1 00:00:01,920 --> 00:00:04,320 Speaker 1: Welcome to brain Stuff, a production of I Heart Radio, 2 00:00:06,280 --> 00:00:11,080 Speaker 1: Hey brain Stuff Lauren Vogelbaum. Here in Julio Cortaz's short 3 00:00:11,119 --> 00:00:16,000 Speaker 1: story Axelatal, first published in n a Latin American man 4 00:00:16,120 --> 00:00:19,880 Speaker 1: living in Paris becomes infatuated with the axeltles living at 5 00:00:19,880 --> 00:00:23,600 Speaker 1: the zoo, to the point that he eventually transforms into 6 00:00:23,600 --> 00:00:27,400 Speaker 1: one with their quote pink Aztec faces, eyes of gold, 7 00:00:27,440 --> 00:00:31,000 Speaker 1: and rosy little bodies translucent, ending in a ficious tale 8 00:00:31,000 --> 00:00:36,720 Speaker 1: of extraordinary delicacy. The narrator observes a quote absolute lack 9 00:00:36,760 --> 00:00:42,960 Speaker 1: of similarity between axelattles and human beings. In considering these feathery, 10 00:00:43,120 --> 00:00:47,400 Speaker 1: pinkish salamanders, he says, it would seem easy, almost obvious, 11 00:00:47,560 --> 00:00:52,920 Speaker 1: to fall into mythology. Cortisaar's narrator is, on the face 12 00:00:52,960 --> 00:00:57,120 Speaker 1: of things correct in his estimation of the Axelatal for starters, 13 00:00:57,240 --> 00:01:01,880 Speaker 1: the Oxelotal fell into mythology centuries ago. According to Aztec legends, 14 00:01:01,920 --> 00:01:04,920 Speaker 1: the first Oxelotal appeared in the Lake system around modern 15 00:01:05,000 --> 00:01:09,160 Speaker 1: day Mexico City, when the powerful underworld god Zolat transformed 16 00:01:09,240 --> 00:01:13,520 Speaker 1: himself into a small, feathery amphibian to escape capture. In 17 00:01:13,640 --> 00:01:17,440 Speaker 1: ancient Mesoamerican culture, oxelotals were considered a food source supplied 18 00:01:17,480 --> 00:01:21,000 Speaker 1: by Lakes of Jamilico for the good of humanity, and 19 00:01:21,240 --> 00:01:25,160 Speaker 1: Courtsar was right about the oxelotals lack of similarity to humans, 20 00:01:25,520 --> 00:01:28,760 Speaker 1: Our last common ancestor probably roamed earth around three hundred 21 00:01:28,800 --> 00:01:32,360 Speaker 1: and sixty million years ago, and at first or even 22 00:01:32,480 --> 00:01:37,720 Speaker 1: fiftieth glance, they're excessively different from us. Among the first 23 00:01:37,840 --> 00:01:41,720 Speaker 1: modern zoo animals, thirty four oxelotals were brought from Mexico 24 00:01:41,880 --> 00:01:45,600 Speaker 1: to Paris in eighteen sixty four, and although they weren't 25 00:01:45,640 --> 00:01:48,840 Speaker 1: as interesting to nineteenth century zoo goers as the larger, 26 00:01:48,960 --> 00:01:54,000 Speaker 1: more charismatic animals, scientists quickly realized that these unassuming little 27 00:01:54,000 --> 00:01:59,559 Speaker 1: buddies were strange, almost mythological in fact, in the wild, 28 00:01:59,600 --> 00:02:02,640 Speaker 1: oxel attles are or at least used to be top 29 00:02:02,680 --> 00:02:05,640 Speaker 1: predators in their home ecosystem in the lakes and canals 30 00:02:05,640 --> 00:02:10,240 Speaker 1: of central Mexico. They're unusual among amphibians because they remain 31 00:02:10,320 --> 00:02:14,160 Speaker 1: underwater for their entire lives, breathing through gills, while most 32 00:02:14,200 --> 00:02:17,360 Speaker 1: other salamanders walk around on land and breathe with lungs 33 00:02:17,440 --> 00:02:21,080 Speaker 1: during the adult stage of their