Shownotes Transcript
Hello, I'm Hannah Gelbart and you're listening to What in the World from the BBC World Service. Have you heard of axolotls? They're one of the world's most endangered and arguably most adorable amphibians. They can grow to around 30 centimetres and they're from Mexico, but they've nearly gone extinct in the wild. Now there is hope. A
A study has released captive-bred axolotls into a restored wetland near Mexico City, and it found that they not only survived, they thrive. And beyond their smiling little faces, these creatures are scientifically fascinating too. They can even regrow lost limbs. So today, you're going to hear how axolotls are being brought back from the brink, and what scientists can learn from these amazing creatures. ♪
Firstly, before we get into the science, let's hear how popular they are in their native country, Mexico. This is researcher Alejandra Ramos, who led the study. In Mexico, like we made one of our currency, one of our bills. It has an axelot now. This is fairly new. But once it came out, people loved it so much that they didn't want to spend it.
So people were just keeping the 50 pesos axolotl bill in their house and nobody wanted to spend it. And like this even became an issue, you know, because people were not spending that. There's so much love for the axolots from all over the world. So many people. I think there will be many people very sad if we don't save the wild axolotl. To find out more, I'm speaking to Victoria Gill, the BBC science correspondent. Hi. Hi, Hannah. How are you? Yeah, great to speak to you again.
For people who haven't seen an axolotl, can you tell me what they look like and where they live? Oh, you might have to cut me off because I could wax lyrical about axolotls. Apart from my dog, I think they're my favourite animal. So these are salamanders. They're amphibians. They sort of look like little newts or lizards, but they live in the water. And unlike other amphibians, which have this
kind of interesting life cycle where they as babies like you can think of like tadpoles and frogs as babies they're in a kind of larval stage and they live in the water and then they come out of the water and they grow legs and they change but axolotls don't do that they live in this kind of perpetual juvenile state they sort of call them the Peter Pan of the amphibian world and
And because of that, they have legs, but they also have these feathery gills around their faces. They've got this extraordinary little face with what looks like a little smile on their face. I would highly recommend a Google image search of an axolotl. They're incredibly cute.
And they live naturally in terms of like their native wild habitat. They live in just one place, which is very close to Mexico City, a city of 20 million people. But just to the south, there is this area of wetlands and canals and this kind of traditional farmland that's surrounded by these canal systems called Xochimilco. And that's where these salamanders live. That's where the axolotl lives. I had a look at some pictures of axolotls online and you can't help smiling when you see them because they've got this like big,
permanent grin on their little faces. They are one of the most endangered amphibians in the world. Why is it that their numbers have been falling? Yeah, they are. They might be the most critically endangered. It's difficult to gauge what their exact population is. At the lowest ebb, I think the estimates were that there were between 50 and 1,000 left in the wild. But there used to be thousands and thousands, hundreds of thousands of them sort of teeming in these waters in
in Xochimilco. And there's a number of things that happened and it's over the last few decades really. And one of the things was that the water into this wetland used to come from the mountains. It was this spring water that came from the mountains. And
And as Mexico City grew, you know, there's more than 21 million people live in Mexico City. Demand for water meant that that was redirected to sort of fuel the city and provide for the city. And the water supply to Xochimilco then came from a water treatment plant. And there were problems with that water. You know, sometimes the water quality was quite low. And that also, this kind of this redistribution sort of brought in invasive species as well, other species that competed.
or the fish that competed for food and also ate the axolotls' eggs and actually fed on them when they were young. So all of these things have combined this kind of pollution, the growth of Mexico City to just drive those numbers down over the years. So there used to be thousands per square kilometer over this population
vast wetland in Xochimilco and when I talked to researchers a few years ago who were trying to restore these sites to bring the axolotl back and they said there were just dozens maybe per square kilometre and they were really difficult to find.
And there has been this study recently monitoring axolotls. How exactly were they monitored? So it's sort of a two-pronged approach. These researchers, led by Luis Zambrano, who's based in Mexico City, he's a conservation scientist,
have been working for many years with the farmers in Xochimilco who farm these traditional canals surrounded little islands called chinampas to create refuges for the axolotls and kind of clean up that environment. So that was the first part of it. That's the foundation.
