Ewa Przyboś

Genetic Diversity in the Paramecium aurelia Species Complex

Current understanding of the population genetics of free-living unicellular eukaryotes is limited, and the amount of genetic variability in these organisms is still a matter of debate. We characterized-reproductively and genetically-worldwide samples of multiple Paramecium species belonging to a cryptic species complex, Paramecium aurelia, whose species have been shown to be reproductively isolated. We found that levels of genetic diversity both in the nucleus and in the mitochondrion are substantial within groups of reproductively compatible P. aurelia strains but drop considerably when strains are partitioned according to their phylogenetic groupings. Our study reveals the existence of discrepancies between the mating behavior of a number of P. aurelia strains and their multilocus genetic profile, a controversial finding that has major consequences for both the current methods of species assignment and the species problem in the P. aurelia complex.

Cytochrome b sequence data suggest rapid speciation within the Paramecium aurelia species complex

We investigated mitochondrial Cytochrome b sequences from all 15 members of the enigmatic Paramecium aurelia species complex (Ciliophora). The analysis revealed high genetic distances between the different P. aurelia species (6.1-19.8%) and a largely unresolved, star-like phylogenetic tree. This result strongly supports a rapid radiation in the evolutionary history of this species complex and it correlates well with the hypothesis that the extant species diversity may have originated from the neutral consequences of a whole genome duplication in the common ancestor of P. aurelia.

Application of a Multiplex PCR with Specific PCR Primers for the Detection of the Genus Paramecium and the Paramecium aurelia Complex

The representatives of the genus Paramecium are well-studied ciliates and can be used in water quality assessment and the determinations of saprobic levels. For these applications, a clear and unambiguous identification of ciliate assemblages is essential, which is typically based on morphological characters requiring a sound taxonomic knowledge and experience in species determination including microscopic identification of both living and stained specimens. Therefore, we developed and applied specific PCR primers for the detection of species belonging to the genus Paramecium and the Paramecium aurelia complex. These primers were successfully tested with different Paramecium species including representatives of the P. aurelia complex as well as closely related species like Frontonia sp. and Tetrahymena sp. in both experimental and environmental samples. These primers can be used in a simultaneous approach achieving fast and reliable results with regard to determination of ciliate community and water assessment.

New European stands of Paramecium pentaurelia, Paramecium septaurelia, and Paramecium dodecaurelia, genetic and molecular studies

New stands of rare species of the Paramecium aurelia complex were found in Europe, i.e. P. pentaurelia and P. dodecaurelia in Italy and P. septaurelia in Germany. The species were identified by mating reactions with the standard strains of each species. Their relationships with some other known strains of particular species were studied by classical strain crosses (survival in F1 and F2 generations) and by comparison of RAPD-PCR fingerprints. The presence of the cosmopolitan species P. tetraurelia in Italy was also recorded.

Recent data on the occurrence of species of the Paramecium aurelia complex in Europe

Among 15 species of the Paramecium aurelia complex known world-wide, 10 have been found in Europe, namely: P. primaurelia, P. biaurelia, P. triaurelia, P. tetraurelia, P. pentaurelia, P. sexaurelia, P. septaurelia, P. novaurelia, P. dodecaurelia, and P. tredecaurelia. Recent data on the frequency of occurrence of the species in Europe are given in the paper.

Relationships of species of the Paramecium aurelia complex (Protozoa, Ph. Ciliophora, Cl. Oligohymenophorea) based on sequences of the histone H4 gene fragment.

A fragment ofhistone H4 gene (160 bp long) was sequenced in the standard strains of P. primaurelia (DQ067620), P. biaurelia (DQ067621), P. tetraurelia (DQ067622), P. pentaurelia (DQ067623), P. septaurelia (DQ067624), P. octaurelia (DQ067625), P. decaurelia (DQ067626), P. undecaurelia (DQ067627), P. dodecaurelia (DQ067628), P. tredecaurelia (DQ067629), and P. quadecaurelia (DQ067630). The tree constructed according to the Kimura model presents two main species clusters, one comprising P. undecaurelia, P. octaurelia, P. septaurelia, and the second cluster with P. pentaurelia, P. tredecaurelia, P. quadecaurelia, P. tetraurelia, P. decaurelia, P. primaurelia, P. biaurelia. P. dodecaurelia was recovered as a separate branch. The tree constructed on the basis of the maximum likelihood method also presents two species clusters, one with P. undecaurelia, P. octaurelia, P. septaurelia, and the second with P. primaurelia, P. decaurelia, P. pentaurelia, P. tredecaurelia, P. quadecaurelia, P. tetraurelia. P. biaurelia forms a basal clade to the latter cluster, and P. dodecaurelia was recovered as a clearly distinct branch from the clusters.

