Speaker 1: Welcome to brain Stuff, a production of I Heart Radio,
Speaker 1: Hey brain Stuff Lauren Vogelbaum. Here in Julio Cortaz's short
Speaker 1: story Axelatal, first published in n a Latin American man
Speaker 1: living in Paris becomes infatuated with the axeltles living at
Speaker 1: the zoo, to the point that he eventually transforms into
Speaker 1: one with their quote pink Aztec faces, eyes of gold,
Speaker 1: and rosy little bodies translucent, ending in a ficious tale
Speaker 1: of extraordinary delicacy. The narrator observes a quote absolute lack
Speaker 1: of similarity between axelattles and human beings. In considering these feathery,
Speaker 1: pinkish salamanders, he says, it would seem easy, almost obvious,
Speaker 1: to fall into mythology. Cortisaar's narrator is, on the face
Speaker 1: of things correct in his estimation of the Axelatal for starters,
Speaker 1: the Oxelotal fell into mythology centuries ago. According to Aztec legends,
Speaker 1: the first Oxelotal appeared in the Lake system around modern
Speaker 1: day Mexico City, when the powerful underworld god Zolat transformed
Speaker 1: himself into a small, feathery amphibian to escape capture. In
Speaker 1: ancient Mesoamerican culture, oxelotals were considered a food source supplied
Speaker 1: by Lakes of Jamilico for the good of humanity, and
Speaker 1: Courtsar was right about the oxelotals lack of similarity to humans,
Speaker 1: Our last common ancestor probably roamed earth around three hundred
Speaker 1: and sixty million years ago, and at first or even
Speaker 1: fiftieth glance, they're excessively different from us. Among the first
Speaker 1: modern zoo animals, thirty four oxelotals were brought from Mexico
Speaker 1: to Paris in eighteen sixty four, and although they weren't
Speaker 1: as interesting to nineteenth century zoo goers as the larger,
Speaker 1: more charismatic animals, scientists quickly realized that these unassuming little
Speaker 1: buddies were strange, almost mythological in fact, in the wild,
Speaker 1: oxel attles are or at least used to be top
Speaker 1: predators in their home ecosystem in the lakes and canals
Speaker 1: of central Mexico. They're unusual among amphibians because they remain
Speaker 1: underwater for their entire lives, breathing through gills, while most
Speaker 1: other salamanders walk around on land and breathe with lungs
Speaker 1: during the adult stage of their life. Although they appear
Speaker 1: on assuming they're actually ruthless carnivores feasting on worms, mollusks, insects,
Speaker 1: and even small fish in the wild, and it turns
Speaker 1: out that they have the largest genome of any organism
Speaker 1: yet sequenced. Part of the Aztec mythology of the oxelotal
Speaker 1: centers around the fact that, like a powerful god, they're
Speaker 1: difficult to kill, and that they can regenerate virtually any
Speaker 1: part of their body without much problem. While some lizards
Speaker 1: can grow back a tail bisected, flatworms can grow back
Speaker 1: their other half, and starfish can regrow a limb, an
Speaker 1: oxelotal can regrow its heart, afoot a part of its
Speaker 1: spinal core, you name it. We spoke with David Gardner,
Speaker 1: professor in the School of Biological Sciences at the University
Speaker 1: of California, Irvine. He said, of the animals that are
Speaker 1: closest to us, the vertebrates, salamanders are the only ones
Speaker 1: that can regenerate in this way and can heal without scars.
Speaker 1: Other salamanders can regenerate, but oxelotles do it best. When
Speaker 1: the Europeans got wind of this, oxelotles went from being
Speaker 1: a sort of boring exhibit in the zoo to one
Speaker 1: of the most important and the longest self sustaining lab
Speaker 1: animals in history. George Couvey, popularly considered the father of paleontology,
Speaker 1: studied axelottles in an attempt to figure out whether Carl
Speaker 1: Linneus was correct in categorizing the classes Amphibia and reptilia separately.
Speaker 1: It was a big question in those days. Covie incorrectly
Speaker 1: concluded the oxelotles, because they breathe through gills their entire lives,
Speaker 1: must be some sort of lizard that existed as a
Speaker 1: perpetual law va, in the words of paleontologists Stephen Jay
Speaker 1: Gold quote a sexually mature tadpole. Couvy was correct sometimes,
Speaker 1: but not in this case. And because oxeltles did incredibly
Speaker 1: well in laboratory and aquarium settings, a nineteenth century zoologist
Speaker 1: took it upon himself to provide every lab in Europe
Speaker 1: with a supply of them, which resulted in some truly
Speaker 1: horrific studies in which scientists chopped them up just to
Speaker 1: test the limits of their regenerative powers. Gardner said, these days,
Speaker 1: oxyletles are hugely important model systems for our studies about regeneration.
Speaker 1: We've known for decades, centuries even that we can remove
Speaker 1: parts of a developing embryonic structure and the cells that
Speaker 1: are left behind will fill in, repair, and regenerate that structure.
Speaker 1: But in most animals and mammals, for instance, the system
Speaker 1: sort of shuts down at the end of embryonic development.
Speaker 1: Salamanders seem to be able to revert back to that
Speaker 1: embryonic like state, re accessing the developmental program that's already there.
Speaker 1: Humans have the program, we just stop being able to
Speaker 1: access it when we're no longer an embryo. You could say, we,
Speaker 1: like oxylottles, have evolved the ability to regenerate just fine,
Speaker 1: but we've also evolved a mechanism that inhibits that. Oxeltles
Speaker 1: can endure a lot, but they have not been able
Speaker 1: to endure their home ecosystem, being overrun with introduced predators
Speaker 1: and environmental toxins. The lakes in their home around ultra
Speaker 1: urbanized Mexico City have become not only polluted by aging
Speaker 1: wastewater systems, but overrun by introduced telapia and perch, both
Speaker 1: of which view oxylottles as a delicious snack. Scientists counted
Speaker 1: around six thousand oxeltals per square kilometer in Lake Zotomilco,
Speaker 1: but these days fewer than thirty five animals take up
Speaker 1: the same amount of space. It looks like the oxylottle
Speaker 1: is on the fast track to extinction even in their
Speaker 1: home environment, which is something of a paradox like the
Speaker 1: oxelottle itself. While wild oxelttles are critically endangered, they're doing
Speaker 1: great in captivity. They're the most widely distributed amphibian in
Speaker 1: the world. Millions of them live in labs around the globe,
Speaker 1: many more in fact, than live in the wild now,
Speaker 1: and while they're important in science, they're also quite popular
Speaker 1: in pet shops. Today's episode was written by Jesslin Shields
Speaker 1: and produced by Tyler Clang. For more on this and
Speaker 1: lots of other regenerative topics, visit how stuff works dot com.
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