Turritopsis dohrnii, the
immortal jellyfish, is a species of small,
biologically immortal jellyfish found in the
Mediterranean Sea and in the waters of
Japan. It is one of the known cases of
animals capable of reverting completely to a sexually immature, colonial stage after having reached sexual maturity as a solitary individual, others include also the jellyfish
Laodicea undulata and
Aurelia sp.1.