Seasonal and spatial variability of species occurrence of the <Emphasis Type="Italic">Paramecium aurelia</Emphasis> 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.