Frogs are one of the most diverse animal groups, with a wide range of sizes and colors. Scientists have identified up to 5,000 frog species and believe there are many more waiting to be discovered.

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Among all the known species, glass frogs are the most peculiar ones, as they hone the ability to turn themselves transparent. Transparency is a rare trait in wild, with most ocean-based animals possessing it. Surprisingly, it is also very uncommon among land-based animals.

Related: First fluorescent frog in the world found in South America

As a result, the scientific community has taken a keen interest in this unique trait. Scientists have been trying to figure out how glass frogs become transparent. And recently, they have deciphered how they do so.

According to a study in the journal Science, glass frogs “conceal blood in their liver to maintain transparency.” 

But why do they do this? The nocturnal frog sleeps on green leaves during the day, making it vulnerable to predation. To avoid being noticed by birds and other predators, the species turn on and off their transparent look, thus making them almost invisible on the leaf. 

However, once awake, the frogs’ color changes to an opaque reddish-brown, according to the study. The glass frog can be found in South and Central America.

For this study, the team of researchers from Duke University used light and ultrasound imaging technology to examine this characteristic among glass frogs. Researchers observed the frog while it was active and sleeping. It was discovered that this frog species can hide approximately 90% of its red blood cells in its liver. What’s most startling is that the other creatures that turn transparent — such as fish, shrimp, jellyfish, worms and insects – do not move this large amount of red blood together.

According to the team, it is unclear how they do this, let alone survive it! They claim that this process is deadly and often results in blood clotting due to decreased blood circulation and tightly packed blood cells. The researchers believe that this type of camouflage is unique to glass frogs. Interestingly, understanding this unusual ability could also aid in the development of anti-clotting medications.

A multidisciplinary team of biologists and biomedical engineers carried out the research. The findings have been published in the scientific journal Science. 

Via Science

Lead image via Jesse Delia