The immortal Hydra

As young children we learn a hard truth. In the end all animals die… or do they? Next up we have the story of an ongoing science experiment and a freshwater animal that just may have found the fountain of youth.


As young children, we learn a hard truth.

In the end, all animals die -- or do they?

Next up, we have the story of an ongoing science experiment and a freshwater animal that just may have found the fountain of youth.


One day 250 years ago, a young teacher named Abraham Trembley was walking through a field, and he came to a pond, looked in, and there in the water he saw this thing.

It was very little with wavy tentacles on top and a tubelike body, and just to see what would happen, he cut it in half.

Much to his surprise, instead of dying on the spot, the animal grew back into two full-sized adults.


So he did it again.

The same thing happened.

And again.

This animal just wouldn't die.

The hydra -- that's what it's called -- has extraordinary powers of regeneration, almost as if it's built not to die ever, which is ridiculous 'cause everything dies, we assume.

In science, however, you don't assume, you check.

So, in the 1990s, a curious young scientist, Daniel Martinez, having heard that hydras go on and on and on, decided to do an experiment.

He gathered a bunch of hydra from a pond in Long Island, New York, put them in some tanks where he could keep an eye on them, and he thought, 'I'm gonna wait until I see them die naturally,' and hydra do die.

You take them out of water, they'll shrivel up.

But in a natural environment, nobody knows.

So, Daniel waited.

First his hydras had babies.

Then a week passed, then months passed.

Meanwhile, Daniel's school year ended.

He got a job out west in California.

Rather than miss the death of his hydras, he put them in a cooler, traveled cross-country with his brother, and every day wherever he was, he fed them, washed them, and he waited.

A year passed.

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Then two years, three years.

Still no deaths.

Four years out, Daniel published a science paper that said hydras apparently never die.

Well, what he really said was, 'Mortality Patterns Suggest Lack of Senescence In Hydra.'

Now, you think four years is kind of a short-term for a claim like this.

I mean, a lot of us are past our fourth birthdays, and we still expect to die, but here's the thing.

There's a well-known pattern in nature.

The sooner you have babies, the sooner you die.

If you're a tiny fly, you have your babies quickly, after a couple of weeks, and you die, Mm, here after a couple of months.

If you're a huge elephant, you wait 13 years to have your babies, you live for another 40 or 50 years, and then you die right around here.

And this is true across the animal kingdom except when it comes to hydra.

Remember, hydra have their babies after a couple of days, so they should die after, say, a month, but Dan's hydra had lived for four years when he published his paper, and they are still going strong today.

They've now lived for more than eight years.

That is 100 times their expected life span.

That's like an elephant living for 5,000 years.

It's like everybody else got the memo that in the end, you die, but not the hydra.

So what's going on?

Daniel says, 'Here's my theory.

Most animals, humans and hydras both, begin with a cell, a single cell, and they multiply.

In humans, our cells multiply a lot, then specialize, age, break down, and eventually they wear out, and so we die.

In a hydra, the cells, 'A,' don't specialize much.

Most hydra cells are embryonic cells, and embryonic cells, like embryos, they're simple and great at staying young.

So you can watch them here moving up the tentacles, moving down to the foot, and before they have a chance to get much older, they flake off to be replaced, as you see here, by newer cells.

Over four years, the hydra replaces all its cells, its entire body, over 60 times.

Every cell in the body is completely new every 20 days.

It even looks like a fountain of youth.

So, for all intents and purposes,' Daniel says, 'these animals are' -- and I want to use his word -- 'immortal.'

Joining me now is Adam Cole, the creator and host of NPR Science YouTube Channel, Skunk Bear.

So how is it possible that these hydra can keep doing this?

It's all about simplicity for them.

They don't have to create a lot of the specific organs or body systems that we do, and that means their cells can be very simple and just constantly replenished.

Where are they usually found?

There's all different subspecies or species of hydra, and they're found just in freshwater ecosystems all over the world.

Has there been any controversy over the findings that Martinez had?

Um, I think there's a lot of people who have called him and said, 'How can we make this into a facial cream?,' or sort of these rejuvenating treatments, and I don't think he has much interest in that area.

And does hydra have a natural predator or no?

I'm sure there's things that eat it.

It's just one of those little squishy things that runs around.

I'm sure there's -- You know, whatever's up the food chain one rung is definitely eating them.

Are they unique in this, or are there any other...?

There are some others.

There's little planarian worms, these tiny worms that people believe have a similar ability.

There's a jellyfish, tiny, little jellyfish that people think, also, never dies.

The thing they have in common is they're all very simple and all very small.

This makes me think of the -- Was it the 'Agents of S.H.I.E.L.D.,' the Marvel, and always fighting Hydra -- cut off one head, another one springs up?


That's sort of -- I mean, the legend of the Hydra is what gave name to that fictional organization and this animal.

All right.

Adam Cole from NPR's Skunk Bear.

Thanks so much for joining us.

Thank you.

Learn more about the biologically immortal hydra on our website,