The mystery of why glass frogs are see-through skin has been solved, scientists say: the unusual feature is a type of camouflage.
The frogs of glass are found in the tropical zone of Central and South America, and they get their name from their skin.
However, the frogs are not truly transparent, but translucent, with the skin of his back, typically, a rich green, and their intestines and the heart are visible through her belly. This has led to a question that has kept scientists in the hop.
“If the predators can not see them directly, despite of the frogs, why is the glass frogs have transparent skin at all, and not the opaque camo patterns of other tree frog species?”, said Dr. James Barnett, a postdoctoral researcher at McMaster University, Canada, who is co-author of the study.
Barnett and his colleagues say they have deciphered the riddle. “The frog is always green, which generally coincide with the leaves, but the leaves differ in its brightness,” said Barnett. The team say that while the color of the frog’s body with very few changes against the darkness or the light foliage, the legs are more translucent and hence the change in brightness, helping the amphibians to the other.
“To have translucent legs and rest with your legs around the body, the frog, the edge is transformed into a softer, less contrast gradient from the leaf to the legs, and again of the legs to the body,” said Barnett, pointing out that this makes the frog contour of less recognisable to predators.
Writing in the US journal Proceedings of the National Academy of Sciences, Barnett and his colleagues report how they carried out three experiments.
In the first, they photographed 55 frogs of glass both in the leaves and on a white background, and then used computer models to compare the color of the frog in each stage. “We have found that the color of the frogs’ bodies do not change much between cultures, but the legs did change in a significant way,” said Barnett, adding that the change was a change in the brightness, not the hue.
The results were the same when modeling how the different species you can see these frogs, including a snake, a bird and a human. “The camouflage effect is interpreted in a similar manner between human beings and the frogs’ natural predators,” said Barnett.
The team then produces computer-generated images of frogs of glass with different patterns of translucency against the leafy background. Twenty people were presented with 125 pictures and asked to point out the frog as soon as possible. The team found that participants were faster to detect the frog when it was completely opaque in comparison with the frogs with a natural pattern of translucency.
Finally, the team of 180 translucent and 180 dull frogs of the gelatin and put them in the vegetation at the Equator, the follow-up in the course of 72 hours if the frogs were attacked by birds. In general, the 53 opaque and 24 translucent frogs are eaten during the experiment.
“Our study shows that the be translucent help of glass frogs to camouflage themselves from predators, but not necessarily in the form expected by comparison with the full transparency of the species,” said Barnett.
Prof Devi Stuart-Fox, an expert in animalcolour and behavior at the University of Melbourne, who was not involved in the research, said: “This is a fascinating study because it shows another form of camouflage in animals – the great diversity of strategies of camouflage in nature is truly remarkable.”
Stuart-Fox said that all three of the experiments had limitations, but all in all, the evidence was compelling that the frogs ‘ translucency is a form of camouflage.
“Interestingly, the legs are more translucent than the body, so that the edges of the body more difficult to distinguish,” she said. “The predators form a search image for the shape of its prey, to mask the body of the outline is a very effective strategy to improve the camouflage.”