Phylum:
Class:   Eurotatoria
Order:  Bdelloidea
Commonly known as:  Wheel or whirling animals
Commonly found in:  Brackish or marine habitats, still water such as lake bottom, in soil, or on mosses.
Mobility: Sessile (immobile)
Reproduction: Sexually or parthenogeneic.

Rotifers are planktonic, size ranges from 1mm-3mm and may have different body shapes such as sac-shaped, spherical, cylindrical, wide and flattened, or long and slender and colorless body. The body of rotifers is divided into three parts – head, trunk, and foot. Head region contains coronal cilia that produce water currents which helps in drawing the prey towards the buccal field or sometimes they have spines or bristles in place of cilia which prevent prey from escaping. Body is annulated that is ring shaped which provides flexibility to organism to capture the prey. They feed on small animals, algae, organic matter, also some species act as parasitic on crustaceans, protists, snail eggs. Whereas the adult rotifers and their eggs act as prey for long tailed ducks, copepods, nematodes. Creeping motility is observed while catching the prey by secretion of pedal glands which  helps in attaching or cement the foot to the surface and extending the body with the help of annulation that helps to draw head towards the prey. Life span is about 6 to 45 days. It is said that presence of rotifers in activated sludge, provides the good oxygenated water.