UNA SPECIE, DUE EMISFERI: POPOLAZIONI ANTARTICHE E ARTICHE DI PROTISTI CILIATI APPARTENGONO ALLA STESSA SPECIE BIOLOGICA

One species, two hemispheres: Antarctic and Arctic populations of ciliated protists belong to the same biological species - Microbes dwelling in oceans are of vital importance to the planet health, and their taxonomic, biological and ecological characterization is essential to better understand how the oceans are changing and how the ocean life is adapting to changes. Among a vast collection of strains of the ciliated protist, Euplotes, isolated from sediments of coastal waters in Terra Nova Bay (Antarctica), Tierra del Fuego, Greenland and Svalbard Islands, we first identified a complex of twenty strains morphologically and genetically representative of E. nobilii. These strains were then analyzed for their mating and breeding interactions and found to represent also the same biological species. Mating pairs were isolated from Antarctic and Arctic strain combinations and shown to be fully capable of completing inter- partner gene exchange and generating viable offspring. From the determination of nuclear gene sequences coding for 18S ribosomal RNA it was lastly possible to identify two Arctic strains characterized by sequence motifs specific of the Antarctic strains, thus implying that the E. nobilii populations rely on an effective inter-polar dispersion through the cold Oceanic deep currents to remain genetically connected.