Jellyfish

The impossible claim This animal can revert to its juvenile polyp stage when injured, starving, or aging — restarting its entire life cycle, potentially indefinitely. The verified facts Turritopsis dohrnii, the “immortal jellyfish,” is a small (~4.5 mm) hydrozoan. When environmental stress or old age threatens it, it performs transdifferentiation: its adult medusa cells transform directly into polyp cells, collapsing the bell into a cyst that regrows into a new polyp colony. Genetically, it’s the same individual — biologically, it’s a baby again. ...