New Species of Glass Frog Is So Transparent You Can See Its Heart

Imagine, deep in the Amazonian lowlands of the Ecuador, bright green frogs perched on the underside of tree leaves. A cacophony of tonal calls, likened to a high-pitched whistle, doesn't scare you, but beckons you to draw near them. As you get closer, you notice tiny flashes of red. You think it might be an amphibian invasion, until it's crystal clear that it's just a matter of the heart: The frogs have a transparent underside, revealing their beating hearts.

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Based on morphology, the frog's vocalizations and DNA analysis, researchers have identified a new species of glass frogs called Hyalinobatrachium yaku — news that will surely make some herpetologists green with envy. The findings were published in the journal ZooKeys. Belly-side up, H. yaku's kidneys, urinary bladder and heart can be seen clearly, like an X-ray. But you might have to squint to see the frog's heartbeat, since the average frog is only 0.8 inches (2 centimeters) long.