Turritopsis nutricula is a small hydrozoan that once reaching adulthood, can transfer its cells back to childhood. This adaptive trait likely evolved in order to extend the life of the individual. Several different species of the genus Turritopsis were formerly classified as T. nutricula, including the "immortal jellyfish" which is now classified as T. dohrnii. Wikipedia, Turritopsis nutricula
See Also
Bearden - Precursor Engineering: Via Tickling of the Dirac Sea Vacuum