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

The animals up their transparency by packing away red blood cells with no ill effects

This sleeping female glass frog tucks away most of her red blood cells while she sleeps. Her eggs are visible within her transparent ovaries.

This sleeping female glass frog tucks away most of her red blood cells while she sleeps. Her eggs are visible within her transparent ovaries.

Jesse Delia

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.