The 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. 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.

Researchers have identified a new species of glass frogs called Hyalinobatrachium yaku. 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.

H. yaku, which ranges in color from apple-green to yellowish-green, also displays behaviors atypical for glass frogs. Males take the lead on babysitting their egg clutches, rather than females. And although some of the populations the team studied clung to the underside of leaves over streams, as usual for glass frogs, some of the H. yaku perched on shrubs, ferns and grasses several inches above the ground and more than 30 meters (98 feet) away from the closest stream.

The new species also lacks vomerine teeth, has a shorter snout than usual, has a tympanic membrane (almost like a human eardrum) that blends in with its surrounding skin, and has a bulging liver, among other distinguishing characteristics.


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