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Glass Act

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    Predators passing overhead won’t notice this frog. Glass frogs have the rare ability to turn on and off their nearly transparent appearance. (Jesse Delia/AMNH via AP)
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    A group of glass frogs sleep together upside down on a leaf. (Jesse Delia/AMNH via AP)
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    Researchers measured and photographed the frogs’ transparency during different activities. Notice the difference in red blood cell circulation! (Jesse Delia/AMNH via AP)
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    Glass frogs sleep, forage, fight, and raise babies on leaves over tropical streams. (Jesse Delia/AMNH via AP)
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    This male frog is protecting the eggs that a female laid on a leaf. (Jesse Delia/AMNH via AP)
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Certain frogs in South and Central America possess a rare superpower. The Creator provided a way for them to become invisible. Now a study of northern glass frogs could someday help humans too.

After dark, a species of nocturnal (active at night) frog hops around. Blood pumping in the frogs’ see-through green bodies produces a red-brown color.

During the day, the sleepy frogs hide under tree leaves. Dozing and defenseless, they would seem easy prey for hungry birds. Because they have transparent skin, the frogs’ moving blood would give them away.

Instead, the one- to one-and-a-half-inch amphibians blend into the leaves. Their blood “disappears,” making them nearly invisible!

“When they’re transparent, it’s for their safety,” says Junjie Yao, a Duke biomedical engineer and co-author of the glass frog study.

Co-author Jesse Delia helped collect frogs for the study. He wondered where a glass frog’s blood went at night.

Using light and ultrasound imaging, Delia and other Duke researchers discovered the froggy secret: While asleep, glass frogs “hide” 89% of their red blood cells in their livers. In fact, the livers of glass frogs grow as much as 40% larger when storing blood.

That’s not all!

Biologist Sönke Johnsen has a front-row seat to God’s cloaking skills. He studies animal transparency at Duke. Johnsen’s team found that glass frogs’ organs sit inside a light-reflecting sheath. Johnsen calls the frogs’ livers “mirror-coated.” More God-designed camouflage.

The Duke research “beautifully explains” how “glass frogs conceal blood in the liver to maintain transparency,” says biologist Juan Manuel Guayasamin.

Scientists are still researching glass frogs. They want to know how the frogs transport and store large amounts of blood—and why the action doesn’t kill them or cause fatal clotting.

Further study could benefit human healthcare. Anti-clotting medicine may be one outcome, says Carlos Taboada, another study co-author.

Few animals are naturally transparent, says biologist Richard White. Most are ocean dwellers. White has studied zebrafish, another nearly clear animal. He calls transparency “super rare.” A few fish, jellyfish, insects, and others possess the trait. In land animals, he says, transparency is “essentially unheard of outside of the glass frog.” And hiding blood while sleeping? That’s for glass frogs only.

White calls the glass frog’s disappearing act a “really amazing, dynamic form of camouflage.”

Sleep safely, little froggy. Your Creator has you covered.

In peace I will both lie down and sleep; for you alone, O Lord, make me dwell in safety. — Psalm 4:8

Why? God gives many animals remarkable ways to defend themselves, sometimes through amazing feats of camouflage. He cares for tiny glass frogs, and He cares for you!