Sampling hidden microbial eukaryotic biodiversity in the tropics: new insights from the Paramecium aurelia complex (Ciliophora, Protozoa)

Ciliates, including the genus Paramecium, are among the most thoroughly researched groups of free-living microbial eukaryotes. However, our knowledge of their biodiversity appears to be restricted. Therefore, more data is required for tropical regions, to generate a more accurate picture of the distribution of the cryptic Paramecium species. In the current paper, recent data on the tropical biodiversity of the Paramecium aurelia species complex is presented. We believe that the COI mtDNA fragment allows for an evaluation of the geographic variation of particular cryptic species within the Paramecium aurelia complex, while also being sufficient for species identification. The obtained data indicates that the examined tropical populations may be very variable (with more than 50% previously unknown COI haplotypes discovered). Consequently, it is reasonable to assume that tropical environments reveal a high biodiversity of Paramecium ciliates.