Glass frogs can turn on their transparent appearance by hiding 90% of their red blood cells in their liver during sleep, ... it’s essentially unheard of outside of the glass frog,” White said. 3.

These little tropical frogs have a rare talent: They "hide" nearly 90% of their red blood cells in their livers while sleeping.

Using light and ultrasound imaging technology, the researchers discovered the secret: While asleep, the frogs concentrate, or “hide,” nearly 90% of their red blood cells in their liver.

These little tropical frogs have a rare talent: They "hide" nearly 90% of their red blood cells in their livers while sleeping.