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.

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.

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.

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.”

I should reiterate: The hydra is thought to be potentially immortal. “To say that it’s immortal implies that there might actually be hydra running around that have lived for 10,000 years,” Steele said. “I don’t know that that’s possible. But it has the potential from what we know about it for being immortal.”

The hydra’s secret seems to be that it sheds its entire body and starts from scratch every few weeks. It’s essentially just a sack of stem cells, which are kind of like blank slates. These eventually specialize into, say, a cell that makes up the tentacle. But the hydra will shed this cell after just a few days, keeping it from aging and wearing out like our own cells do. “It doesn’t have any cells that hang around long enough to get old and decrepit,” Steele said, “and therefore the individual doesn’t get old and decrepit.”

So there you have it: the secret to potential immortality. (Another miniscule creature that’s worth mentioning, the adorable eight-legged water bear, has its own method of extreme longevity: It’s not immortal, but it can dry out to just a fraction of its normal water content and live for up to 10 years as a unconscious husk, only to reanimate once it again hits water.) Why the hydra would evolve such a unique way of life is still a mystery. And if you were hoping we could apply its trick to ourselves before you yourself keel over, I have some bad news. There really couldn’t be an animal more different than ourselves, so scientists don’t hold out much hope for indulging your egomania by way of the hydra. Sorry, but it’s for your own good.

The Show Must Go On

The Hydra of Greek mythology was a vicious serpent with a bunch of heads, which would grow into two if you cut one off. The hydra of the real world can do the same, only way, way more impressively. “You can poke a hole in them and they seal it up,” Steele said. “You can cut them in half and they regenerate the missing halves. You cut them into 20 pieces and you get 20 hydra.” Its ultimate trick, though, doesn’t make a lick of sense in a world governed by, you know, certain rules and stuff.

“Dissociate” is a verb, and a very good one at that, meaning to break something down into smaller bits, such as individual cells. You do not want to be dissociated. But dissociate a bunch of hydra into a soup of cells, and incredibly they emerge again as individuals.

Hydra reproduce asexually, budding off clones, as you can see here. It’s like Multiplicity, only with less pizza.

Here’s how it works. Scientists can drop 100 or so hydra in a test tube and treat them such that they dissociate into a goopy mass of cells, then spin the tube so the mass forms into a ball. “They’re all mixed up now,” Steele said. “The cells that were on the outside of tentacles are next to cells that were on the inside of the body column. Everybody’s just mixed up, there’s no pattern to the animal at that point.”

But over the course of a few days, the cells that make up the outside of the hydra somehow make their way to the surface of the sphere, while the cells that should line the gut make their way into the center. Then the inside of the sphere forms a cavity, which will be the gut, and you end up with a hollow, two-layered sphere, just like an individual hydra has an outer layer and an inner one with fluid between the two.

Read more at Wired Science