Image from incrediblebeings.com

The jellyfish pictured above, Turritopsis nutricula, is biologically immortal. Turritopsis nutricula is able to survive indefinitely by reverting to its polyp (juvenile) form after reaching sexual maturity and procreating. Turritopsis nutricola does this through the process of cell transdifferentiation, the conversion of one type of cell into another. The mature jellyfish (medusa form) can change its cells into stolons and later into polyps.

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