Paramecium duboscqui CHATTON, BRACHON, 1933. Distribution, ecology and taxonomy

Paramecium duboscqui previously has been considered a rare or even nonvalid species. During 15 years we found it in fresh, brackish and seawater of di fferent localities from Far East to the eastern coastline of the USA and fr om the Barentz coastline to Mediterranean. It is a euryhaline species with very distinct and uniform cell morphology. According to several traits, e.g . the structure of contractile vacuoles and the way of macronuclear reorgan ization, P. duboscqui should be considered as a more primitive species amon g the brackishwater paramecia. It has a preference for lower water temperat ure and is most frequently found during spring and autumn but such seasonal pattern was observed in the arctic area: White and Barentz sea shores. RAP D-PCR fingerprinting revealed three significantly different DNA patterns fo r the investigated P. duboscqui strains, Consequently P. duboscqui could be considered as a sibling species complex as it is known in P. aurelia.