Morphogenesis and Molecular Characterization of a Little Known Soil Ciliate, Oxytricha nauplia Berger et Foissner, 1987 (Ciliophora, Sporadotrichida)

Background: The taxonomy of tintinnine ciliates is vastly unresolved because it has traditionally been based on the lorica (a secreted shell) and it has only recently incorporated cytological and molecular information. Tintinnopsis, the most speciose tintinnine genus, is also the most problematic: it is known to be non-monophyletic, but it cannot be revised until more of its species are studied with modern methods.Results: Here, T. hemispiralis Yin, 1956, T. kiaochowensis Yin, 1956, and T. uruguayensis Balech, 1948, from coastal waters of China, were studied. Lorica and cell features were morphometrically investigated in living and protargol-stained specimens, and sequences of three ribosomal RNA (rRNA) loci were phylogenetically analyzed. The three species show a complex ciliary pattern (with ventral, dorsal, and posterior kineties and right, left, and lateral ciliary fields), but differ in lorica morphology, details of the somatic ciliature and rRNA gene sequences. Tintinnopsis hemispiralis is further distinguished by a ciliary tuft (a ribbon of very long cilia originated from the middle portion of the ventral kinety and extending out of the lorica) and multiple macronuclear nodules. Both T. kiaochowensis and T. uruguayensis have two macronuclear nodules, but differ in the number of somatic kineties and the position of the posterior kinety. Two neotypes are fixed for T. hemispiralis and T. kiaochowensis to stabilize the species names objectively, mainly because of the previous unavailability of type materials. By phylogenetic analysis and comparison with closely-related species, we infer that the ciliary tuft and details such as the commencement of the rightmost kinety in the lateral ciliary field are synapomorphies that may help clarify the systematics of Tintinnopsis-like taxa.Conclusion: The redescriptions of three poorly known Tintinnopsis species, namely T. hemispiralis, T. kiaochowensis, and T. uruguayensis firstly revealed their ciliary patterns and rRNA sequences. This study expands knowledge and database of tintinnines and helps in identifying potential synapomorphies for future taxonomic rearrangements.

As a dominant group of microzooplankton, the tintinnid ciliates (Ciliophora: Tintinnida) play a crucial role in aquatic ecosystems by linking the microbial food loop with the classical planktonic food web. However, taxonomic understanding has been greatly hindered by lorica polymorphism, combined with limited data on living cells and infraciliature, which in turn constrains progress in related fields such as ecology and physiology. In the present study, two freshwater tintinnids, namely Tintinnopsis wangi Nie, 1933, and T. tubuformis Chiang, 1956, collected from the Weishan Lake Basin, China, were redescribed based on living observation and protargol staining. Furthermore, the ciliary pattern of T. wangi is first reported, while that of another species corresponds well with its Shanghai population, indicating relatively high intraspecific stability of ciliary patterns in Tintinnida. In addition, based on the comparison of morphological characteristics, T. anhuiensis Nie, 1933, and T. sinensis Chiang, 1956, are considered synonyms of T. wangi. The characteristics of all species were compared with their original descriptions and further studies.

Rapid climate change and human disturbance have caused serious damage and shrinkage of the wetlands in the Mongolian Plateau, posing severe challenges to environmental development. Based on remote sensing images and DEM data, this study established a series of datasets for lakeside wetlands in the Mongolian Plateau in 2000, 2010 and 2020, and investigated the dynamic evolution of lakeside wetlands in the Mongolian Plateau through spatial and temporal analyses. The results showed that in 2000, there were 564 lakes (>1 km2) in the Mongolian Plateau, with a total area of about 55216.47 km2. Compared with 2000, the area of lakes in 2010 was significantly reduced, and there was a significant increase in the number of woody marshes and a reduction in the number of herbaceous marshes. In 2020, the lakes in the central part of the Mongolian Plateau were smaller than in 2010. The areas of lakes in the western, southern and eastern regions were increasing, and the areas of herbaceous swamps, woody marshes and meadows were increasing overall. Lakes, bare land and saline-alkali land decreased overall. The degree of salinization was reduced over the study period. There was a significant correlation between the Adaptive Palmer Drought Index (scPDSI) and lake area. In the past two decades, the climatic factors and human activities of the Mongolian Plateau have profoundly affected the evolution of the lakeside wetlands. We should prioritize the protection of lakes and wetland resources in order to achieve the dynamic balance of wetland ecology.

Wetlands are important for maintaining global ecosystem functions, mitigating global climate change, and regulating regional climate change. Ecological problems caused by global climate change have had serious impacts on plant distribution patterns in the wetlands of riparian zones, as well as on microbial community habitats in the soil. This study was based on a field sampling survey of the distribution characteristics of plant communities in the Ulson River, combined with remote sensing to obtain the spatial distribution pattern of vegetation in the riparian wetland. High-throughput sequencing technology combined with the characteristics of soil physicochemical factors were then used to explore the distribution characteristics of the community structures of soil bacteria and fungi under different vegetation types in the Ulson River Basin, in order to reveal the pattern of changes of soil microbial microorganisms under the different vegetation types in the wetlands of the riparian area and the factors driving those changes. The results showed an obvious banding phenomenon of wetland vegetation in the Ulson River Basin. Proteobacteria ranked first in relative abundance in all the sample plots and were the dominant bacteria in the study area. Ascomycota and Basidiomycota were the dominant fungi in the study area. In swamp areas, degenerate swamp soils, soil moisture content, and soil bulk density affected the microbial richness directly or indirectly by controlling soil nutrients. Plant aboveground biomass was the most significant factor influencing microbial diversity in a typical wet meadow sample. In salinized meadows and swamped meadows, electrical conductivity affected microbial richness and soil bulk density was the main factor influencing microbial diversity. The findings of this study can provide a theoretical basis for the ecological restoration of degraded riparian wetlands and further clarification of soil ecosystem functions in riparian wetlands.