In this episode of Unfold, you’ll hear about Chonk, a pink, baby-faced axolotl who has become a bit of a superstar on Twitter. This fully aquatic salamander is helping developmental biologists understand neural crest cells. These cells help form our face, skin color and peripheral nervous system. Discovering more about these cells can help researchers understand congenital disorders and certain types of cancer.

In this episode: 

Crystal Rogers, assistant professor, UC Davis Department of Anatomy, Physiology, and Cell Biology at the School of Veterinary Medicine

Audio transcriptions may contain errors.

Crystal Rogers: Need the right key. 

Amy Quinton: Inside a room no bigger than a walk-in closet at the UC Davis School of Veterinary Medicine, shelves are full of small tanks with circulating water. For Assistant Professor Crystal Rogers, a developmental biologist, that sound is meditative. That's because these tanks hold creatures that bring her joy, her precious axolotls, a type of aquatic salamander. 

Crystal Rogers: My axolotls are the leucistic axolotls, which means that they don't have a lot of pigment. They're pink, very cute, probably the cutest ones in my opinion. 

Amy Quinton: Cute, but also a bit alien. These three to eight-inch long creatures have big baby-like faces with large eyes, small limbs and strange magenta external gills that shoot out of their necks like feathers. One axolotl, named Chonk, has become a superstar on Twitter. 

Crystal Rogers: Our newest ones, which include the Twitter-famous Chonk and Chonk siblings, are all one-year-olds, almost exactly. So in fact, wait, they're one-year-olds today. Today's their birthday. Oh, my gosh, how funny. Perfect. Yeah, so today is Chonk's birthday. Oh, man. Chonk deserves more pellets. Like there's got to be something special Chonk and siblings get for a birthday. OK. 

Three pink axolotls in an aquarium
Chonk, the bigger axolotl in the middle, awaits her pellets in her aquarium with her siblings.

Amy Quinton: She grabs forceps and starts to hand feed the pink little monsters, as she calls them. Salmon pellets for dinner. 

Crystal Rogers: They are ravenous eaters. They'll eat anything. And I know this from my graduate lab. We had a pet axolotl there, not a research axolotl. So I know they eat anything, anything, living, anything, you know, anything with protein. 

Amy Quinton: Yep. Chonk even ate a sibling or two before Crystal realized it. Chonk has also grown faster than her siblings. 

Crystal Rogers: She might have a faster metabolism and be able to sort of grow tissue and grow at a faster rate or more efficient at processing the food that we give her. And maybe she grows faster. But we don't honestly know, except for the fact that even as tadpoles, that animal was significantly larger than the rest. So I have no idea. It's pretty amazing. That's actually why Chonk ended up on Twitter, because I was like, “What is this other animal biologist? Please explain.” 

Amy Quinton: Axolotls have all sorts of curious features. Unlike most salamanders that undergo metamorphosis and crawl out of the water to live on land, axolotls decided not to. They retain their juvenile bodies and yet remain fully aquatic and adult. And then there's this. 

Crystal Rogers: Axolotls are this amazing species that have the potential to regenerate almost any part of their body. 

Amy Quinton: That's right. They can regrow limbs and gills and even their spinal cord. And she believes that ability starts while they're embryos. As a developmental biologist, she's breeding them for embryonic research. 

Crystal Rogers: We try to understand the recipe that makes the variety of life. So we try to understand how organisms go from single cells to complex adult organisms. And if we understand that, we will have a better idea of what happens when things go wrong. And if we can understand that, it gives us a better idea of how we got here and how we evolved into these creatures. I mean, I really do think there's so much there still to be discovered. 

Amy Quinton: These cute, pink little monsters with regenerative powers may help us learn a lot about ourselves. In this episode of Unfold, we look at Chonk the axolotl and how life is super amazing. 

Theme: Coming to you from UC Davis, this is Unfold, a podcast that breaks down complicated problems and unfolds curiosity driven research. I'm Amy Quinton. 

Kat Kerlin: And I'm Kat Kerlin. 

Amy Quinton: Crystal Rogers has a lot of axolotls, Kat. 

Kat Kerlin: A lot of axolotls? Say that fast three times. 

Amy Quinton: It's not just Chonk and siblings. All told, Crystal has 43 axolotls. 

Kat Kerlin : Whoa, and they are all so cute. But her love for developmental biology did not start out with an axolotl. 

Amy Quinton: Nope. Instead, she fell in love with a frog, an African claw-toed frog to be exact. 

Crystal Rogers: My immediate reaction to watching an animal go from one cell to like a tadpole or a frog was, “Holy cow. This is it. Like, this is my thing. This is where I'm meant to be.” So I've been enamored with changing embryos since 2003 when I started grad school. 

Amy Quinton: Now she studies axolotl embryos. And Crystal says that at that stage they look nothing like pink little monsters. 

