Glass frogs, which are native to Central and South America, are known for their unique transparent skin, which allows their internal organs to be visible. While this characteristic is normally associated with aquatic animals such as icefish and jellyfish, which do not produce red blood cells or hemoglobin, glass frogs are terrestrial and do possess red blood cells. When the nocturnal frogs are active, their blood is visible as it circulates through their circulatory system, forming a visible network of bright red veins. However, when the frogs are asleep, their bodies become almost transparent, with their blood disappearing from view.

To better understand this phenomenon, researchers at the American Museum of Natural History, Duke University, and other institutions set out to study the behavior of glass frogs while they were asleep. Using a non-invasive imaging technique called photoacoustic microscopy, which uses lasers to detect red blood cells and releases sound waves that can be used to map the frogs’ bodies, the researchers studied the animals while they were asleep and under anesthesia. They found that the frogs moved a shocking 89% of their red blood cells to their liver while snoozing.

glowing frogsThis is a highly unusual behavior, as most animals’ blood coagulates if the cells bump into each other, which can help heal a wound or, in worse scenarios, clog up a vein or artery and stop blood from flowing to crucial areas of the body. The fact that the glass frogs are able to pack their red blood cells together in this way without experiencing any negative effects is a mystery that the researchers hope to solve in future studies.

Understanding more about how the glass frogs are able to stay healthy while jam-packing their livers full of red blood cells could have important implications for blood clot research in humans. It is possible that studying the glass frogs could lead to the development of new treatments for conditions such as deep vein thrombosis, in which blood clots form in the deep veins of the body.

In addition to providing insight into the mechanisms behind blood clotting and transparency, the study also sheds light on the evolution of camouflage in animals. The glass frogs’ mirrored sacs, which encase their hearts, livers, and digestive organs, help them blend in with their surroundings and avoid being seen by predators. The researchers believe that the ability to become transparent while sleeping may have evolved as a way for the frogs to further enhance their camouflage and protect themselves from danger.

frog eggsOverall, the study offers a fascinating look at the unique abilities of glass frogs and the complex mechanisms that govern their behavior. It is a testament to the incredible diversity of the natural world and the many mysteries that remain to be uncovered by scientists.