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I don’t know if you’ve noticed, but animals kind of need oxygen.
I don’t know if you’ve noticed, but animals kind of need oxygen.

That’s because animals generally get their energy from cellular structures called mitochondria,
That’s because animals generally get their energy from cellular structures called mitochondria,

and those processes require oxygen to work.
and those processes require oxygen to work.

So if somebody stole all of the Earth’s O2, things would end pretty quickly around here.
So if somebody stole all of the Earth’s O2, things would end pretty quickly around here.

Except, as it turns out, there are at least some animals that would be perfectly fine.
Except, as it turns out, there are at least some animals that would be perfectly fine.

Because in 2010, scientists published a paper announcing
Because in 2010, scientists published a paper announcing

that they’d found three species of them that straight-up don’t need oxygen!
that they’d found three species of them that straight-up don’t need oxygen!

Now, to be clear, not all life needs oxygen.
Now, to be clear, not all life needs oxygen.

There are plenty of single-celled microbes that are anaerobic,
There are plenty of single-celled microbes that are anaerobic,

meaning they can survive just fine without the stuff.
meaning they can survive just fine without the stuff.

Instead of oxygen, these organisms can use other molecules like sulfate or nitrate.
Instead of oxygen, these organisms can use other molecules like sulfate or nitrate.

But for years, scientists thought a system like that wouldn’t work for animals,
But for years, scientists thought a system like that wouldn’t work for animals,

since their complex, multicellular bodies have higher energy requirements.
since their complex, multicellular bodies have higher energy requirements.

Instead, they thought animals needed the more efficient energy production that takes place in mitochondria.
Instead, they thought animals needed the more efficient energy production that takes place in mitochondria.

And then came that 2010 paper.
And then came that 2010 paper.

This discovery happened in the L’Atalante basin,
This discovery happened in the L’Atalante basin,

three thousand meters below the surface of the Mediterranean Sea.
three thousand meters below the surface of the Mediterranean Sea.

L’Atalante is a deep hypersaline anoxic basin,
L’Atalante is a deep hypersaline anoxic basin,

meaning it’s super salty and completely devoid of oxygen.
meaning it’s super salty and completely devoid of oxygen.

It’s the kind of place you wouldn’t expect to find animals.
It’s the kind of place you wouldn’t expect to find animals.

And indeed, when a research team visited three times between 1998 and 2008,
And indeed, when a research team visited three times between 1998 and 2008,

that’s generally what they saw.
that’s generally what they saw.

They did find a lot of single-celled organisms living in the basin,
They did find a lot of single-celled organisms living in the basin,

but most of the animals they saw were dead,
but most of the animals they saw were dead,

the result of a so-called “rain of cadavers” from oxygenated waters above.
the result of a so-called “rain of cadavers” from oxygenated waters above.

Most of the animals, but not all of them.
Most of the animals, but not all of them.

Because the team also found an unusually high abundance of tiny, sediment-dwelling animals
Because the team also found an unusually high abundance of tiny, sediment-dwelling animals

called loriciferans, and they were seemingly very alive.
called loriciferans, and they were seemingly very alive.

Loriciferans are pretty weird creatures to begin with.
Loriciferans are pretty weird creatures to begin with.

Their heads are covered in spines, and their bodies are typically encased in a vase-like shell called a lorica.
Their heads are covered in spines, and their bodies are typically encased in a vase-like shell called a lorica.

But finding them in an oxygen-free basin was a whole new level of weird.
But finding them in an oxygen-free basin was a whole new level of weird.

The researchers observed that the loriciferans were still taking up nutrients,
The researchers observed that the loriciferans were still taking up nutrients,

and that some had recently molted.
and that some had recently molted.

Some even had developing offspring inside them.
Some even had developing offspring inside them.

So these animals apparently spend their lives buried in this sediment, with no oxygen,
So these animals apparently spend their lives buried in this sediment, with no oxygen,

not only surviving, but thriving.
not only surviving, but thriving.

Part of this incredible survival might be down to their size.
Part of this incredible survival might be down to their size.

At less than one millimeter long, loriciferans have pretty low energy needs.
At less than one millimeter long, loriciferans have pretty low energy needs.

But they also seem to have some unique adaptations.
But they also seem to have some unique adaptations.

For one thing, they don’t have mitochondria!
For one thing, they don’t have mitochondria!

Instead, they have cellular structures that look a lot like hydrogenosomes.
Instead, they have cellular structures that look a lot like hydrogenosomes.

These are organelles that some microbes use to produce energy,
These are organelles that some microbes use to produce energy,

and they use hydrogen ions in place of oxygen.
and they use hydrogen ions in place of oxygen.

Alongside these structures, the researchers also noticed shapes that might be microbes
Alongside these structures, the researchers also noticed shapes that might be microbes

living inside the loriciferans’ cells.
living inside the loriciferans’ cells.

That’s intriguing because some anaerobic, single-celled organisms also have symbiotic microbes
That’s intriguing because some anaerobic, single-celled organisms also have symbiotic microbes

that live alongside their hydrogenosomes.
that live alongside their hydrogenosomes.

All in all, it looks like these loriciferans have developed similar cellular structures
All in all, it looks like these loriciferans have developed similar cellular structures

to anaerobic microbes for living in the same way,
to anaerobic microbes for living in the same way,

although it’s not clear how they did this.
although it’s not clear how they did this.

One option is that they retained these adaptations from an earlier ancestor
One option is that they retained these adaptations from an earlier ancestor

more similar to anaerobic microbes.
more similar to anaerobic microbes.

But it’s also possible that their ancestors swiped genes from their microbial neighbors,
But it’s also possible that their ancestors swiped genes from their microbial neighbors,

allowing them to use the same cellular tricks for survival.
allowing them to use the same cellular tricks for survival.

Of course, this is an extraordinary claim, and some researchers have doubts.
Of course, this is an extraordinary claim, and some researchers have doubts.

For example, a study published in 2015 looked in the same basin
For example, a study published in 2015 looked in the same basin

and was unable to find independent evidence of living loriciferans.
and was unable to find independent evidence of living loriciferans.

The researchers of the original study are still confident in their results,
The researchers of the original study are still confident in their results,

but it may take more confirmation to convince everyone.
but it may take more confirmation to convince everyone.

If these results do hold up, though,
If these results do hold up, though,

it could change how we understand the requirements of complex life.
it could change how we understand the requirements of complex life.

It would have implications for the diversity of animal life in the world today,
It would have implications for the diversity of animal life in the world today,

for scientists interested in how life got started on an oxygen-deficient early Earth,
for scientists interested in how life got started on an oxygen-deficient early Earth,

and maybe even for scientists looking for life elsewhere in the solar system.
and maybe even for scientists looking for life elsewhere in the solar system.

Ultimately, life is so adaptable and endlessly diverse,
Ultimately, life is so adaptable and endlessly diverse,

that we wouldn’t be surprised if there are more surprises to be found.
that we wouldn’t be surprised if there are more surprises to be found.

Critical thinking in science is obviously a great thing, though,
Critical thinking in science is obviously a great thing, though,

and that’s why it’s so important for researchers to check each other’s work.
and that’s why it’s so important for researchers to check each other’s work.

And if you want to brush up on your critical thinking skills, or just learn some really cool stuff,
And if you want to brush up on your critical thinking skills, or just learn some really cool stuff,

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the Daily Challenges from Brilliant are a great way to do that.

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