by Antonie van Leeuwenhoek in 1703. Most rotifers are around 0.1-0.5 mm long (although their size can range from 50 um to over 2 mm), and they are common in freshwater environments throughout the world with a few saltwater species.

Some rotifers are free swimming and truly planktonic, others move by inchworming along a substrate, and some are sessile,