Species of the Paramecium aurelia complex Sonneborn in Germany

Summary The occurrence of species of the Paramecium aurelia complex was studied in material collected in 1995 in Baden-Wurttemberg, Germany. Also five strains collected previously in Munster (Westphalia) and Stuttgart (Baden-Wurttemberg) were identified. Identification was carried out by mating the clones with the mating types of the standard strains of known species of the P. aurelia complex. The presence of P. biaurelia, P. triaurelia, P. sexaurelia, and P. novaurelia was revealed. All species were found in Stuttgart or in its neighbourhood (Baden-Wurttemberg), and two species (P. biaurelia and P. novaurelia) in the material from Munster (Westphalia). In some strains endosymbionts were found, Caedibacter sp. Preer, Preer, Jurand : (1974) in the cytoplasm, and Holospora caryophila Preer and Preer : (1982) in the macronucleus.

Seasonal and spatial variability of species occurrence of the Paramecium aurelia complex in a single natural pond (Protista, Ciliophora)

The geographic distribution and temporal occurrence of ciliates are still little known. In the present article, the occurrence of the Paramecium aurelia species complex in a natural pond situated in Kraków (Opatkowice) was investigated in different seasons in two following years. A sequence of species occurrence of the P. aurelia complex was observed. Always, paramecia were found only in some sampling points among six points sampled each time and not necessarily in the same ones. Paramecia appearing in one habitat (water body) might occupy different niches characterized by various environmental features suitable for paramecia. The following species were found in the pond: P. biaurelia, P. triaurelia, P. tetraurelia, P. pentaurelia, and P. dodecaurelia. The occurrence of some rare species (P. tetraurelia, P. pentaurelia, and P. dodecaurelia) may be connected with migrating birds which can transport paramecia with drops of water from other water bodies. If a species was observed in successive seasons or years, the possible genetic variation was investigated by analysis of sequences of LSU rDNA and mitochondrial cytb gene fragments. Among the studied species (P. biaurelia, P. triaurelia, P. pentaurelia, and P.dodecaurelia) only P.dodecaurelia showed haplotype variation in different seasons and sampling points, probably caused by the colonization of the pond by different populations of paramecia.

Studies on the Paramecium aurelia species complex in Spain (ciliophora)

Summary New habitats of Paramecium primaurelia, P. triaurelia, P. tetraurelia, and P. novaurelia are recorded from Spain. P. biaurelia and P. sexaurelia had previously been found in this area. The species of the P. aurelia complex present in Spain differ in the frequency of their occurrence and distribution. P. primaurelia dominates the other species, i.e. P. biaurelia, P. novaurelia, P. tetraurelia, P. triaurelia, and P. sexaurelia, as far as the number of designated clones and investigated habitats are concerned.

Polymorphism of Paramecium pentaurelia (Ciliophora, Oligohymenophorea) strains revealed by rDNA and mtDNA sequences.

Paramecium pentaurelia is one of 15 known sibling species of the Paramecium aurelia complex. It is recognized as a species showing no intra-specific differentiation on the basis of molecular fingerprint analyses, whereas the majority of other species are polymorphic. This study aimed at assessing genetic polymorphism within P. pentaurelia including new strains recently found in Poland (originating from two water bodies, different years, seasons, and clones of one strain) as well as strains collected from distant habitats (USA, Europe, Asia), and strains representing other species of the complex. We compared two DNA fragments: partial sequences (349 bp) of the LSU rDNA and partial sequences (618 bp) of cytochrome B gene. A correlation between the geographical origin of the strains and the genetic characteristics of their genotypes was not observed. Different genotypes were found in Kraków in two types of water bodies (Opatkowice-natural pond; Jordans Park-artificial pond). Haplotype diversity within a single water body was not recorded. Likewise, seasonal haplotype differences between the strains within the artificial water body, as well as differences between clones originating from one strain, were not detected. The clustering of some strains belonging to different species was observed in the phylogenies.