Rotifers are small, pseudocoelomate metazoans, the size of ciliates. The name derives from the ciliated corona, which doubles as a feeding / locomotor organ. The pseudocoel functions as a hydrostatic skeleton. In some species, contraction of the surrounding muscles allows the animal to extrude the food crushing mastax, which it then uses to grab small protozoans and other food objects. In the specimen at the right, the corona has been modified into a food trapping organ. For rotifer micromovies, go here.