This X-ray shows the mouth on the underside of a white-rimmed stingray (Himantura signifer). The ray feeds without seeing its prey. Its eyes are on the top of its body, while its mouth is on the bottom. This rarely recorded freshwater species is known from about 10 specimens in museum collections. 

Scientists in the Division of Fishes at the Smithsonian's National Museum of Natural History use X-ray images, like the one shown, to study the complex bone structure and diversity of fish without having to dissect or damage the specimen.

The National Museum of Natural History is currently exhibiting "X-Ray Vision: Fish Inside Out," a temporary exhibit that showcases fish evolution and diversity through 40 black and white X-ray images prepared for research purposes. Experience the exhibit at the Museum until August 5, 2012 or online on the Encyclopedia of Life.