A look at Rotifers. It was by studying the Rotifer that scientists were able to determine the environmental impact of the 2010 BP oil spill. The rotifers are commonly called wheel animals. They are a phylum of microscopic and near-microscopic pseudocoelomate animals. Animals, because they have organs (cilea for mobility, a mouth with jaws, a stomach, an intestine, an anus, a bladder and foot with toes). Most rotifers are around 0.1-0.5 mm long (although their size can range from 50 ?m to over 2 millimeters). Commonly found in freshwater environments throughout the world with a few saltwater species. The rotifers in the video came from a drop of water in a rain barrel.