Fast and Accurate Identification of European Species of the Paramecium aurelia Complex by RAPD-Fingerprints

Abstract

Ciliates of the genus Paramecium have a unique cortical pattern after silver staining, and can be easily identified as paramecia in any sample from small ponds or other freshwater collection areas. Furthermore, readily detectable morphological characteristics serve as guides to distinguish between species of paramecia by light microscopy of living cells. Alternatively different species of the P. aurelia complex appear morphologically identical, often despite striking differences in their ecology or life strategies. This has severely hampered ecological studies [field work]. There are only a few data sets available concerning the ecology of free living paramecia in natural habitats, because there is no feasible method for multiple determinations of Paramecium species that are often required during field studies. With the adaptation of the Random Amplified Polymorphic DNA–Polymerase Chain Reaction (RAPD–PCR) fingerprint technique, we succeeded in performing a fast and simple identification of European Paramecium aurelia species. We developed a 10-mer random primer that generated fingerprints highly specific for nine different P. aurelia species. The diagnostic band pattern was the same for different stocks of the same species, despite different geographic origins. This method has already been used successfully to identify some unknown clones collected from natural environments in southwestern Germany. This technique can be used for the identification of species and for studying elements of population structure. Field studies are now possible to answer basic questions concerning the ecology of Paramecium. These are necessary to develop a general model for limnological processes in freshwater ecosystems at a scale of a 100-μm organism.