A magic trick that even Harry Potter would be jealous of! A multidisciplinary team from the USA has now described in the specialist magazine “Science” how glass frogs use their sophisticated camouflage technology to make themselves virtually completely invisible.
The tropical frogs are nocturnal; during the day they sleep on translucent leaves. During sleep, almost all red blood cells collect in the liver and are protected from light there. This makes glass frogs two to three times more transparent than they are when awake.
As soon as night falls and the glass frogs become active, the oxygen-rich blood cells flow through the veins again. The blood and circulatory system become visible again.
Trick could one day also help sick people
But it remains a mystery how the glass frogs get so many blood cells into the liver and back into the circulation within seconds without blood clots forming or tissue being damaged. If questions about this mechanism can be clarified, it could also help people affected by vascular diseases.
Challenging: Frogs have to sleep peacefully
Only when the glass frogs sleep relaxed do they actually become transparent. When the frogs are stressed, active or stunned, they do not use their camouflage technique. That’s why the research team had to choose a method that was quiet and disturbed the frogs as little as possible. They applied what is known as photoacoustic microscopy, which uses light to detect the sound wave propagation of red blood cells. This allowed the research team to create detailed biomedical images without injecting the sleeping frogs with a contrast agent or even subjecting them to surgical procedures.