Glassfrogs turn transparent by concealing red blood cells in liver, a study finds

Scientists have discovered the trick behind one of the animal kingdom’s best-known disappearances. Further research could lead to a life-saving drug for humans.
According to a study published on Thursday, mirror frogs have implemented invisibility cloaks.

Studying paperclip-sized amphibians — known for their thorax and abdomen — could have major implications for human medicine as well.

What did the researchers find?
A team of scientists from Duke University in North Carolina, USA conducted research on frogs native to Central and South America.

According to the findings, published in the journal Science, the researchers brought several glass frogs into their labs and used highly calibrated cameras to study the tiny amphibians.

They discovered that the frogs are usually opaque at night when they are feeding and breeding.
A glass frog’s heart and other organs can be seen beating through its transparent chest and abdomen Image: AP/Image Alliance via Jessie Delia/AMNH

However, during the day they hide rusty red blood cells in their livers – which appear like snowdrops on the green leaves they rest on – to protect themselves from predators.

The livers of these frogs swell up to 40% of their volume during sleep to cover 89% of the blood, the researchers report in Science.

That’s far more than tree frogs, which can store only 12% of their blood in the organ, according to a Science Journal article on research.

Transparency in nature is often seen in aquatic organisms such as eel larvae or jellyfish.

Animals that live on land, part or all of the time, do not possess this power because light is reflected differently by air than by water. Red blood cells get their red color because the protein in hemoglobin absorbs light.
Glass frogs can secrete nearly 90% of their blood in their livers when they sleep, researchers Image: AP/Image Alliance via Jessie Delia/AMNH

Glass frogs seem to have overcome that barrier. The study found that cold-blooded animals were 34% to 61% more transparent when resting than when active. As the frogs woke up, blood began pumping through their veins again, making them opaque.

What are the implications for humans?
How glass frogs pull off their transparency trick without dying remains a mystery.

Experts explained that such a small blood flow in the body for several hours can be dangerous for other animals as tight blood flow to an organ can lead to fatal blood clots. Yet, the frogs survive.

Carlos Tabota, co-author of the study, told The Associated Press (AP) that further research on the terrestrial animal could lead to the discovery of anti-clotting drugs for humans.

Thrombosis is a leading cause of death worldwide, with one in four dying from complications from blood clots or blood clots.

The discovery takes researchers a step closer to finding a cure for malignant tumors.

“This fundamental observation about mirror frogs leads to very clear implications for human health,” said oncologist Richard White of the University of Oxford, who separately studied translucent zebrafish.

This report was written in part with content from The Associated Press.