life. Although they appear 34 00:02:21,120 --> 00:02:26,440 Speaker 1: on assuming they're actually ruthless carnivores feasting on worms, mollusks, insects, 35 00:02:26,520 --> 00:02:29,720 Speaker 1: and even small fish in the wild, and it turns 36 00:02:29,720 --> 00:02:32,480 Speaker 1: out that they have the largest genome of any organism 37 00:02:32,600 --> 00:02:36,839 Speaker 1: yet sequenced. Part of the Aztec mythology of the oxelotal 38 00:02:36,960 --> 00:02:40,680 Speaker 1: centers around the fact that, like a powerful god, they're 39 00:02:40,720 --> 00:02:44,400 Speaker 1: difficult to kill, and that they can regenerate virtually any 40 00:02:44,480 --> 00:02:49,040 Speaker 1: part of their body without much problem. While some lizards 41 00:02:49,080 --> 00:02:52,160 Speaker 1: can grow back a tail bisected, flatworms can grow back 42 00:02:52,200 --> 00:02:55,720 Speaker 1: their other half, and starfish can regrow a limb, an 43 00:02:55,720 --> 00:02:59,320 Speaker 1: oxelotal can regrow its heart, afoot a part of its 44 00:02:59,360 --> 00:03:04,000 Speaker 1: spinal core, you name it. We spoke with David Gardner, 45 00:03:04,240 --> 00:03:07,120 Speaker 1: professor in the School of Biological Sciences at the University 46 00:03:07,120 --> 00:03:10,920 Speaker 1: of California, Irvine. He said, of the animals that are 47 00:03:10,960 --> 00:03:14,480 Speaker 1: closest to us, the vertebrates, salamanders are the only ones 48 00:03:14,560 --> 00:03:17,880 Speaker 1: that can regenerate in this way and can heal without scars. 49 00:03:18,360 --> 00:03:23,920 Speaker 1: Other salamanders can regenerate, but oxelotles do it best. When 50 00:03:24,040 --> 00:03:27,160 Speaker 1: the Europeans got wind of this, oxelotles went from being 51 00:03:27,240 --> 00:03:29,880 Speaker 1: a sort of boring exhibit in the zoo to one 52 00:03:29,919 --> 00:03:33,120 Speaker 1: of the most important and the longest self sustaining lab 53 00:03:33,160 --> 00:03:39,240 Speaker 1: animals in history. George Couvey, popularly considered the father of paleontology, 54 00:03:39,560 --> 00:03:42,640 Speaker 1: studied axelottles in an attempt to figure out whether Carl 55 00:03:42,720 --> 00:03:48,200 Speaker 1: Linneus was correct in categorizing the classes Amphibia and reptilia separately. 56 00:03:48,720 --> 00:03:52,520 Speaker 1: It was a big question in those days. Covie incorrectly 57 00:03:52,600 --> 00:03:56,400 Speaker 1: concluded the oxelotles, because they breathe through gills their entire lives, 58 00:03:56,800 --> 00:03:59,160 Speaker 1: must be some sort of lizard that existed as a 59 00:03:59,160 --> 00:04:03,040 Speaker 1: perpetual law va, in the words of paleontologists Stephen Jay 60 00:04:03,120 --> 00:04:08,880 Speaker 1: Gold quote a sexually mature tadpole. Couvy was correct sometimes, 61 00:04:08,880 --> 00:04:14,360 Speaker 1: but not in this case. And because oxeltles did incredibly 62 00:04:14,360 --> 00:04:18,479 Speaker 1: well in laboratory and aquarium settings, a nineteenth century zoologist 63 00:04:18,520 --> 00:04:21,280 Speaker 1: took it upon himself to provide every lab in Europe 64 00:04:21,320 --> 00:04:24,479 Speaker 1: with a supply of them, which resulted in some truly 65 00:04:24,560 --> 00:04:27,400 Speaker 1: horrific studies in which scientists chopped them up just to 66 00:04:27,480 --> 00:04:32,760 Speaker 1: test the limits of their regenerative powers. Gardner said, these days, 67 00:04:32,760 --> 00:04:37,440 Speaker 1: oxyletles are hugely important model systems for our studies about regeneration. 