### Immortal Jellyfish
Turritopsis dohrnii
When this tiny jellyfish gets old or injured, it hits reverse and turns back into a baby.
The Story
Meet Turritopsis dohrnii, the immortal jellyfish. If a superhero responded to a fatal injury by shrinking into an infant to start life over, you'd call it incredibly weird—which is why this creature earns a maximum Weirdness score. But don't confuse biological immortality with invincibility. With a raw physical attack Power of absolute zero and near-nonexistent Defense, it cannot fight off predators like sea turtles.
Instead, it survives by hitting the rewind button. The jaw-dropping moment happens when the adult jellyfish—no bigger than your pinky nail at just 3 to 4.5 millimeters across—decides it’s time to bail out of adulthood. It absorbs its 80 to 90 tentacles, shrinks into a shapeless blob, and sinks to the ocean floor. From that blob, it transforms back into a baby polyp colony, ready to birth brand-new adults!
How It Works
- The Biological Reset Button: Most animal cells have a permanent job. Once a human cell becomes a nerve cell, it stays that way. The immortal jellyfish uses a biological loophole called transdifferentiation. - Shapeshifting Cells: During transdifferentiation, mature, specialized cells in the jellyfish's body completely lose their old identities. They alter their state and transform into completely different types of cells, rebuilding the animal from scratch. - Cloning a Comeback: Once it reverts to a plant-like baby polyp colony on the ocean floor, it doesn't just grow back into one jellyfish. The colony buds off to produce multiple, genetically identical adult medusas (which start out with only 8 tentacles before growing to 80 or 90).
