Differential interference contrast (DIC) light micrograph of a Keratella sp. planktonic rotifer. Keratella rotifers have a strong armour into which the wheel organ is retracted in case of danger. The focus in this image is on the surface of the carapace. A red eye spot is visible below the rotifer. The animal is framed by several Spirogyra sp. green alga filaments. Magnification: x420 at a print width of 10 centimetres.