Rotifer. Polarised light micrograph of a Ptygura sp. rotifer. Rotifers are common multicellular animals found in pond water. This species is a sessile rotifer. It builds a protective tube from its own secretions and surrounding detritus, from which a corona of beating hair-like cilia protrudes, creating a current that sweeps food into the mouth. Magnification: x200 when printed 10 centimetres wide.