A group of sleeping glasses on a single leaf stirred, revealing their camouflage.
Jesse Delia
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Jesse Delia
A group of sleeping glasses on a single leaf stirred, revealing their camouflage.
Jesse Delia
Jesse says Delia happened in Panama. A few years back he completed his field work – a research project exploring the behavior of parents of the glass type. He brought a few of these transparent, half-dollar-sized frogs to his lips for a photo.
It leads to an exciting discovery.
“Delia tells NPR some photos of the beautiful colored glass.” He placed them in a petri dish and saw each frog’s circulatory system translucent through the skin — “with red blood cells.”

But when he later returned, the frogs were asleep and the blood had “gone”.
As if the arteries and veins had melted. “I thought he was crazy,” recalls Delia, now a biologist at the American Museum of Natural History in New York.
He took a vitreous image of the beating heart and sent it to his longtime supporter, Carlos Taboada, a biologist at Duke University.

“It was colorless,” Taboada said. Nor was the telltale red line of vessels in the frog’s belly visible. “It was crazy. I’d never seen anything like it.”
Both Delia and Taboada wanted to know — Where would all the red blood of the frogs go?
In the new paper in the newspaper ScienceTaboada, Delia and their supporters offer an answer: “Most red blood cells hide in the liver,” Delia explains.

The same vitreous was photographed while asleep (left) and while active (right), showing the difference in red blood cell circulation.
Jesse Delia
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Jesse Delia
The same vitreous was photographed while asleep (left) and while active (right), showing the difference in red blood cell circulation.
Jesse Delia
During the day, while they sleep in the glassy green leaves, they are vulnerable to predators, so they become transparent camouflage. (Their gills, among other organs, are covered in highly reflective white crystals.) Since red blood cells carry little oxygen, Delia says frogs likely have “some sort of process that allows them to keep those cells alive in the open.” Then at night, when the frogs become active, “feeding and mating, going about their normal business,” the glass amphibians release red blood cells into the circulation.

Taboada says the frogs “have 90% of their red blood cells roughly in a really, really small volume. Basically these conditions can cause some coagulation disorders.” Researchers say that knowing how the vitreous humor avoids the blood clotting cascade could pave the way for new anticoagulants in humans.
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