Bdelloid Rotifers, a species of freshwater animals that can survive radiation doses up to 1,000 times greater than the lethal dose for humans, are found to be so small that they can barely be seen. They are complex animals with muscular pharynges, ciliated structures used for movement and feeding, and even entire organ systems. Despite their small size, bdelloids can repair DNA damage that would be catastrophic in most other animals without medical intervention. Their radiation resistance appears to be tied to their ability to survive desiccation (drying out completely), which also helps them withstand ionizing radiation. Researchers have discovered that their DNA repair machinery is also effective against radiation-induced DNA breaks.