Clearly Designed

Brian Gratwicke, CC BY 2.0, via Flickr

on January 31, 2024

The Fleischmann’s glass frog is a tiny nocturnal croaker with nearly transparent muscles and skin. Researchers have long wondered where this amphibian stashed its blood. Thanks to new research, the answer is clear.

In the forest, sunlight passes through translucent leaves, but not through most creatures sitting on those leaves. Predators hunting below can easily spot their prey’s silhouette. Hide and seek—the predator wins. But the glass frog has a trick.

When the frog is active, its blood circulates throughout its body and the red blood cells absorb light, making surrounding tissue more opaque. While napping on leaves during the day, the frog amps up its disappearing act by packing almost 90% of its red blood cells into its liver. The liver is encased in a mirrored sac to reduce the effects of visible light. Ta-da!

For most animals, cramming red blood cells together results in coagulation—the same process that forms scabs on a cut. Yet the glass frog daily removes, repacks, and restores blood cells in its circulation without suffering harm. If scientists can solve this mystery, they could improve blood clot treatments for humans.

Although escaping from predators would have been unnecessary before the fall, God ingeniously preprogrammed the genetic information essential for glass frogs to control their transparency. Hide and seek—the frog wins.

This article is from Answers magazine, October–December, 2023, p. 24.