Glass frogs (Hyalinobatrachium fleishmanni) stand out among amphibians for their transparency: it is so much so that the organs of these animals can even be seen through the skin. In a study published in the journal Science, experts finally discovered the secret of this feature: blood.
The study authors explain that when these frogs go to sleep, they extract 89% of their brightly colored red blood cells into crystal-lined sacs in their liver, which reflect incoming light and result in that nearly invisible appearance. The theory is that this ability helps animals avoid predators.
“Transparency is rare and very difficult because fabrics are full of things that absorb and scatter light. Red blood cells also absorb a lot of light, and we found that frogs can actually hide them by putting them in the liver.”
To understand this trick, scientists needed to use imaging techniques to quantify how transparency increases during sleep and identify red blood cells after they have disappeared inside the liver. The study also led to the understanding that sleeping glass frogs have an average of 96.6% less oxygenated hemoglobin in circulation than when they are awake.
The researchers believe that discovering the reasons behind glass frogs’ transparency could lead to advances in human medicine, as too many red blood cells in one place often form a clot, which can block a blood vessel and lead to a condition. potentially fatal, such as thrombosis. But frogs apparently can condense and expand their red blood cells at will, with no ill effects. In other words, there is a biological mechanism that prevents excessive clotting.
Source: science via National Geographic