Crystal Rogers: Their embryos don't look at all like them. So they come out as these little brown balls. And for the stuff we do, we generally do any of our experiments within the first week of development so they're not even tadpoles at that point. They're just these little, little, they look like empanadas. So I actually called them that and my student was like messaging on Slack and he's like, “OK, well, I think they're empanada stage.” And I was like, “Just so you know, that's not a real stage. That's just what I call them. So don't use that if you go to a conference. Don't tell people you did empanada stage experiments.” 

Kat Kerlin: So her goal is to understand how environmental or genetic changes affect the axolotl's development. She's looking at the factors that go into making specific types of cells called neural crest cells. 

Amy Quinton: These are stem-like cells that in humans make more than 30 different kinds of tissue. 

Crystal Rogers: So they make the craniofacial bone and cartilage. So the reason we all look different and have different faces is because of our neural crest cells. They make pigment cells, so that gives us our outer coloring. But it also gives animals their designs. They make the peripheral nervous system and the enteric nervous system. So the nervous system that allows us to sense things and since the outside world and also to digest food, neural crest. 

Kat Kerlin: It's what gives Chonk her big baby face and pink color. 

Amy Quinton: And it's why she can sense something in the water and digest yummy salmon pellets. Crystal says neural crest cells are totally cool. 

Crystal Rogers: Part of the reason I'm enamored with them is that like, “How does this happen? How would this have evolved?” I mean, it's hard to think about the cell type and all the different things they make. And there are no other tissue or cell types that make such a variety of different things than this cell type. 

Kat Kerlin: So imagine what would happen if something went wrong with these cells. Like what if they were to develop abnormally in humans? 

Crystal Rogers: A few of the common congenital disorders that you might have heard of are craniofacial clefts like cleft lip and cleft palate. Other things like albinism are caused by abnormal neural cell development. There are neural crest derived cancers, so neuroblastoma and pheochromocytoma are both derived from essentially cells that started as neural crest cells and went a little haywire in either children or adults. 

Amy Quinton: Understanding more about these cells may help us determine how pediatric and other cancers develop. Crystal says in order for cancer tumors of any type to metastasize or spread, they have to turn on neural crest genes. 

Kat Kerlin: Crystal gave us a personal example. 

Crystal Rogers: My mom had breast cancer and I was scanning the sheets to make sure she didn't have this one factor that I know is necessary for both neural crest migration and metastasis and she didn't. And so it was like, “Whew, okay, so you don't have the migratory kind. You have just an epithelial kind and that's like a solid tumor. That's something that can be cut out and fixed, right?” And so if we understand the basic biology of these cells, not only will we be able to identify if embryos are developing and might have congenital disorders, but we can also take that biology and see how that has changed to make diseases. 

Amy Quinton: Crystal describes herself as a mechanistic scientist, so she looks at the molecular mechanisms that drive the formation of these neural crest cells. And she's been surprised by what she's discovered by looking at different species. 

Crystal Rogers: I'm amazed by how similar the programs are across species that make these cells but yet the animals, and even within a species, people look different or animals look different. And so if you have the same genetic recipe to make these cells, how do differences occur at all? And so that's one of the things we study in my lab is trying to define the differences between these cells across species, because I think that will give us an idea for where the differences occur. 

Kat Kerlin: That's why she's not just studying axolotl embryos, but also chicken, quail and even peafowl embryos. That's peacocks to you and me. 

Amy Quinton: And that might sound completely different than how we humans develop, right? But Crystal says the early stages of development of chicken and quail are surprisingly similar to us, even more so than many mammal models. 

Crystal Rogers: At those early stages, they look just like a human embryo. It's honestly if you were to dissect them out at equivalent stages, it would be really hard to tell which was which. And so we do functional experiments in our chicken embryos where we can do gain and loss of function, meaning we overexpress things. We add extra proteins or we knock them down and then we analyze what happens to the neural crest cells and the animal after we do that.

Kat Kerlin: This can help define the pathways that cause diseases like cancers or developmental disorders so that someday we can screen for them or maybe even prevent them. 

Amy Quinton: Crystal says development is like an elegant symphony with perfect timing. 

Crystal Rogers: Knowing what I know about how many pathways had to have worked correctly to get us here, I can't believe it. It's a beautiful design. All of these things have to happen at the right time and place to create this organism and to pattern it and to allow things to form normally. And it's a wonder that it ever happens in that way. I mean, life is super amazing. I'm amazed by science. I'm amazed by life every day. 

Kat Kerlin: You can find links to learn more about Chonk the axolotl and Crystal Rogers research by visiting the Unfold website at 

Amy Quinton: Unfold as a production of UC Davis. It's produced by Cody Drabble. Original music for Unfold comes from Damien Verrett and Curtis Jerome Haynes. Hey, if you like this podcast, check out UC Davis’ other podcast, The Backdrop. It's a monthly interview program featuring conversations with UC Davis scholars and researchers working in the social sciences, humanities, arts and culture. Hosted by public radio veteran Soterios Johnson. The conversations feature new work and expertise on a trending topic in the news. Subscribe wherever you get your podcasts. 

Kat Kerlin: A lot of axolotls. A lot of axolotls. A lot of axolotls. 

More photos and videos of Chonk and the other axolotls