Recently, however, researchers have uncovered the mystery of how transparent glass frogs’ skin works.

According to scientists, see-through glass frogs are not an example of true transparency, because glass skin is not evenly distributed over their bodies, most of which is found on the underside. of the body while the skin on the back has a greater amount of pigment.

A new study examining this imperfect transparency suggests that the feature observed in glass frogs is better described as "transparency." This may be an unknown type of camouflage mechanism in animals.

Behavior ecologist James Barnett from McMaster University in Canada explains: “It’s relatively common in aquatic species where animal tissue shares a refractive index - the speed of light passing through it - with water. around".

On land, animal transparency is a rarer phenomenon, glass frogs and glass butterflies are the most representative.

But while the see-through of some butterflies and moths is said to offer the advantage of hiding from predators. Scientists are not clear whether the semi-transparency of glass frogs has similar camouflage benefits. In glass frogs, transparency seems to serve a very different purpose.

"The frogs are always green but seem to be light and dark depending on the background. This change of brightness makes the frogs closer to their immediate surroundings, they are mostly made up of. from green leaves, ”Barnett said.

The effect amplified on the legs is more translucent than the skin on their upper parts. When the glass frog rests on a green backdrop, its legs rest to the sides, the translucent limbs act as visual buffers, softening the contrast of colors between the shades of green. Different tree of frog body and leaf it is sitting.

"This creates a diffuse slope from leaf color to the color of the glass frog rather than a sharper edge," Barnett adds.

This disguise mechanism researchers call "edge diffusion" seems to be more than just a hypothesis. In an experiment designed to determine the degree of translucency in the effect of hiding glass frogs, more than 50 frogs were photographed on both green and white leaves, while computer models (simulated possible). vision of animal predators and humans) tried to distinguish amphibians.

Tests show that the perceived glare - the intensity of the light emitted - of the frogs varies depending on the platform on which they are against.

This change in luminance then transforms the striking high-intensity outline of the frog into a more conspicuous boundary. Therefore, the imperfect clarity of glass frogs provides effective camouflage, camouflage the frog’s borders, and blends frogs and leaves more smoothly together.

In another experiment, participants had to spot frogs in computer-generated images of animals adjusted to display different amounts of blur. In general, participants quickly identified frogs with more opaque characteristics than frogs.

Finally, to test whether the ability of translucent camouflage offered a survival advantage in the wild, the team created hundreds of fake frogs made from gelatin, half translucent and half opaque. through the use of food dyes.

These artificial amphibians were dropped on a site in Ecuador, where glass frogs were popular, and left for 72 hours. At the end of the experiment, translucent models were eaten more than opaque frogs. This shows that glass frogs get the advantage of camouflage thanks to their semi-transparent bodies.

"In fact, we are just beginning to shed light on how the different forms of camouflage really work. Glass frogs illustrate a new mechanism that we haven’t really considered before," Behavior ecologist Innes Cuthill from the University of Bristol in the UK explains.