Morphological And Systematic Studies Of 16 Freshwater Ciliates In Class Oligohymenophorea

The ciliates in class Oligohymenophorea exhibit great species richness and biological diversity.The forms assigned to this group are generally small and widely distributing in various habitats such as seawater,freshwater,and soil.Cliates in Oligohymenophorea play important roles in water environment ecology,aquaculture diseases and sewage treatment.Investigations on marine ciliates of Oligohymenophorea have been carried out for many years,whereas for freshwater species is still lacking.Harbin region of the Songhua River Basin was selected as the main samples-collecting sites,and modern taxonomic techniques such as in vivo observation,silver staining and electron microscopy,as well as molecular biological methods are used in the present work,to reveal the detailed morphology and systematic relationships of 16 freshwater oligohymenophorea ciliates.This work include morphological and systematic parts.The former was carried out by providing detailed and accurate morphological information,correcting taxonomic errors in species identifation and supplementing key taxonomic information of known species such as infraciliature;the latter was composed of SSU rDNA gene sequencing,sequence alignment and phylogenetic analysis based on morphology and molecular information.The details as following:1.Established several new taxa and new populations of known species are described in detail.A new genus: Apouronema Pan et al.,2019 and four new species: Apouronema harbinensis Pan et al.,2019;Cyclidium vorax Pan et al.,2019;Cyclidium orientalis Pan et al.,2019;Dexiotricha orientalis n.sp.were found and defined.A detailed re–description of known but long–term ambiguous categories and new definitions were provided: Lembadion gabonensis Dragesco,1965;Tetrahynema setosa(Schewiakoff 1892)McCoy(1975),T.vorax(Kidder,Lilly & Claff,1940)Kidder,1941 and T.chironomi Corliss,1960.Based on the new characteristics of the new population,complementary definitions of the known species are supplied.2.Morphological and structural characteristics of different oligohymenophorea ciliates are studied,as well as compare and summarize the morphological and structural features of different morphological structure,focus on the phylogenetic relationships between genus and populations,and clean up the confusion and error of the remaining species classification and taxonomy in class oligohymenophorea.3.The small subunit ribosomal rRNA gene(SSU rDNA)sequences of Apouronema harbinensis,Uronema marinum,Cyclidium vorax,Cyclidium orientalis,Dexiotricha orientalis,Paramecium caudatum,Lembadion gabonensis;Tetrahynema setosa;Tetrahynema vorax;Tetrahymena chironomi,and the cox1 gene sequence of Tetrahynema setosa are provided.The sequences above were submitted to GenBank database.4.Based on the information from sequences data of SSU rRNA,sequences analyses and construction of the phylogenetic trees were carried out,in order to further analyze the internals relationships within Scuticociliatia,Peniculia and Hymenostomatia.Therefore,modern research techniques and methods were used to clean up and supplement the taxonomy of freshwater species in the class Oligohymenophora to a certain extent,some new orders were established,and the existing confusion / errors were cleared / corrected;The sequences of the small subunit ribosomal rRNA genes and mitochondrial genes(partial species)were supplemented,and the systematic status and kinship of important species are explored.So as to provide a reference for related research.