Briefing chat: Spinosaurs with salt glands could have lived in marine environments

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1:08Hi, listeners. Benjamin here. Welcome to The Briefing Show, the Friday podcast where we talk about a few stories we've read about in The Nature Briefing, which is, of course, nature's daily email roundup of the latest science news. We've got a couple of stories to talk about today. And joining me to do so is the one and only Maren Huntsberger. Maren, how are you doing? Hello, hello. I'm doing great. I'm really excited to talk to you today about dinosaurs. Have at it then. Let's go. Dinosaurs, what's going on with them? This story is about a particularly charismatic looking dinosaur. It's called the Spinosaurus, Ben.

1:40And it's called a Spinosaurus because it has these elongated vertebrae on its back, which support this big membrane. So it has this thing protruding off its back that makes it look like a big sail. And Spinosauruses typically tended to live in more coastal areas. And there's been a lot of debate amongst paleontologists throughout the years just how much of their lives exactly they spent aquatically versus on land. And now there's paper out in historical biology. I read an article about this in Science. And that has some new evidence shedding a little bit more light on where these Spinosauruses may have actually lived.

2:13Oh, right. Because I guess it's really hard to work out what an animal's behavior was like from its bones. So how have they gone about working out whereabouts it may have paddled, I suppose? Exactly. Well, it's very tricky to piece things together like that from the fossil record, but there are certain parts of its anatomy that indicate that it might have had these big paddle-like fins to swim around with. But this new evidence is about something called the supra-orbitally placed salt gland, Ben, or more catchly known as the SSG. Oh, the SSG, right. You've said orbital there. I'm guessing this isn't to do with space.

2:50What is this? Correct eyeballs, Ben. So there's lots of evolutionary considerations that come with living in a salty environment, right? If something's coastal, that means that you're by the sea, therefore that comes with salt. And obviously our bodies have to maintain a really careful balance of salt in order to remain functional. All of our cells rely on osmotic balance, right? Fluid flowing from one area to another to maintain the ideal ratio of salt. So animals that live in coastal environments and that eat a lot of fish maybe have to work really hard to maintain their body's osmotic balance.

3:25Animals today that have to contend with this are things like crocodiles that often live in marshy, brackish areas. They have a specialized gland that allows them to excrete excess salt. Marine iguanas also have these. Fun fact, alligators don't have this gland, which is why they actually have to return periodically to fresh water so they can maintain their osmotic balance. And marine birds also have this specialized gland. So in this new paper, the researchers found evidence that at least some Spinosauruses also had these supraorbitally placed salt glands, which indicates that they had to have a way to excrete excess salt, which means they were living in a salty area, which means we might now have more evidence for the aquatic side of the argument than we had before.

4:10Right. I mean, I guess certainly when it comes to thinking about birds, there is a through line between our avian friends and the dinosaurs. Yes, exactly. And actually, one of my favorite lines from this paper is the first one from the abstract, which is, despite their exceptional diversification on land, non-avian dinosaurs barely exploited the marine realm, which seems like a little bit of a dunk on the dinosaurs. But this paper posits that potentially that was because of this specialized cranial anatomy that is required to excrete excess salt. Birds could do it so they were able to diversify into more marine environments.

4:47But fewer dinosaurs were able to exploit this more amphibious area between land and the ocean. Except the Spinosaurus then, which evidence suggests was getting it done. Obviously, anything to do with fossils is difficult because you're making inferences. is what did the researchers do in this instance to lead them to think that there was this gland? Yeah, it's absolutely incredible. You know, as a non-paleontologist, I'm looking at the pictures in the paper and I'm like, I don't know what you guys are seeing. But obviously, they are so familiar with dinosaur anatomy and how that's evidenced in the bones that they find that they can tell which divots are, you know, actually anatomically included in the fossil versus, you know, just weathering or due to the way it was dug out of the ground.

5:27And I think a great quote that reflects this is a paleontologist at Queen Mary University, David Hone, who wasn't involved in the research, puts it perfectly when he says, it's impressive that these researchers were able to draw out this data from very limited fossil remains. So even the most subtle, tiny indentations and divots in dinosaur fossils can tell us so much about how they may have lived their lives. I love a dinosaur story. I think everybody loves a dinosaur story, right?

5:58Don't might have been like is welcome news. But let's move on to my story this week. And wake up, Marin. A new type of cell death has just dropped, and it's explosive. Whoa, what a headline. I know, right? Well, this is a story I read about in Nature, and it's based on a paper in Cell. And it's about some newly found immune cells called ruptoblasts. Whoa, also, what a name. That's fantastic. And they explode when they're triggered and they eject toxic chemicals that can deliver death to surrounding cells really, really quickly, according to this new research. It's like, you know, what you think your immune cells do when you're a kid and you're just learning about how your immune cells fight bad guys.

