Bryan Johnson· Author
The freshwater hydra constantly regenerates its own cells and doesn’t succumb to senescence. It is effectively ageless. The "immortal jellyfish" (Turritopsis dohrnii) can revert its cells back to a youthful state and restart its life cycle indefinitely. Lobsters produce an especially active form of an enzyme called telomerase that preserves their telomeres and keeps their DNA from degrading as they age.