A Frog Can Become Nearly Transparent While It Sleeps
Glass frogs can hide much of their blood in the liver, making their bodies more transparent at rest.
Glass frogs are known for translucent skin that reveals internal organs from below.
Research has shown that some species become even more transparent while sleeping by concentrating red blood cells in the liver.
The adaptation may help reduce the animal's visible silhouette against leaves.
Sources: American Museum of Natural History