Abstract
Glassfrogs earned their name not because they are fragile, but because they are see-through! These tropical frogs have transparent skin and muscles. When sleeping on green leaves, their bodies are almost impossible to see. This form of camouflage is rare. Most animals have colorful red blood cells that would be visible under transparent skin and give them away to predators. We used a special scanner to figure out how glassfrogs overcome this challenge. We discovered that these frogs are more transparent when they sleep than when they are active. They do this by hiding most of their red blood cells in their livers during sleep! This makes them nearly transparent to predators. Our results help explain how glassfrogs can manage this unusual kind of camouflage. This finding may also help doctors treat medical conditions in humans.