Scientists Reveal the Secret Behind Glass Frogs

glass frogs
glass frogs
Courtesy of U.S. Fish and Wildlife Service Headquarters (Flickr CC0)

Scientists have finally revealed the secret behind one group of tree frogs — the glass frogs. These paperclip-size amphibians have translucent bellies which allow their insides to be seen. If they are flipped over people can see the heart pumping blood into the arteries. One can also watch food move through the glass frog’s guts.

Normally only fully aquatic creatures such as jellyfish and eel larvae are transparent. Critters that straddle land/water and terrestrial animals have a rougher time going clear. This is due to the fact that light reflects differently through the air than water.

In order to figure out the secret behind how the glass frog has see-through bellies and chests, they brought a few to the lab for observation. They used highly calibrated cameras to capture Fleischmann’s Glass Frog (Hyalinobatrachium fleischmanni). They are native to The Neotropics area and are nocturnal.

The Hyalinobatrachium fleischmanni hang out near streams throughout Central America. They feed and breed at night when they are opaque. During the daytime most of their bodies — except the lime green hue of their backs — are see-through.

glass frogs
Courtesy of Charles Sharp (Flickr CC0)

This ability helps keep them safe from snakes and spiders as they nap during the day. The green mixed with translucent skin gives the glass tree frogs a dew-like complexion on leaves. When asleep, glass frogs are between 34% to 61% more transparent than when awake, according to a report published in Science.

They are classified into roughly 160 species and 12 genera. Most of the genera are from the Centrolene, Cochranella, and Hyalinobatrachium species. They can be found anywhere from tropical lowland forests to mid-elevation mountain forests.

Recently researchers discovered that Fleischmann’s Glass Frog lacked red blood cells while resting. Carlos Taboada, a biologist at Duke University and an author of the new study stated, “We could see that there was no blood there as the animals went to sleep.” Once the amphibian woke up their blood began pumping once again.

To figure out where the red blood cells disappeared, they used a technique called photoacoustic imaging. This technique maps the ultrasonic waves produced when red blood cells absorb light.

Unlike other tree frogs, glass frogs’ livers swell by about 40% from red blood cells during daylight hours. Other tree frogs’ livers only store roughly 12% of blood cells in their liver. Glass frogs are able to store nearly all their red blood cells — 89%.

Of course, this ability raises many other questions for researchers. Like, how are they able to move so many red blood cells into one area without causing a potentially fatal clot? Or how are they able to survive without so much oxygen for 12 hours a day?

Solving these questions could potentially lead to better blood clot treatments for humans or even other possible disease cures.

By Sheena Robertson


Science: Glass frogs become see-through by hiding their blood
Britannica: Glass Frog Fleischmann’s Glass Frog

Top and Featured Image by Glass frog by Geoff Gallice from Gainesville, FL, USA, CC BY 2.0 Courtesy of U.S. Fish and Wildlife Service Headquarters Flickr Page – Creative Commons License
Inset Image Courtesy of Charles Sharp‘s Flickr Page – Creative Commons License

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