A giant leap for blood clot research?

Scientists uncover glass frogs’ unique vanishing act - becoming see-through by hiding their blood - opening new avenues for blood clot research and medicines.

By hiding almost all of their bright-red blood in a unique mirror-coated liver when they are sleeping, glass frogs more than double their transparency without suffering from blood clots. Picture: News Corp

When glass frogs fall asleep in the trees of the tropics they fade from view. The muscles and bellies of these small amphibians become translucent, hence their name.

Now scientists have discovered how they perform this vanishing act: by hiding almost all of their bright-red blood in a unique mirror-coated liver.

This makes much of the frogs’ bodies see-through, which helps them to hide from predators.

The findings could open new avenues of research into blood clots, which the frogs somehow avoid even though they regularly cram about 90 per cent of their red blood cells into their livers each day.

“There are more than 150 species of known glass frogs in the world, and yet we’re really just starting to learn about some of the really incredible ways they interact with their environment,” said Dr Jesse Delia of New York’s American Museum of Natural History, a co-author of the study, which has been published in the journal Science.

The frogs, which live in the American tropics, are nocturnal. They spend their days sleeping upside down on translucent leaves that match the green colour of their backs, providing camouflage.

Their undersides, however, are covered in translucent skin and muscle, which allows their bones and organs to be seen. Researchers believe that this helps mask the frogs from predators.

In particular, their see-through legs, which surround the body as they rest, soften the frogs’ outline.

However, being transparent is tricky for vertebrates, in part because their circulatory system is full of opaque red blood cells.

NEW RESEARCH: Glass frogs are masters of camouflage. Translucent skin helps hide them from foes. But can these amazing amphibians offer insight into blood-clot research? 

Check out this study by Museum scientists & researchers at @DukeU to learn more: https://t.co/3W189Mzqsrpic.twitter.com/8OIG4OMJmR

— American Museum of Natural History (@AMNH) December 22, 2022

Studies have found that some other animals - including ice fish and larval eels - achieve transparency by not producing haemoglobin, a protein that carries oxygen and makes blood cells red. The frogs use a different strategy.

“Glass frogs overcome this challenge by essentially hiding red blood cells from view,” said Carlos Taboada of Duke University, another co-author of the study.

The researchers used a technique called photoacoustic imaging, which uses light to induce red blood cells to produce sound waves. This allows researchers to map the location of the cells within sleeping frogs without touching them or sacrificing them. This was important because glass frog transparency is disrupted by activity, stress, anaesthesia and death.

The researchers focused on one particular species of glass frog, Hyalinobatrachium fleischmanni. They found that resting frogs could double or treble their transparency by removing nearly 90 per cent of their red blood cells from circulation and packing them within their livers, which contain reflective guanine crystals. These give the organ a mirror-like quality, helping it to blend into the background.

When the frogs need to resume activity, they bring the red blood cells back into the rest of the body, which enables them to move around. When this happens, the opaque cells reduce the frogs’ translucence.

In most vertebrates, gathering together large amounts of red blood cells would raise the risk of dangerous blood clots forming in veins and arteries. But not in glass frogs.

The researchers believe that the frogs may have a secret that could help develop new anti-clotting medicines for people.

“This is the first of a series of studies documenting the physiology of vertebrate transparency, and it will hopefully stimulate biomedical work to translate these frogs’ extreme physiology into novel targets for human health and medicine,” Delia said.

The Times