Sleeping glass frogs hide by storing most of their blood in their liver

As tiny glass frogs fall asleep for the day, they take almost 90 percent of their red blood cells out of circulation.

The colorful cells cram into hideaway pockets inside the frog liver, which disguises the cells behind a mirrorlike surface, a new study finds. Biologists have known that glass frogs have translucent skin, but temporarily hiding bold red blood brings a new twist to vertebrate camouflage (SN: 6/23/17).

“The heart stopped pumping red, which is the normal color of blood, and only pumped a bluish liquid,” says evolutionary biochemist Carlos Taboada of Duke University, one of the discoverers of the hidden blood.

What may be even more amazing to humans — prone to circulatory sludge and clogs — is that the frogs hold almost all their red blood cells packed together for hours with no blood clots, says…