Glass Frog
Weirdness 9/10

The frog with see-through skin you can watch its heart beat through

This frog has see-through skin — you can literally watch its heart beat through its body.

The short version

The glass frog has a translucent belly, so you can see its heart, liver, and intestines working inside. The transparency blurs its outline against a leaf so predators below can't spot it, and when it sleeps it hides almost all its red blood in its liver to become even more invisible.

Why it's so weird

  • The Glass Frog has see-through skin, so you can watch its heart beat through its body.
  • The Glass Frog hides almost all of its red blood inside its liver while it sleeps to turn even more invisible.
  • The Glass Frog has a translucent belly that reveals its heart, liver, stomach, and intestines working inside.
  • The Glass Frog blurs its outline against a bright green leaf because light passes straight through its body, so predators below can't spot it.
  • The Glass Frog is now inspiring medical research into preventing dangerous blood clots in people.

The full story

This frog has see-through skin — you can literally watch its heart beat through its body. Meet the glass frog, one of the strangest animals in the entire rainforest. Flip it over and its belly is almost completely transparent. You can see its heart pumping, its liver, its stomach, even its intestines, all quietly working away inside. But the transparency is not just for show. Sitting on a bright green leaf, light passes straight through its body and blurs its outline, so predators looking up from below simply cannot spot it. And here is the really wild part. When a glass frog falls asleep, it hides almost all of its red blood inside its liver, turning itself even more invisible, then pumps it back out when it wakes. Scientists are now studying that trick to help prevent dangerous blood clots in people. Follow for more weird animal facts.

Watch the 45-second version

Glass Frog gallery

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