When you live in an impetuous jungle you must surely find a way to survive day and night. This is the case with several animals such as frogs, some of them expel powerful toxins, and others use their camouflage to hide, but Fleischmann’s glass frogs surpass all of the above. They live in the canopy of leafy trees and have managed to adapt their camouflage to make it transparent.
Transparent Glass Frogs
Frogs are a more typical nocturnal animal, where they limit the chances of becoming another animal’s lunch; so during the day, they sleep in a leaf where their own pigmentation helps them go unnoticed.
When sunlight descends and penetrates a translucent leaf, frogs can form a clear silhouette that will attract the attention of hungry animals roaming around, which is why glass frogs, having skin and flesh that allow large amounts of sunlight to pass through, can cast a less obvious shadow.
A team of scientists from Duke University observed that to remain unnoticed, this amphibian can turn its body up to 61% transparent. In fact, if you turn these frogs upside down, you can see their heart beating since most of their body is actually invisible.
“We found that these tissues transmit more than 90% to 95% of visible light while maintaining functionality such as locomotion and vocalization. This transparency is adaptive because it camouflages the glass frogs as they sleep on vegetation during the day,” said Carlos Taboada, lead biologist of the research.
The curious thing about these glass frogs is how the red blood cells that circulate in their bodies can turn even transparent tissues opaque, something that is extremely rare in terrestrial animals, which is why these animals have become an interesting object of study.
When Do Glass Frogs Become Transparent?
For the study of this amphibian, researchers took 11 Fleishmann’s glass frogs and made use of calibrated color photography to suddenly measure their transparency at different times: when they were sleeping, awake, calling their mates, finishing exercise, and finally under anesthesia. They found that while awake, calling their partners, exercising, and under anesthesia, they maintained approximately the same levels of transparency.
However, while asleep, frogs are between 34% and 61% more transparent than when awake. Optical spectroscopy performed on the frogs has confirmed that the decrease in circulating red blood cells is the cause of the increased transparency of their lower parts, as the circulation of these cells decreased by up to 89%.
This happens so that the frogs can sleep safely; when they wake up, the cells start circulating again, and the frogs can go about their normal activities. “Whenever the frogs need to be active again, they put the cells back into the bloodstream, which gives them the metabolic capacity to move,” explained Sönke Johnsen, one of the researchers on the team.
New Knowledge in Medicine
It is not yet known how glass frogs can do this or whether it is a voluntary response to other situations. Likewise, it is also unclear whether they have any special metabolic adaptations that allow them to undergo drastic changes in circulation without damage to their organs.
The ability of glass frogs to regulate the location, density, and packing of red blood cells without clotting offers insight into human medicine as the fact that an invertebrate animal can remove nearly 90% of its blood and then restore it has some interesting implications for human health.
The fact that they can do this daily means that their blood cells may have some modifications that act against clotting, which would help develop new interventions to prevent thrombosis and cardiovascular issues.
Story originally published in Spanish in Ecoosfera
