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Tetrahymena australis (Protozoa, Ciliophora): A Well‐Known But “Non‐Existing” Taxon – Consideration of Its Identification, Definition and Systematic Position
Author(s) -
Liu Mingjian,
Fan Xinpeng,
Gao Feng,
Gao Shan,
Yu Yuhe,
Warren Alan,
Huang Jie
Publication year - 2016
Publication title -
journal of eukaryotic microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.067
H-Index - 77
eISSN - 1550-7408
pISSN - 1066-5234
DOI - 10.1111/jeu.12323
Subject(s) - biology , ribosomal rna , tetrahymena pyriformis , tetrahymena , population , phylogenetic tree , phylogenetics , subspecies , species complex , protozoa , zoology , evolutionary biology , gene , genetics , demography , sociology
A cryptic species of the Tetrahymena pyriformis complex, Tetrahymena australis , has been known for a long time but never properly diagnosed based on taxonomic methods. The species name is thus invalid according to the International Code of Zoological Nomenclature. Recently, a population isolated from a freshwater lake in Wuhan, China was investigated using live observations, silver staining methods and gene sequence data. This organism can be separated from other described species of the T. pyriformis complex by its relatively small body size, the number of somatic kineties and differences in sequences of two genes, namely the small subunit ribosomal RNA ( SSU rRNA ) and the mitochondrial cytochrome c oxidase subunit I ( cox1 ). We compared the SSU rRNA gene sequences of all available Tetrahymena species to reveal the nucleotide differences within this genus. The sequence of the Wuhan population is identical to two sequences of a previously isolated strain of T. australis ( ATCC #30831). Phylogenetic analyses indicate that these three sequences (X56167, M98015, KT 334373) cluster with Tetrahymena shanghaiensis ( EF 070256) in a polytomy. However, sequence divergence of the cox1 gene between the Wuhan population and another strain of T. australis ( ATCC #30271) is 1.4%, suggesting that these may represent different subspecies.