New Paramecium (Ciliophora, Oligohymenophorea) congeners shape our view on its biodiversity

Abstract

Paramecium is one of the best known and most intensely studied ciliate genera. It currently comprises 18 morphospecies including the P. aurelia complex of 15 sibling species. Here, we describe the new morphospecies Paramecium buetschlii sp. nov. from a freshwater pool in Norway, featuring unusual combinations of morphological characters and a high genetic diversity relative to other congeners. Three further investigated Paramecium spp. from Germany, Hungary, and Brazil are treated as cryptic species, because they are difficult to discriminate from other members of the genus relying on morphological criteria only. However, DNA-based taxonomic markers (18S-rDNA and mitochondrial COI) clearly indicate they are separate species. Due to the lack of an appropriate systematic term within the International Code of Zoological Nomenclature for distinguishing cryptic from valid biological species, we propose the provisional status Eucandidatus as a component of the taxonomic name when describing new but cryptic eukaryotes. Based on our data, we postulate that even within Europe there is a higher biodiversity within this common ciliate group that is heavily used in the classroom. By uncovering potentially distinct species that have been classified under the same species names, our molecular analyses further suggest a higher current stock diversity in Paramecium than previously thought. We also would like to emphasize that under-sampling is another major issue in estimating protist diversity. Future large-scale studies based on extensive sampling not only in exotic and remote regions, but also in less frequently sampled areas, will therefore likely improve our understanding of species richness and diversity

Rare Freshwater Ciliate Paramecium chlorelligerum Kahl, 1935 and Its Macronuclear Symbiotic Bacterium “Candidatus Holospora parva”

“…These “Russian” P . chlorelligerum sequences were 99.8% identical to representatives of the “German” population [1, 12]. In those sequences, respectively three (position 1029, 1298 and 1310) and two (positions 1298 and 1310) mismatches were present.…”

“…In those sequences, respectively three (position 1029, 1298 and 1310) and two (positions 1298 and 1310) mismatches were present. The two 18S rDNA sequences produced from German population [1, 12] were differing in a nucleotide, a W in [12]. To resolve this ambiguity, we resequenced a sample derived from the German population obtaining the same result as [1].…”

“…One of the most studied ciliate genus is Paramecium (Ciliophora, Oligohymenophorea), which comprises nineteen valid morphospecies [1]. Some of these species seem to be cosmopolitan, while other Paramecium species are less widely distributed or might be even considered endemic [2, 3].…”

“…Some of these species seem to be cosmopolitan, while other Paramecium species are less widely distributed or might be even considered endemic [2, 3]. After the initial work of Müller in 1786 [4], more than forty species descriptions of the Paramecium genus have been published [1, 2, 5–6]. Some of these species have been retrieved only once and have not been found anymore after description.…”

Worldwide sampling reveals low genetic variability in populations of the freshwater ciliate Paramecium biaurelia (P. aurelia species complex, Ciliophora, Protozoa)

“…In the genus Paramecium, strain crosses and molecular analyses have revealed the occurrence of cryptic differentiation (for example Sonneborn 1975;Greczek-Stachura et al 2012;Tarcz et al 2014; in the majority of the 19 valid morphospecies (Fokin 2010(Fokin /2011Krenek et al 2015). One of these is Paramecium aurelia, which is in fact a complex of 15 sibling species (Sonneborn 1975;Aufderheide et al 1983) that are morphologically indistinguishable but sexually isolated.…”