68 00:04:38,040 --> 00:04:41,120 Speaker 1: We've known for decades, centuries even that we can remove 69 00:04:41,240 --> 00:04:44,320 Speaker 1: parts of a developing embryonic structure and the cells that 70 00:04:44,360 --> 00:04:48,120 Speaker 1: are left behind will fill in, repair, and regenerate that structure. 71 00:04:48,920 --> 00:04:52,320 Speaker 1: But in most animals and mammals, for instance, the system 72 00:04:52,440 --> 00:04:55,120 Speaker 1: sort of shuts down at the end of embryonic development. 73 00:04:55,760 --> 00:04:58,479 Speaker 1: Salamanders seem to be able to revert back to that 74 00:04:58,640 --> 00:05:03,719 Speaker 1: embryonic like state, re accessing the developmental program that's already there. 75 00:05:04,520 --> 00:05:07,200 Speaker 1: Humans have the program, we just stop being able to 76 00:05:07,240 --> 00:05:10,359 Speaker 1: access it when we're no longer an embryo. You could say, we, 77 00:05:10,839 --> 00:05:14,640 Speaker 1: like oxylottles, have evolved the ability to regenerate just fine, 78 00:05:15,040 --> 00:05:21,320 Speaker 1: but we've also evolved a mechanism that inhibits that. Oxeltles 79 00:05:21,400 --> 00:05:24,120 Speaker 1: can endure a lot, but they have not been able 80 00:05:24,160 --> 00:05:28,039 Speaker 1: to endure their home ecosystem, being overrun with introduced predators 81 00:05:28,080 --> 00:05:32,040 Speaker 1: and environmental toxins. The lakes in their home around ultra 82 00:05:32,200 --> 00:05:35,839 Speaker 1: urbanized Mexico City have become not only polluted by aging 83 00:05:35,880 --> 00:05:40,680 Speaker 1: wastewater systems, but overrun by introduced telapia and perch, both 84 00:05:40,680 --> 00:05:46,200 Speaker 1: of which view oxylottles as a delicious snack. Scientists counted 85 00:05:46,240 --> 00:05:50,600 Speaker 1: around six thousand oxeltals per square kilometer in Lake Zotomilco, 86 00:05:50,800 --> 00:05:53,919 Speaker 1: but these days fewer than thirty five animals take up 87 00:05:53,920 --> 00:05:57,200 Speaker 1: the same amount of space. It looks like the oxylottle 88 00:05:57,320 --> 00:05:59,800 Speaker 1: is on the fast track to extinction even in their 89 00:05:59,800 --> 00:06:03,680 Speaker 1: home environment, which is something of a paradox like the 90 00:06:03,720 --> 00:06:09,159 Speaker 1: oxelottle itself. While wild oxelttles are critically endangered, they're doing 91 00:06:09,200 --> 00:06:13,159 Speaker 1: great in captivity. They're the most widely distributed amphibian in 92 00:06:13,200 --> 00:06:16,440 Speaker 1: the world. Millions of them live in labs around the globe, 93 00:06:16,880 --> 00:06:19,320 Speaker 1: many more in fact, than live in the wild now, 94 00:06:20,080 --> 00:06:23,160 Speaker 1: and while they're important in science, they're also quite popular 95 00:06:23,320 --> 00:06:31,200 Speaker 1: in pet shops. Today's episode was written by Jesslin Shields 96 00:06:31,200 --> 00:06:33,320 Speaker 1: and produced by Tyler Clang. For more on this and 97 00:06:33,400 --> 00:06:36,760 Speaker 1: lots of other regenerative topics, visit how stuff works dot com. 98 00:06:36,880 --> 00:06:39,560 Speaker 1: Brain Stuff is production of iHeart Radio or more podcasts. 99 00:06:39,640 --> 00:06:42,359 Speaker 1: My Heart Radio visit the iHeart Radio app, Apple Podcasts, 100 00:06:42,440 --> 00:06:44,120 Speaker 1: or wherever you listen to your favorite shows.