Adaptation & Survival

The Axolotl can regrow its legs, heart, spine, eyes and even parts of its brain.

Why it works: When an axolotl loses a leg, nearby cells return to a simpler, baby-like state and form a special blob called a blastema. These cells remember which part of the leg was lost, so they rebuild only the missing piece. A signal chemical called retinoic acid acts like a position marker that helps cells know how far up the limb they are, so they build the right segments. Very little scar forms, which lets the new limb grow back cleanly. The axolotl also stays in its baby form for life because its body makes very little of the 'grow-up' thyroid hormone.

The Immortal Jellyfish can avoid dying of old age by folding back into a baby and growing up again.

Why it works: When this jellyfish is hurt, starving, or just getting old, its grown-up body cells don't keep dying. Instead they actually change into different kinds of cells, a switch scientists call transdifferentiation. Using that trick, the whole jellyfish collapses into a little blob and rebuilds itself as a polyp, the baby stage stuck to the seafloor, which then grows brand-new jellyfish. Because its cells can keep re-switching, there's no known limit to how many times it can restart, though it can still be eaten or get sick and die.

The Sea Cucumber shoots its own sticky internal organs out of its rear at attackers.

Why it works: The sea cucumber doesn't really fire its guts on purpose like a cannon — it uses water pressure. Many sea cucumbers store sticky threads called Cuvierian tubules inside their body, attached near their breathing parts. When a predator attacks, the animal squeezes its muscles hard, water rushes into the threads, and they shoot out the rear and stretch up to 20 times longer, getting sticky in seconds. The threads also hold a natural poison (a chemical called holothurin), so a tangled-up crab or fish gets a nasty, gluey surprise while the sea cucumber escapes and slowly regrows the parts it lost.

The Tardigrade survived the raw vacuum of space, completely unprotected.

Why it works: The tardigrade's secret is drying out on purpose. When its water disappears, it pulls in its head and legs and curls into a ball called a "tun," pushing out almost all of its water so its body chemistry nearly stops. To keep its squished cells and DNA from breaking while dry, it makes special protective molecules (including proteins scientists call CAHS, which turn the inside of the cell into a glass-like solid, and one nicknamed Dsup that shields its DNA). With its body switched off and protected this way, there is almost nothing left for cold, heat, radiation, or empty space to damage until water returns and wakes it up. Scientists are still working out exactly how all these tricks work together.

The Wood Frog can freeze into a solid lump of ice every winter and thaw back to life in spring.

Why it works: When ice starts touching a wood frog's skin, its liver gets a signal and quickly turns its stored sugar (glycogen) into lots of glucose, pumping this sugary 'antifreeze' into the blood and all its cells. The trick is WHERE the ice forms: water gets pulled out of the cells and freezes in the spaces between them, so the delicate insides of cells stay liquid. The glucose keeps too much water from leaving each cell, stops the cells from shrinking too far, and blocks sharp ice from forming inside them. With its blood frozen in place the heart has nothing to pump, so it simply stops until spring thaws everything out.