Tiny glass frogs can become transparent at night by concealing nearly 90 percent of their red blood cells.
The colorful regions are tucked away inside the frog’s liver, which can conceal the cells, according to a study published in Science on Thursday.
These little frogs spend the daytime clinging to the underside of tree leaves. At that point, their green bodies no longer throw shadows, rendering them nearly invisible to predators.
However, once they awaken, the frogs’ coloring becomes more reddish-brown.
“When they are transparent, it is for their protection,” said Junjie Yao, a biomedical engineer at Duke University and co-author of the study. When they are awake, they can actively avoid predators, but when they are asleep and most vulnerable, they have adapted to hide.
Using light and ultrasound imaging technologies, scientists discovered that frogs can ‘concentrate,’ or hide, over 90 percent of their red blood cells in their liver while sleeping.
Otherwise, their circulating blood would give them away. Yao also noted that most of the frogs’ internal organs can contract and become compacted.
Juan Manuel Guayasamin, a frog biologist at the University San Francisco of Quito, Ecuador, who was not involved in the study, told the Associated Press that the study “beautifully explains” how “glass frogs conceal blood in their liver to retain transparency.”
How they can execute this feat remains a mystery.
For most animals, having very little oxygen-carrying blood circulate for several hours would be lethal, and such a high concentration of blood would result in fatal clotting. The frogs are however able to live.
Researchers anticipate that future research on the species could lead to the creation of anti-blood-clotting drugs.
Richard White, a biologist from Oxford University who was not involved in the study, remarked, “Transparency is extremely rare in nature, and in terrestrial animals, it’s practically unheard of”
Some fish, shrimp, jellyfish, worms, and insects are transparent, and none of them circulate vast amounts of red blood through their bodies.
White stated, “It’s a truly remarkable, dynamic sort of camouflage.”
