Preface: Diverse rotifers in diverse ecosystems.

The XVI International Rotifer Symposium took place in Zagreb, Croatia in 2022. The symposium was organized every four years instead of the usual three due to global and regional circumstances, and it was held in a hybrid format. The conference was supported by the University of Zagreb, the Faculty of Science, the Croatian Ecological Society, and sponsors such as Springer Nature and domestic companies/associations. The event included social events and excursions to cultural and natural sites in Croatia. A total of 141 participants from 25 countries attended, with 97 onsite and 44 online. The symposium featured invited lectures, presentations from young scientists, and special sessions and workshops on various topics related to rotifers. These included practical techniques for capturing images of rotifers, the importance of culturing rotifers for ecological experiments, and the establishment of a database for rotifer research. There were also sessions on the ecology of rotifers in specific regions and their reproductive processes. The special issue of Hydrobiologia includes 28 articles on rotifers, covering themes such as evolution, general ecology, biotic interactions, and environmental stressors. The article also pays tribute to prominent rotifer researchers who have passed away. [Extracted from the article]