A class of the phylum Rotifera characterized by paired gonads and obligately asexual reproduction, found in diverse freshwater habitats worldwide. Bdelloid rotifers are among the most common microinvertebrates, particularly in ephemerally aquatic environments such as rain gutters, bird baths, moss, lichen, and detritus. First observed by A. Leeuwenhoek more than 300 years ago, bdelloids have long been a favorite subject of amateur microscopists and can easily be isolated and observed with a low-power microscope.