Jankowski, 1976, P. spathulata sp. n., and P. qinghaiensis sp. n. isolated from brackish waters were studied. Pseudovorticella cf. vestita is characterized by inverted bell-shaped cell; a J-shaped macronucleus; a single contractile vacuole ventrally located; P3 three-rowed; pellicle striated with highly developed pellicular vesicles; 18-22 transverse silverlines between peristome and aboral trochal band, and 9-13 between aboral trochal band and scopula. Pseudovorticella spathulata sp. n. differs from its congeners by the following combination of characters: elongate-elliptical cell; a single contractile vacuole near ventral wall of infundibulum; a J-shaped macronucleus; P3 three-rowed; 24-34 silverlines between oral area and aboral trochal band and 6-10 between aboral trochal band and scopula. Pseudovorticella qinghaiensis sp. n. is characterized by: cell with an oval outline; a single contractile vacuole near ventral wall of infundibulum; a C-shaped macronucleus; P3 three-rowed; 30-35 and 9-11 transverse silverlines above and below the trochal band, respectively. The SSU rDNA sequences of five Pseudovorticella species, namely P. annulata, P. monilata, P. parakenti, P. spathulata sp. n., and P. cf. vestita, plus that of Zoothamnium hartwigi, are reported for the first time and their evolutionary relationships are investigated. Five undefined Pseudovorticella forms are considered might be conspecific with P. monilata. Two congeners are conspecific with P. spathulata sp. n. Phylogenetic analyses based on SSU rDNA sequences reveal that Pseudovorticella is not monophyletic and Z. hartwigi clusters with its congeners as expected.

Novel contributions to the peritrich family Vaginicolidae (Protista: Ciliophora), with morphological and phylogenetic analyses of poorly known species of Pyxicola, Cothurnia and Vaginicola

The classification of loricate peritrich ciliates is difficult because of an accumulation of several taxonomic problems. In the present work, three poorly described vaginicolids, Pyxicola pusilla, Cothurnia ceramicola and Vaginicola tincta, were isolated from the surface of two freshwater/marine algae in China. In our study, the ciliature of Pyxicola and Vaginicola is revealed for the first time, demonstrating the taxonomic value of infundibular polykineties. The small subunit rDNA, ITS1-5.8S rDNA-ITS2 region and large subunit rDNA of the above species were sequenced for the first time. Phylogenetic analyses based on these genes indicated that Pyxicola and Cothurnia are closely related. The present study suggested that the loricate species probably represent a distinct lineage in peritrich evolution and both genera Cothurnia and Thuricola are monophyletic. Pyxicola pusilla, Cothurnia ceramicola and Vaginicola tincta are recircumscribed.