When tiny glass frogs lay down for the night, they can turn transparent hiding nearly 90% of their red blood cells.

The stained areas are hidden inside the frog’s liver, which can obscure the cells, according to a study published Thursday in the journal Science.

During the day, these little frogs spend their time hanging under the leaves of the trees. At this point, their green-colored forms cast no shadows, making them virtually invisible to potential predators.

When tiny glass frogs lay down for the night, they can turn transparent hiding nearly 90% of their red blood cells. Above: A female glass frog is pictured with eggs in her transparent ovaries, photographed from below using flash

However, when awakened, the frogs have a more reddish-brown tone.

“When they’re transparent, it’s for their safety,” said Junjie Yao, a biomedical engineer at Duke University and co-author of the study. When awake, they can actively evade predators, but when sleeping and more vulnerable, “they have adapted to stay hidden.”

Scientists used light and ultrasound imaging technology to discover a new idea: frogs are able to “concentrate” or hide nearly 90% of their red blood cells in their livers while they sleep.

This circulating blood would otherwise betray them. Yao also pointed out that frogs can shrink and squash most of their internal organs together.

The research “beautifully explains” how “glass frogs conceal blood in the liver to maintain transparency,” Juan Manuel Guayasamin, a frog biologist at San Francisco University in Quito, Ecuador, told The Associated Press. who did not participate in the study.

The stained areas are hidden inside the frog’s liver, which can obscure the cells, according to a study published Thursday in the journal Science. Above: A glass frog is perched on a leaf

Scientists used light and ultrasound imaging technology to discover a new idea: frogs are able to “concentrate” or hide nearly 90% of their red blood cells in their livers while they sleep. Above: A male glass frog is photographed from below

How they are able to accomplish this feat is still somewhat mysterious.

For most animals, having very little oxygen circulating in the blood for several hours would be lethal – and concentrating the blood so tightly would result in lethal clotting. However, the frogs are able to survive.

The researchers believe that future studies on the species could provide information for the development of anticoagulant drugs.

“Transparency is extremely rare in nature, and in terrestrial animals it is essentially unknown outside of the glass frog,” said University of Oxford biologist Richard Whitem, who did not participate. in the study.

Those that are transparent include certain fish, shrimp, jellyfish, worms, and insects, none of which move large amounts of red blood through its body.

“It’s just this really amazing, dynamic form of camouflage,” White said.

“Transparency is extremely rare in nature, and in terrestrial animals it is essentially unknown outside of the glass frog,” said University of Oxford biologist Richard Whitem, who did not participate. in the study. Above: A glass frog living in the leaves is seen

Above: A collection of photos from researchers shows the same frog sleeping, anesthetized and active (in transmitted light), showing the difference in red blood cells in the circulatory system