What we all feared: jellyfish are immortal

A species of jellyfish, Turritopsis nutricula, may be the world's only known immortal species, according to scientists. Apparently the hydrozoan can vacillate between youth (polyp) and adult stages of growth--prolonging it's unusual, eldritch existence. From  WorldHealth.net:

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."

Upside: they're the size of a human pinky fingernail
Downside: THEY'RE IMMORTAL!!

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