In most instances, Turritopsis reproduce like all species: the meeting of free-floating eggs and sperm. And for the most part, they die like all species. However, according to Maria Pia Miglietta, a researcher at Pennsylvania State University and author of a new study, in cases of starvation, physical damage or another crisis, "Instead of sure death, Turritopsis transforms all of its existing cells into a younger state," she says.

Through this process - called transdifferentiation - the jellyfish is able to return to its polyp state, the first stage of the life of a jellyfish. During transdifferentiation, its cells can become completely transformed. For example, a muscle cell could become a nerve cell - even an egg. The jellyfish then reproduces asexually and breed hundreds of jellyfish that are identical to the original adult. This process can be repeated - again and again, but only as an emergency measure. As Dr Maria Miglietta of the Smithsonian Tropical Marine Institute says, "We are looking at a worldwide silent invasion."

This tiny creature, the size of a human pinky nail when fully developed, was first discovered in 1883. However, it wasn't until the 1990s that this unique ability to transform back into younger self once it has become sexually mature and has mated was uncovered. Many marine biologists and geneticists are now studying the jellyfish in order to determine how it is able to reverse its aging process.

News Release: Immortal jellyfish swarm world's oceans National Geographic News January 29, 2009