“Turritopsis nutricula is a hydrozoan with a life cycle in which it reverts to the polyp stage after becoming sexually mature. It is the only known case of a metazoan capable of reverting completely to a sexually immature, colonial stage after having reached sexual maturity as a solitary stage. It does this through the cell development process of transdifferentiation. Theoretically, this cycle can repeat indefinitely, rendering it effectively immortal.”  – Wiki Blurb

[via ZME Science]