Hi, Benjamin here.
Welcome to the Nature Briefing podcast, the Friday show where we talk about a couple of stories we've read about in the Nature Briefing, which is, of course, Nature's daily email roundup of the latest science stories.
And joining me today to chat is none other than Sharmini Bundel.
Sharmini, thank you for being here.
I am actually really excited about today's story.
Why don't we start with you then, in that case.
Tell me what you've got.
Look, I'll give you the preview.
It's got mitochondria.
We all love mitochondria.
Ding.
It's got parasites.
Ding, ding.
It's got evolution.
I love evolution.
Ding, ding, ding, ding, ding.
This is a preprint from BioRxiv, so not a peer-reviewed paper, but I read an article in Nature where they've covered it.
And yes, it's about mitochondria, the powerhouse of the cell, little organelles found in eukaryotic cells producing energy, and it's kind of about how our cells got to be, how they are right, but it came from an experiment with a parasite Okay,
Parasite biology, often very strange.
Tell me what's going on here.
So a group of researchers infected human cancer cells with a parasite called Toxoplasma gondii.
This is the parasite that causes toxoplasmosis which, if you've ever gotten pregnant, they tell you to stay away from cat poo, so you don't get toxoplasmosis.
But it's actually a really common parasite.
And it's also here's a little side tour it's the one that changes the behaviour of rodents to make them more likely to get eaten by cats.
They stop being scared.
Yeah.
That's a whole other story, but go look it up.
It's great.
Mind-controlling parasite.
So anyway, these researchers are there infecting these human cancer cells with some toxoplasma.
And what happened was that these little parasites in the cell started having an effect on the mitochondria in the cell.
These membrane-bound organelles.
And these mitochondria started to shed their outer membranes.
And that membrane then formed its own little bubbly structure.
They call them spots.
Structure's positive for outer mitochondrial membrane.
Spots.
Oh, yeah.
And those little spots went and engulfed some other little organelles, little things in the cells called lysosomes, which do sort of waste disposal jobs in the cell.
And it turns out that this weird change was actually helpful to the parasite.
When they stopped this from happening, the parasite didn't do as well.
So something about this process that's triggered by the parasite is benefiting the parasite.
So let me get this straight.
So parasite infects cells.
Yes.
Something that you would expect is a defence mechanism isn't.
So the mitochondria loses its membrane.
That joins with another organelle.
But instead of...
Defeating a parasite, this helps the parasite.
Yeah, you make an interesting point because quite possibly this kind of reaction from the mitochondria, this ability to shed some of their membranes and form new organelles, that could well be usually a benefit.
That could be an adaptation, to maybe help the cell adapt to different stresses by creating new structures.
That is possible.
But yes, certainly in this one specific case, which is a very narrow thing that they were looking at this one particular situation.
But yeah, in this situation, the Toxoplasma gondii is definitely doing well from this and The implication here is that this is an adaptation by this parasite to benefit it by manipulating these mitochondria.
And also you mentioned that this is a new organelle and that's super interesting too.
Well, so here is where it gets... much broader.
We're gonna step away from infecting cancer cells with a specific parasite and we're gonna start asking questions about how our cells evolved.
So you might know that the prevailing theory is that back in the mists of time there were two different types of cell.
And one of the bigger types absorbed one of the little smaller bacterial types and, instead of eating it, dissolving it, consuming it, kept it around.
And that is the origin.
We think of what's called eukaryotic cells, the complex cells in animals and plants that have organelles in.
So the idea is we got organelles by... essentially eating a bacteria and keeping it.
Mitochondria have their own little DNA in them, and it's not the same as the nuclear DNA.
It's kind of like bacterial DNA.
Right.
So mitochondria are thought to originally have been a bacterial cell, our prokaryote.
But other organelles then, are they thought to have come from somewhere else as well?
Well, there's a kind of big gap in our understanding of eukaryotic cells because there's loads of differences between us and the ancestors.
That would have been maybe absorbing little bacteria and turning them into mitochondria.
You know, we have nuclear membrane, we have other organelles as well.
And I don't think it's super clear where they all came from.
But this observation that the mitochondria can in some circumstances shed some outer membrane and kind of make new organelles, that's really fascinating because that could be a possible route for making other organelles.
This is a very new idea, but the suggestion here is that it could well be that other organelles came from mitochondria, that them shedding their membranes made some of the other organelles we find in our cells.
Oh, so that's the evolution aspect that you mentioned then.
Obviously, it's hard to know exactly what went on.
What happens now?
This is an unusual finding.
Like, where do researchers take it?
Yeah, and it supports a particular theory, ideas that have been shared about how eukaryotic cells and their organelles might have developed.
It's one little clue.
It maybe backs up an older paper that people were really sceptical of.
That maybe suggested the same thing, but now they might go and re-look at that and think, oh yeah, maybe there was something in that and maybe spur some new avenues of investigation.
But I just think it's really interesting that such a niche look at the behaviour of this strange little parasite could give us this potential clue to this grand evolutionary question.
Well, that is a fascinating one and a strange finding that potentially opens up some broader questions.
But let's move on to our second story today that also, I guess, opens up some questions.
But I think we need to hop into our absolutely real time machine for this.
We need to head back to the late Cretaceous period, like from about 100 to about 70 million years ago.
I'd love a bit of late Cretaceous, yeah.
Well, we're going to meet an extinct creature that was potentially absolutely enormous and a top underwater predator.
