Biogeography and ecology of Rhizodomus tagatzi, a presumptive invasive tintinnid ciliate

Following the recent redescription of Rhizodomus tagatzi, we carried out a comprehensive study of the biogeography and ecology of this tintinnid ciliate based both on original data and a critical review of the literature. The data indicated that R. tagatzi is a neritic tintinnid ciliate, which has been reported, to date, only from the Northern Hemisphere at tropical to warm-temperate latitudes. It has most often been detected in estuaries or lagoons characterized by a high trophic level and stable water column, and typically in the seasonal periods of highest abundance of small-sized phytoplankton. The biogeographic pattern emerging from this study, along with the prevalence of this species in ports and in transition environments exploited for bivalve culture, confirms the former assumption of an invasive behaviour of R. tagatzi, and suggests aquaculture transplants as a possible means of dispersion for ciliated protozoa.