This fish can survive a year sealed in dry mud. Its pool is drying up around it, and it isn't leaving.
It's an African lungfish. It has gills, but they're too weak to keep it alive. It has to swim up and gulp air. Cut it off from the air, and it suffocates.
So when the dry season takes the water, it digs into the mud and curls up. Its skin pours out slime. The slime dries into a thin, papery bag with one opening at the mouth. That's how it breathes.
Then it waits. Its heart beats half as fast. It stops eating and burns its own muscle for fuel. Scientists kept one sealed in mud for 410 days. When the rain comes back, the mud goes soft, the bag splits open, and the fish swims out.
The trick is ancient. Lungfish have been around for more than 400 million years, since before the first trees. Their burrows have been found turned to stone, with the fish still inside.
They came through the worst mass extinction in Earth's history, and they outlived the dinosaurs. Every time the world dried out, this family of fish just waited in the mud for rain.