Now, this is a story that I read in Nature and it's based on a paper in Science.
Oh, underwater.
I was going to say, oh, is it dinosaurs?
I love dinosaurs, but underwater.
So I guess not.
There were some marine reptiles swimming around, I reckon, Cretaceous times.
Mosasaurs, ichthyosaurs, maybe.
Is that where we're going with this?
Absolutely.
Absolutely right.
That is the right sort of time.
So Mosasaurs, yes, giant aquatic reptiles, like 12 metres long.
It's about 40 feet long.
Plesiosaurs, I know you and I have spoken about Plesiosaurs with their long necks many times.
Little hens, yeah.
And that's in the ocean.
And on land, of course, we've got T-Rex at that sort of time.
So this was a period of giant vertebrates, right?
These are big, old animals.
And it's often thought that invertebrates were kind of like, basically dinner animals, essentially for the other animals, quite small things.
But there may have been an animal that outstripped all these vertebrates.
It was an invertebrate, an octopus in fact, and an absolutely gargantuan one.
But octopuses, I mean octopuses, can grow quite big today, but we're not talking shark size.
Well, maybe we are.
So let me give you some facts.
So you're right.
Cephalopods, more generally, so that includes octopuses, can get quite big, right?
The giant squid can be like 10 metres long.
But this octopus is thought to be...
Well, about the length of a tennis court.
So 19 metres long, like 60 feet long.
So it would have potentially massively outstripped the Mosasaurs and things like that.
Now, these animals have been identified from chitinous jaw fossils, right?
So octopuses have got kind of a beak that's made out of chitin and it's the only bit that survives the fossilization process period really, because soft-bodied animals don't preserve very well.
It's very unusual to find a soft-bodied animal, so not much has been known about the size of these octopuses and their lifestyle and so forth, and that's what this new work has tried to maybe open the door on a little bit.
So are they essentially just guessing from the beaks?
Because the beak is all we have.
Everything else is an extrapolation.
Pretty much.
That's exactly right.
So the team reanalyzed 15 large fossil octopus jaws.
And they found 12 new fossils as well by looking at some carbonate rocks.
And they worked with AI here to try and find these things.
And they divided these animals into two species.
Now, apparently, these belong to the same evolutionary group as modern Dumbo octopuses.
You know these ones that have the little ears?
Then they flap along and they live quite deep.
That's right.
They're actually fins to help them swim through the water.
Anyway, on the basis of the anatomy of modern octopuses, right, they've had to do some comparisons.
They reckon that one of the species Nanomatethys haggartii or haggartii I hope I'm pronouncing that correctly could have been say, 19 metres long potentially.
Although a lot of that would have been its head arms right, the head part would potentially only have been a mere four meters long, only four meters right yeah, i'm imagining that i feel like this is ripe territory for a horror movie of some kind, with a terrifying giant cretaceous octopus in.
Yeah well, of course, the kraken, that mythological cephalopod that terrified sailors for centuries.
Right, that was potentially based on giant squids which, as i say, about 10 meters long.
This one is twice as long as that, but not everyone, i have to say, is convinced.
A lot of this work, as we've said, is based on extrapolating and looking at modern octopus species, And there is a lot of variability in modern octopuses between the sort of head bit, I suppose, and the arm length right.
Some folk are saying that maybe this octopus would have been at the lower end of the team's estimates, putting it around just six and a half metres long.
Pretty small.
It's kind of hard to know, but the team have also made some other inferences as well about the lives of these massive creatures.
Did they eat mosasaurs for breakfast?
Maybe not mosasaurs, but these beaks were pretty chipped and they showed signs of wear.
Now the biggest one of these animals.
They reckon that maybe 10 of the jaw had been worn down, maybe by crushing things like crustaceans and you know bivalves, smaller hard prey which could chip this.
And the authors reckon that the pattern of wear suggests that these animals were essentially apex predators in the ocean during the Cretaceous period.
And what's kind of weird is that there's an asymmetric wear pattern.
So one side was maybe more worn down than the other.
And the authors reckon that this shows that these animals had a preference for kind of how they looked, they ate, which suggests that maybe they were capable of complex behavior if they favored one side over the other, suggesting that maybe these animals were pretty smart.
Now we know that modern octopuses are very intelligent animals.
We've covered that on the podcast But folk are cautious to kind of give these extinct animals an entire backstory based on one bit of them.
It's hard to find out unless we use our obviously very real time machine, Sharmini.
Yeah.
I guess this work does give us a little window into a lost past.
There's so little that remains of these extinct, soft-bodied animals.
And I guess hard to get a sense of what they were really like.
Fine stomach contents, this sort of thing.
But I do think...
These animals are absolutely fascinating.
These giant cephalopods.
Like whenever we see a video of one, I'm like right must watch that right now.
I want to see what it's all about.
You know, it's amazing how you can get so much information from sometimes just such faint markings on a rock.
And I love how it brings to life in my imagination, this kraken-like intelligent giant octopus.
Love that.
Agreed.
A wonderful story and we'll put a link to it in the show notes, along with a link to the story you've talked about today Sharmini.
Listeners, I think that's probably all we've got time for this week.
If you'd like to sign up to The Nature Briefing to get even more stories like this delivered directly to your inbox, then look out for a link in the show notes.
Otherwise, all that remains to be said is Sharmilee Bundell, thank you, as always, for being with me today.
Thanks very much.
And thanks for listening, everyone.
We'll see you next time.
