A Molecular Survey of Paramecium dodecaurelia (Ciliophora, Protozoa) Strains from a Single Pond

The aim of the study was to investigate if strains of P. dodeaurelia collected from different sampling points situated around the single habitat (a pond in Dr Jordan's Park, Krakow, Poland) and originated from successive seasons may be characterized by different haplotypes. So, we expected the spatial and seasonal differentiation of P. dodecaurelia haplotypes originated from a single habitat, as the studied species is characterized by high intra-specific polymorphism. Fragments of 5'LSU rDNA (349 bp long) and COI mtDNA (309 bp long) of 18 strains of Paramecium dodecaurelia were compared, five of these came from the studied pond (strains A, B, C1, C2, C3) and others from our collection originating from Europe (Italy, Germany, Russia, Ukraine), Asia (Kazakhstan, Russia Eastern Siberia [RS], Japan), island of Tenerife, mainland USA and Hawaii.The following species were used as outgroups: a standard strain of P. pentaurelia (87, from Pennsylvania, USA), a representative of the P. aurelia complex showing no intraspecific differentiation; and P. caudatum, a representative of a different Paramecium morphospecies. A comparison of the distance matrix did not show any variability among strains from Krakow. The same haplotype appeared in several strains from Europe (RM, RV, RY, UV, IE, Poland), Asia (KA, RS), and Tenerife (TE). A different haplotype was detected in the other European strains from Germany and Italy (TR). Strains from USA, Japan, and Hawaii were more distant from other P. dodecaurelia strains. Polymorphism of P. dodecaurelia was confirmed, however, no correlation was found between geographical origin and genetic distance of strains. The strain from Trento, Italy of P. dodecaurelia revealed the same haplotype as strain 87 of P. pentaurelia, in spite of sexual isolation of both species. Perhaps, speciation of P. aurelia complex proceeds by a different way than differentiation of studied DNA fragments and relationships of species of the P. aurelia complex is more complicated that was expected. It may be connected with the origin of the P. aurelia complex. The hypothesis on the origin of the complex, proposed by Aury et al. (2006), is presented in discussion.