The next part is that they captive bred axolotls and then they've just recently taken some of those captive reared axolotls and released them into a wetland site in Xochimilco and another site that was restored as well nearby.
And the way they track them is they actually put tiny little radio transmitters on the axolotls so that they can use just these big antennae. They can sort of stand on the banks or sit in a boat and actually track their movements. And they just produce a little kind of bleeping sound when their transmitter is near the radio antenna. And what did they find?
It's really good news. They released 18 and every single one of them survived. And not only that, the ones that they recaptured, they recaptured about half a dozen of them and they had gained weight. And what that means is that they're hunting. And that's really important because you can imagine growing up in the wild as any wild animal is very different from being reared in a tank and being just fed wild.
food every day. So they're really concerned that these animals just wouldn't know how to be wild, wouldn't know how to hunt, might get taken by predators. But they've done really well, which is great news because it means that with this standby population of captive axolotls, it gives us hope for bringing them back to Xochimilco, to their native wetland in the future. But there's a lot more work to do to get that
place in a state where this population can thrive again. There's something quite unique scientifically about the axolotl. They can regenerate their own limbs when they have an injury or lose a limb. How does that work? Yes, they're amazing. They stay in this perpetual state of juvenility. And I think that might have something to do with this sort of strange life cycle of theirs where they never quite grow up.
might have some connection with their constant regeneration. So with the fact that they can just heal and regrow. They're remarkable animals. In Mexico, you know, which is their native home, they are a cultural icon. They feature in art.
They feature in street art now. They are loved and they're something of an emblem. There's also a legend about this animal that it's actually a god, an Aztec god in salamander form. And I think that's related to what you said, this ability that if an axolotl is injured, if it loses an entire limb, it can just regrow that whole limb. It could regrow its brain. It could regrow its spinal cord.
It's an extraordinary thing. And it's sort of why there's this strange scientific irony around axolotls, because while they're really struggling in the wild and there's all these efforts to bring them back and protect them, there's about an estimated one million of them in laboratories and in home aquariums around the world.
as pets because they're very cute and they're really interesting, but in labs because scientists are very interested to find out why it is they can regrow a limb. Now let's hear from someone working in this area. Hi, my name is Prayag Murawala. I am an assistant professor at Mount Desert Island Biological Laboratory in USA. If an axolotl loses a limb, it's no big deal. It can simply grow a new one.
But there is a lot going on behind the scenes. The axolotl's body has to figure out exactly where the limb was lost, what needs to grow back and how much to regenerate. You wouldn't want a limb that's too short or too long. It has to be an exact copy of what was lost. Just like your arm or leg, an axolotl's limb is made up of many different types of cells.
including skin, muscles, nerves, bones, blood vessels and many more. To successfully regenerate a limb, all these different cell types must work together perfectly. They also have to grow in the correct pattern, making sure that limb has exactly the right number of fingers. What's even more fascinating is how these cells communicate.
They turn on hundreds of different genes at exactly the right times and places, almost like they are talking to each other.
Back to you, Victoria. How are scientists using this knowledge? So there's genetic studies going on in one lab in the UK, in the University of Edinburgh in Scotland at the moment, looking at how they regenerate their spinal cords. So they're trying to figure out what is going on in terms of the blueprint and cell activity when an axolotl has an injured spinal cord. What's going on there when its cells sort of rearrange itself and build new spinal cord?
The long-term idea being, and it's early genetic research, but the long-term idea being that if we can understand that in depth, then maybe we can figure out how to harness that medically, how we could repair spinal cord or sort of have spinal cord self-repair in humans. Vic, thank you so much for coming on the podcast. I think axolotls are my new favourite animal. Oh, good. I've sold them on you. Thank you very much, Hannah. Definitely. Don't tell my dog.
Thank you very much, Hannah. My pleasure. Thank you. Bye. Bye. And thank you for listening. If you want to hear more of our episodes with Vic Gill, we've talked about why scientists want to bring back extinct animals and also what happened when Katy Perry popped into space. You can find those wherever you get your BBC podcasts. I'm Hannah Gelbart. This is What In The World from the BBC World Service. We'll see you next time. Bye. Bye.