Rotaria is a genus of asexual microorganism known as a bdelloid rotifer. Numerous hypotheses of rotifer interrelationships exist. The nervous system comprises about 25% of the roughly 1,000 cells in a rotifer. By contrast, the "gengoro-buna" kept in the same enclosure preferred rotifer spp. Brachionus calyciflorus is a planktonic rotifer species occurring in freshwater. It should not be confused with the rotifer superfamily of the same name. Hardy multicellular organisms (rotifer cysts) may be included to induce higher evolution. The three rotifer classes and the Acanthocephala make up a clade called Syndermata. The Frank J. Myers Rotifer Collection is the most comprehensive collection of rotifers on microslides.