Going down the rabbit hole: insight into the future of <i>Paramecium</i> (Ciliophora, Protista) biodiversity surveys

Paramecium , a research subject in many areas of life sciences, appeared to be a ciliate genus with a well known biodiversity structure. However, the understanding of its biological diversity has been evolving rapidly in recent years, driven by the discovery of new taxa and an expanded knowledge of the distribution of known species. Most future insights into Paramecium biodiversity are expected to come from molecular data, particularly through eDNA sampling. As one of the most recognisable microeukaryotes, commonly found in freshwater ecosystems, and with over a century of biodiversity research – including extensive reference data from GenBank records and living culture collections – Paramecium holds significant potential to become a model ciliate for studies in biodiversity and biogeography. This review addresses the challenges of species identification within the Paramecium genus, the current state of knowledge on its biodiversity and other factors that may shape future research. Despite some existing bottlenecks, new approaches to data acquisition and analysis will enable researchers to integrate diverse lines of evidence, allowing for exceptional explorations of Paramecium species and populations.