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

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

Different cells are hidden in pockets inside the frog’s liver, which hides the cells behind a mirror-like surface, a new study has found. Biologists know that glass frogs have translucent skin, but temporarily hide a bold new blood red twist for vertebrate camouflage (SN: 6/23/17).

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

What’s even more surprising to humans — prone to slime and impaired circulation — is that frogs keep nearly all of their red blood cells full for hours without clotting, says co-inventor Jesse Delia, now at the American Museum of Natural History. History of New York. The frog wakes up, and the cells just sort themselves out and iterate again.

In these latent red blood cells of glass, Taboada, Delia, and colleagues will report a double or triple transparency on Dec. 23. Science. That pale translucence may have much to do with the very snarling frogs that hid during the day, like little shadows under the leaves high in the forest canopy.

What surprised Delia was the sudden transparency of the photograph. he had studied the behavior of the glass frog, but he had not even seen it sleep. “When they go to bed, I go to bed – this has been my life for years,” he said. However, when he needed charismatic images, he put some frogs in lab dishes, and finally saw how the animals took a nap during the day.

“It was really obvious that I couldn’t see the red blood in the circulatory system,” Delia says. “I saw her stabbed – it was crazy.”

When he was planning his project to support the leader of the University lab, he was surprised to find another young researcher working in the same lab to study the transparency of glass frogs. “I was like, oh man,” Delia says. But the head of the biological optics lab at Duke, Sönke Johnsen, told Delia and her rival Taboada that they had to start with different sciences and tackle the problem together. “I think we were first,” said Delia. “Now I have him as close to family.”

To show what the red blood cells of a living frog are made of is a difficult puzzle. A light microscope would not work so that I could see through the glass as the outer tissue of the liver. And nothing that had awakened the frogs (Hyalinobatrachium fleischmann), because the red blood rushes through the body. Even anesthetizing the frogs’ liver kept the trick from working.

Delia and Taboada’s answer came from a technique called photoacoustic imaging, commonly used by mechanics. it reveals hidden interiors thanks to the subtle vibrations produced by the light, pulsating various molecules and causing the emission of small energies. The team leader Junjie Yao joined the glass frog sewing technique to the frog’s liver, taking special care not to wake the animals in the process.

Despite the glass frogs’ name, transparency among vertebrates can be much more extreme, says fish biologist Sarah Friedman of the National Oceanic and Atmospheric Administration’s Alaska Fish Science Center in Seattle. She tweeted the image in June of recently caught spoonbill spots (Crystallichthys cyclospilus), it is clear enough in most of his body tones and to show the fleshy fingers in his cradled hand. And this is not the best example. The larval stages of tarpon fish and eels, glass eels and some Asian glass catfish are “almost completely transparent,” said Friedman, who was not involved in the new studies.

But these wonders, he says, have the benefit of living water. The exquisite glass is more easily developed where there is not so sharply a visible distinction between the bodies of the animals and the aquatic houses. But the transparent body is quite cold, land or sea.