No. 5: What’s the World’s Only Immortal Animal?

Sorry, Team Edward: The world’s only immortal animal doesn’t have pale marble skin, artfully disheveled bronze hair, or topaz eyes that pierce your soul. The world’s sole immortal animal is downright unsexy.

Meet the Turritopsis dohrnii, a jellyfish that scientists in 2009 declared “the only immortal animal” in the world. The round, slightly opaque bulbous body of the jellyfish is accented with floppy, thin tentacles — not exactly the image of a sexy beast.

How could this be? And how do you prove immortality anyhow? The Turritopsis dohrnii turns back time by reverting to its first stages of life in a process called transdifferentiation. Just as a salamander might regenerate its limbs, this jellyfish, native to the Caribbean, can regenerate its cells over and over again. Instead of dying, the Turritopsis dohrniitransforms all of its existing cells into a younger state,” says Maria Pia Miglietta, who led the study at the Smithsonian Tropical Marine Institute in Panama.

Miglietta, who is now a researcher at Pennsylvania State University, said that “studying Turritopsis and its life cycle can bring a great contribution to science.” Her study drew a huge spike of interest not only among Web surfers but also from media, the scientific community, and students, she says.

The jellyfish is scientifically fascinating but doesn’t quite measure up to the immortal beings in literature and film. Plus, Turritopsis dohrnii provokes a slew of compelling, philosophically tinged questions: Does self-regeneration really count as immortality? Or is this jellyfish really an example of the living undead?

As any respectable horror fan can tell you, there’s a world of difference between undead and immortal. Steve Mockus, the author of “How to Speak Zombie” and editor of the forthcoming “Worst-Case Scenario Survival Handbook: Paranormal,” can attest to this. “Both zombies and vampires are undead, but zombies aren’t immortal, because they keep decaying,” he explains. Besides, zombies don’t get nourishment from chowing down on humans, as vampires do.

“Neither one is ‘alive,’ but one of them eventually expires,” Mockus says. “So a zombie dog wouldn’t be immortal. But a vampire dog, now you’re talking.” As for the possibility of immortal vampire jellyfish, well, luckily for us, jellyfish have no teeth.

–Eugenia Chien

Before joining Yahoo! as a Search editor, Eugenia Chien was a reporter at New America Media in San Francisco. Her work has appeared in the San Francisco Chronicle, on KQED, and on KALW. She crushes on geek heroes, transit enthusiasts, and animal lovers.