Zhishuai Qu

The morphology and phylogeny of two poorly known species, Uronema nigricans (Müller, 1786) Florentin, 1901 and Lembadion lucens (Maskell, 1887) Kahl, 1931, were respectively collected from a eutrophic freshwater river in Shenzhen and an oligotrophic lake in Zhanjiang (both in southern China) and investigated using standard taxonomic methods. The sampled population of Uronema nigricanswas characterized by a cell size of 30–40 μm × 12–20 μm in vivo, an elongated elliptical outline with a prominent apical plate, and 13–15 somatic kineties. The sampled population of Lembadion lucenswas characterized by a cell size of 45–80 μm × 20–50 μm in vivo, 25–35 somatic kineties, five or six caudal kinetosomes with cilia about 20 μm in length, and a single right-positioned contractile vacuole.The small subunit ribosomal RNA gene (SSU rDNA) of these species was sequenced and compared with those of their congeners to reveal nucleotide differences. The phylogenetic trees showed that the Shenzhen population of Uronema nigricans clusters with two other sequences under the name of “Uronema nigricans” (which are possibly misidentified) and then groups with Uronemita sinensis (Pan et al., 2013) Liu et al., 2016 with full support. Phylogenetic analyses indicated that genus Lembadion is monophyletic with full support provided by both Bayesian inference and maximum likelihood algorithms. Based on analyses of morphological and sequence data, Uronemita sinensis may represent a new genus between Uronema and Uronemita.

We isolated an encysted ciliate from a geothermal field in Iceland. The morphological features of this isolate fit the descriptions of Dexiotricha colpidiopsis (Kahl, 1926) Jankowski, 1964 very well. These comprise body shape and size in vivo, the number of somatic kineties, and the positions of macronucleus and contractile vacuole. Using state-of-the-art taxonomic methods, the species is redescribed, including phylogenetic analyses of the small subunit ribosomal RNA (SSU rRNA) gene as molecular marker. In the phylogenetic analyses, D. colpidiopsis clusters with the three available SSU rRNA gene sequences of congeners, suggesting a monophyly of the genus Dexiotricha. Its closest relative in phylogenetic analyses is D. elliptica, which also shows a high morphological similarity. This is the first record of a Dexiotricha species from a hot spring, indicating a wide temperature tolerance of this species at least in the encysted state. The new findings on D. colpidiopsis are included in a briefly revision of the scuticociliate genus Dexiotricha and an identification key to the species.