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.
- Reversion can repeat without a known limit; no senescence has been observed
- The process was discovered accidentally in the 1980s (medusae kept in jars kept “re-juvenating” instead of dying)
- It spreads worldwide by hitchhiking in ship ballast water
Watch
🎬 See the Short on YouTube — Episode 5, “This Animal Never Dies of Old Age.”
Sources
- Miglietta, M. P. & Lessios, H. A. (2009). A silent invasion. Biological Invasions.
- Schmid, V. (2005). Transdifferentiation in medusae. International Journal of Developmental Biology.
- Piraino, S. et al. (1996). Reversing the life cycle. Biological Bulletin.
Part of Impossible Creatures — every fact verified, every creature real. Watch the Shorts at youtube.com/@taginbertcom.