Species of the Paramecium aurelia complex in Japan.

In Japan, the presence of Paramecium sexaurelia was revealed for the first time, and a new habitat of P. tetraurelia was found there.     

Paramecium dodecaurelia strains from Hawaii

The presence of Paramecium dodecaurelia (three strains) was recorded in Hawaii.     

Paramecium tredecaurelia of the Paramecium aurelia complex in Israel

The paper concerns the finding of a new habitat (Kiryat Motzkin, north of Haifa, Israel) of Paramecium tredecaurelia from the P. aurelia complex. This is only the forth known locality of the species in the world. Previously, its strains were obtained from widely separated localities: the River Seine, Paris, France; Benenitra, Madagascar, and the Cuernavaca Valley, Taxco, Mexico. The studied strain originating from Israel was identified as P. tredecaurelia on the basis of the strong (90%) conjugation between the complementary mating type of the examined clones with the appropriate standard strain 209 of P. tredecaurelia from Paris, France (restricted to odd mating type). However, the strain from Israel is restricted to the even mating type.     

Paramecium sexaurelia of the Paramecium aurelia species complex in Thailand

The clones originating from Thailand, Phuket Island, were identified as Paramecium sexaurelia.     

Species of the Paramecium aurelia complex in Italy

New stands of Paramecium pentaurelia were recorded in Valmarana, Veneto region in Italy and one stand of P. primaurelia was found at the same locality.     

The Paramecium aurelia species complex in Ukraine

New habitats of Paramecium biaurelia were found in the Gorgany Mts, Eastern Carpathians.     

New Paramecium quadecaurelia strains (P. aurelia spp. complex,Ciliophora) identified by molecular markers (rDNA and mtDNA)

Paramecium quadecaurelia is a rare species (previously known only from two locations) belonging to the P. aurelia species complex. In the present paper, fragments of an rDNA gene (ITS1-5.8S-ITS2-5′ rDNA) and mtDNA genes (cytochrome oxidase subunit I and cytochrome b regions) were employed to assist in the identification and characterization of three new strains collected from Ecuador and Thailand. Molecular data were confirmed by mating reactions. In rDNA and mtDNA trees constructed for species of the P. aurelia complex, all P. quadecaurelia strains, including the three new strains discussed in this study and two known previously from Australia and Africa, form a monophyletic but differentiated clade. The present study shows that genetic differentiation among the strains of P. quadecaurelia is equal to or even greater than the distances between some other P. aurelia species, e.g., P. primaurelia and P. pentaurelia. Such great intra-specific differentiation may indicate a future splitting of the P. quadecaurelia species into reproductively isolated lines.     

Species of the Paramecium aurelia complex in the middle Sudeten of Czecho-Slovakia.

On the investigated territory three species of the complex were identified, namely Paramecium biaurelia, P. triaurelia, and P. novaurelia. P. novaurelia dominated over the other species with regard to the number of clones established from nature as well as to habitats.     

Further studies on the Paramecium aurelia species complex in Greece

The strains collected in Athens and the city of Egina, the Island of Egina were identified as P. primaurelia. This is the first information about finding of P. primaurelia in Greece.     

Anatomy of mitochondrial DNA from Paramecium aurelia

Summary The linear genome of mitochondrial DNA from four species of Paramecium aurelia was investigated with respect to restriction endonuclease fragments, location and number of ribosomal RNA genes, and interspecies EcoRI and HindIII fragment homologies. One copy of each of the rRNA genes was found in all four species and the 14s and 20s rRNA genes were separated by at least 3,000 bp. R-Loop analysis of the 20s rRNA gene did not reveal the presence of an intervening sequence. Interspecies homology studies showed species 1, 5, and 7 to have a high degree of homology but species 4 was less than 50% homologous to species 1 mt DNA. For all four species, rRNA genes showed good homology indicating that these DNA sequences are highly conserved, even between species having many non-homologous regions. A major region of DNA which displayed little homology between species 1 and 4 was that fragment containing sequences essential for initiation of DNA replication.     

Studies on macronuclear DNA from Paramecium aurelia

Macronuclear DNA was isolated from purified macronuclei of Paramecium aurelia and the size distribution was determined with regard to growth phase and method of extraction. DNA molecules as long as 105 microns and as short as 0.2 microns were observed. It was concluded that the method of extraction affected the observed length of DNA extracted and that macronuclear DNA isolated from cells in balanced growth was less susceptible to nuclease degradation than was DNA isolated from cells in stationary phase. Renaturation studies were performed on macronuclear DNA and a kinetic complexity of 22-times E. coli DNA was determined. This value was similar to those values reported for Tetrahymena and Stylonychia macronuclear DNA. Correcting for GC base content yielded a kinetic complexity for Paramecium macronuclear DNA of 11-times E. coli DNA which corresponded to 3 X 10(10) daltons. There would be about 1400 copies of a unit genome of this complexity within each newly replicated macronucleus. Density gradient analysis indicated that the genes coding for ribosomal RNA had a greater density in CsCl than the bulk DNA. Molecular hybridization studies indicated that the genes coding for 25 S RNA represented 0.14 percent of the total macronuclear DNA. Correcting for GC base content, this corresponded to 30-35 25 S RNA genes per unit genome. These results on Paramecium are discussed in relationship to other ciliate macronuclear DNA.     

Electrophoretic karyotype polymorphism of sibling species of the Paramecium aurelia complex

Variability of karyotypes is one of the main mechanisms of speciation in organisms. Electrophoretic karyotypes of the macronucleus (MAC) obtained by pulsed-field gel electrophoresis were compared for 86 strains of all 15 sibling species of the Paramecium aurelia complex in order to determine if karyotype differences corresponded to biological species boundaries. Because the electrophoretic karyotype of the MAC reflects indirectly the frequency and distribution of fragmentation sites in the micronuclear (MIC) chromosomes, any change in MAC electrophoretic karyotype may be a marker of certain chromosomal mutations in the MIC. Thirteen main variants of electrophoretic MAC karyotypes were observed in this species complex. Ten of them appeared to correspond to biological species, while the three other variants characterized several species each. Intraspecific polymorphism was observed for several species: in some cases a certain variant of MAC karyotype was specific for all strains from the same part of the world. Distribution of the MAC karyotype variants along molecular phylogenetic trees of the P. aurelia complex shows that isolation of each species or group of species of this complex was accompanied by divergence in the molecular organization of the genome.