Further insights into the phylogeny of facultative parasitic ciliates associated with tetrahymenosis (Ciliophora, Oligohymenophorea) based on multigene data

Abstract

Tetrahymenosis, caused by about 10 Tetrahymena species, is an emerging problem inflicting a significant economic loss on the aquaculture industry worldwide. However, in the order Tetrahymenida, there are many unresolved evolutionary relationships among taxa. Here we report 21 new sequences, including SSU‐rRNA, ITS1‐5.8S‐ITS2 rRNA and LSU‐rRNA, genes of 10 facultative parasitic Tetrahymena associated with tetrahymenosis, and conduct phylogenetic analyses based on each individual gene and a three‐gene concatenated dataset. The main findings are: (1) All the parasitic and facultative parasitic species cluster in borealis group. (2) With the addition of new sequences, Tetrahymena is still divided into three groups, namely the “borealis group”, the “australis group,” and the “paravorax group.” (3) the cluster pattern of all the newly sequenced facultative parasitic Tetrahymena species shows that members of the “borealis” group may be more susceptible to parasitism. (4) phylogeny based on concatenated genes show that T. pyriformis, T. setosa, and T. leucophrys have close relationship.

Internal Transcribed Spacers as Phylogenetic Markers Enable Species-level Metataxonomic Analysis of Ciliated Protozoa

“…Being intrinsically more divergent than the flanking rRNA genes, ITS1 and ITS2 have been widely used in mycobiome (fungal microbiome) analysis for species identification and profiling [29,30], offering significantly enhanced taxonomic resolution. These two ITS regions have been used in studies of free-living ciliates to infer their evolution and refine their phylogeny among closely related ciliate species [31,32]. They have also facilitated the discovery of new ciliate species and genera [33][34][35].…”