Absurd Creature of the Week: This Amazing Little Critter Just Might Be Immortal

The hydra is one of the few creatures on Earth that looks exactly like a palm tree, another being the dancing palm tree during Katy Perry’s Super Bowl halftime show. But let’s not speak of the dancing palm tree. © Visuals Unlimited/Corbis

Listen, I don’t want to live forever. First of all, it’d take a really long time to work enough to save up for that long of a retirement. And I dunno, I’m a writer. I live by deadlines. And there ain’t no bigger deadline than your own inevitable death.

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But there’s one creature that doesn’t need to get hung up on retirement or deadlines, and accordingly it could well be immortal. This is the bizarre existence of the hydra, a half-inch tube of jelly that inhabits fresh water all over the world, where it lives a long, long time under the right conditions—and if you don’t assault it.

Yet even then, it has remarkable powers of regeneration. Cut it in half and you’ll eventually end up with two hydra. Mix a bunch of them up in a test tube, break them all apart into single cells, and still they’ll re-form into a ball and split off as individuals. Yeah, I know, that doesn’t really seem possible. But stick with me here.

As Kermit once said, it’s not easy being green. These transgenic hydra, which are loaded with a green florescent protein, would no doubt confirm that if they too had a puppeteer making them say stuff. Rob Steele

Who Wants to Live Forever

This is a supremely simple animal, belonging to the same group as jellyfish, the cnidarians. “I sometimes describe hydras sort of like a little free-living piece of intestine,” said hydrobiologist Rob Steele of the University of California, Irvine. At one end is a sticky disk, which the hydra uses to anchor itself, and at the other is a mouth and tentacles packed with stinging cells, which fire toxic harpoons into prey. Holding the quarry in place, the hydra then ratchets its mouth over the victim—typically a tiny crustacean called a water flea—until it’s entirely enveloped.

Back in the ‘90s, a fella named Daniel Martinez gathered up 60 of these creatures and isolated them in their own tiny tanks. Hydra reproduce asexually, budding off little clones, so Martinez had to pick those young out and toss them. After four years of this, not only were the hydra still alive, but they looked good as new. Four years may not sound like a long time, but the rule in nature is that the smaller you are, the shorter you live. Thus can small insects last only a matter of weeks, while blue whales keep ticking for nearly a century. Something the size of a hydra living for four years is just ridiculous.

So Martinez published his findings, declaring the hydra potentially immortal. Unsurprisingly, this rustled a few people’s jimmies. “So he published that result,” Steele said, “and then the naysayers came along and said, ‘Well maybe the average lifespan of hydra is six years, so you didn’t do the experiment long enough.’ So he went back and restarted the experiment, and I think he’s now at about year eight,” making his hydras the oldest known specimens. “He’s going to do it for 10 years, and then he says never again. If 10 years isn’t enough for them, that’s their problem.”