6:43This is really happening. That's so cool. And it was found by chance, it has to be said. And so the authors of this study were studying a species of planarian flatworm. I hope I'm pronouncing that correctly. Now, planarians are very interesting to scientists. They have these super regenerative capabilities, right? They can be chopped up and the chopped up bits will grow a new worm. I've actually done this in science class in my university education. You can bisect a planarian worm and then there's just two worms. It's wild, right? And they are unusual in a great many ways, including that they lack the immune molecules known as antibodies, which obviously we're very familiar with and which are a very important part of our immune systems.

7:23And yet they are able to mount a robust immune response against pathogens as they regenerate. And of course, the question there is how? And the researchers behind this work were interested in finding out. So they studied these animals at a cellular level, right, really getting into the details there. And they found this quite confusing result. They saw this group of cells that occasionally seemed to rapidly disappear, leaving behind essentially a wasteland strewn with dead cells. Now, this is a bit of a head scratcher. And after confirming that what they were seeing wasn't an artifact, right, this was a real thing, they dubbed these vanishing cells ruptoblasts, as I've said there.

8:08And they've set about characterizing them and working out what they were doing and how they worked. I mean, who needs fancy antibody machinery when you just have a toxic explosion that can decimate anything in the near vicinity? Well, this is exactly right. And it seems that this explosion requires a protein called activin. Now, this is a widely studied hormone associated with cells dividing and immune signaling, all sorts of different things. But in this case, when a ruptoblast detects activin, what happens is the calcium that's stored in this cell sort of shifts and accumulates in a specific place.

8:44So there's a higher concentration of calcium inside the cell than outside. And similar to your story there, right, they have this gradient then. And this then leads to this process of ruptosis where the cell explodes in less than two minutes after sensing this activin. and it releases compounds that kill other cells and lots of other cells. It has to be said, Marin, a single ruptoblast could kill as many as 70 surrounding cells when they were tested in a dish. So we had bacterial cells, planarian cells, and cells of mammalian origin, including human cells. So it reminds me a little bit of the sort of smart bomb you might come across in video games where it completely clears the screen if you activate it.

9:26It seems that this is what these reptoblasts are doing. That's a big blast radius. But doesn't that mean that the reptoblast would also damage the cells inside the organism's body that it was trying to defend? Absolutely. And what the team have done is they've looked for evidence of this system in other animals too, like genetic evidence and what have you. And it seems that there is some evidence of it existing in other worms. And a lot of these are also capable of regeneration. So their working hypothesis is this kind of indiscriminate defensive response doesn't necessarily matter too much for these organisms because they're so good at mending themselves.

10:06They just sort of shrug it off, I guess. And off they go again. They've killed the invaders. They have this collateral damage. They fix it. And off they wiggle on their wormy way. That makes perfect sense. And I guess that's why humans and other more complex organisms, where we don't have this remarkable regenerative capacity, we do have to be more fine-tuned with our immune response to make sure we're only getting the stuff we mean to, and ideally, not too many of our own cells. Absolutely right. But organisms like us do have specialised pathways that cells use when they need to die for whatever reason.

10:39The most well-known, I guess, is called apoptosis, where cells are gradually demolished and that keeps surrounding tissues healthy. That can take quite a long time. And what's been seen here is really, really quick. So the scientists behind this put forward that this could be a new type of cell death as well. There is a bunch of different types for a bunch of different reasons, but it seems like they've come across quite an unusual one. Well, I always love a story that lets us know how much we still don't know about the world and how much there still is yet to explore. New kinds of cell death, hey?

11:14Who knew? And listeners, if you'd like to learn more about what's going on in the world, we'll put links to these two stories in the show notes so you can read them. And a link to where you can sign up for the Nature Briefing to get even more amazing stuff delivered directly to your inbox. Let's call it there for this week, Maren. Listeners, if you'd like to reach out to us, you can do so on social media. We're at Nature Podcast, or you can send an email to podcast at nature.com. But we have another avenue as well that's been open for a little while. We are very much on TikTok now, and that's something that's being driven by you, Maren.

11:49Yes, we're on TikTok now. We are exploring this new avenue of vertical video for reaching a whole new audience with nature's exciting information and science news. and you can check us out there. We are at nature and we're verified. So make sure you're following the correct nature. Well, I will say that your recent video about the science of red light therapy is already a favorite of mine. And if listeners want to see me trying to talk about a robot while simultaneously balancing a table tennis ball on a table tennis bat, which is more difficult than it looks, that's the place to do it. It's fantastic work, Ben.

12:22You don't want to miss it, listeners. You're ever so kind. Well, listen, we'll call it there then. I've been Benjamin Thompson, Maren Hunsberger. Thank you so much for being here. Thanks for having me. and thanks for listening.

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