WEBVTT - How Do Axolotls Work? 0:00:01.920 --> 0:00:04.320 Welcome to brain Stuff, a production of I Heart Radio, 0:00:06.280 --> 0:00:11.080 Hey brain Stuff Lauren Vogelbaum. Here in Julio Cortaz's short 0:00:11.119 --> 0:00:16.000 story Axelatal, first published in n a Latin American man 0:00:16.120 --> 0:00:19.880 living in Paris becomes infatuated with the axeltles living at 0:00:19.880 --> 0:00:23.600 the zoo, to the point that he eventually transforms into 0:00:23.600 --> 0:00:27.400 one with their quote pink Aztec faces, eyes of gold, 0:00:27.440 --> 0:00:31.000 and rosy little bodies translucent, ending in a ficious tale 0:00:31.000 --> 0:00:36.720 of extraordinary delicacy. The narrator observes a quote absolute lack 0:00:36.760 --> 0:00:42.960 of similarity between axelattles and human beings. In considering these feathery, 0:00:43.120 --> 0:00:47.400 pinkish salamanders, he says, it would seem easy, almost obvious, 0:00:47.560 --> 0:00:52.920 to fall into mythology. Cortisaar's narrator is, on the face 0:00:52.960 --> 0:00:57.120 of things correct in his estimation of the Axelatal for starters, 0:00:57.240 --> 0:01:01.880 the Oxelotal fell into mythology centuries ago. According to Aztec legends, 0:01:01.920 --> 0:01:04.920 the first Oxelotal appeared in the Lake system around modern 0:01:05.000 --> 0:01:09.160 day Mexico City, when the powerful underworld god Zolat transformed 0:01:09.240 --> 0:01:13.520 himself into a small, feathery amphibian to escape capture. In 0:01:13.640 --> 0:01:17.440 ancient Mesoamerican culture, oxelotals were considered a food source supplied 0:01:17.480 --> 0:01:21.000 by Lakes of Jamilico for the good of humanity, and 0:01:21.240 --> 0:01:25.160 Courtsar was right about the oxelotals lack of similarity to humans, 0:01:25.520 --> 0:01:28.760 Our last common ancestor probably roamed earth around three hundred 0:01:28.800 --> 0:01:32.360 and sixty million years ago, and at first or even 0:01:32.480 --> 0:01:37.720 fiftieth glance, they're excessively different from us. Among the first 0:01:37.840 --> 0:01:41.720 modern zoo animals, thirty four oxelotals were brought from Mexico 0:01:41.880 --> 0:01:45.600 to Paris in eighteen sixty four, and although they weren't 0:01:45.640 --> 0:01:48.840 as interesting to nineteenth century zoo goers as the larger, 0:01:48.960 --> 0:01:54.000 more charismatic animals, scientists quickly realized that these unassuming little 0:01:54.000 --> 0:01:59.559 buddies were strange, almost mythological in fact, in the wild, 0:01:59.600 --> 0:02:02.640 oxel attles are or at least used to be top 0:02:02.680 --> 0:02:05.640 predators in their home ecosystem in the lakes and canals 0:02:05.640 --> 0:02:10.240 of central Mexico. They're unusual among amphibians because they remain 0:02:10.320 --> 0:02:14.160 underwater for their entire lives, breathing through gills, while most 0:02:14.200 --> 0:02:17.360 other salamanders walk around on land and breathe with lungs 0:02:17.440 --> 0:02:21.080 during the adult stage of their life. Although they appear 0:02:21.120 --> 0:02:26.440 on assuming they're actually ruthless carnivores feasting on worms, mollusks, insects, 0:02:26.520 --> 0:02:29.720 and even small fish in the wild, and it turns 0:02:29.720 --> 0:02:32.480 out that they have the largest genome of any organism 0:02:32.600 --> 0:02:36.839 yet sequenced. Part of the Aztec mythology of the oxelotal 0:02:36.960 --> 0:02:40.680 centers around the fact that, like a powerful god, they're 0:02:40.720 --> 0:02:44.400 difficult to kill, and that they can regenerate virtually any 0:02:44.480 --> 0:02:49.040 part of their body without much problem. While some lizards 0:02:49.080 --> 0:02:52.160 can grow back a tail bisected, flatworms can grow back 0:02:52.200 --> 0:02:55.720 their other half, and starfish can regrow a limb, an 0:02:55.720 --> 0:02:59.320 oxelotal can regrow its heart, afoot a part of its 0:02:59.360 --> 0:03:04.000 spinal core, you name it. We spoke with David Gardner, 0:03:04.240 --> 0:03:07.120 professor in the School of Biological Sciences at the University 0:03:07.120 --> 0:03:10.920 of California, Irvine. He said, of the animals that are 0:03:10.960 --> 0:03:14.480 closest to us, the vertebrates, salamanders are the only ones 0:03:14.560 --> 0:03:17.880 that can regenerate in this way and can heal without scars. 0:03:18.360 --> 0:03:23.920 Other salamanders can regenerate, but oxelotles do it best. When 0:03:24.040 --> 0:03:27.160 the Europeans got wind of this, oxelotles went from being 0:03:27.240 --> 0:03:29.880 a sort of boring exhibit in the zoo to one 0:03:29.919 --> 0:03:33.120 of the most important and the longest self sustaining lab 0:03:33.160 --> 0:03:39.240 animals in history. George Couvey, popularly considered the father of paleontology, 0:03:39.560 --> 0:03:42.640 studied axelottles in an attempt to figure out whether Carl 0:03:42.720 --> 0:03:48.200 Linneus was correct in categorizing the classes Amphibia and reptilia separately. 0:03:48.720 --> 0:03:52.520 It was a big question in those days. Covie incorrectly 0:03:52.600 --> 0:03:56.400 concluded the oxelotles, because they breathe through gills their entire lives, 0:03:56.800 --> 0:03:59.160 must be some sort of lizard that existed as a 0:03:59.160 --> 0:04:03.040 perpetual law va, in the words of paleontologists Stephen Jay 0:04:03.120 --> 0:04:08.880 Gold quote a sexually mature tadpole. Couvy was correct sometimes, 0:04:08.880 --> 0:04:14.360 but not in this case. And because oxeltles did incredibly 0:04:14.360 --> 0:04:18.479 well in laboratory and aquarium settings, a nineteenth century zoologist 0:04:18.520 --> 0:04:21.280 took it upon himself to provide every lab in Europe 0:04:21.320 --> 0:04:24.479 with a supply of them, which resulted in some truly 0:04:24.560 --> 0:04:27.400 horrific studies in which scientists chopped them up just to 0:04:27.480 --> 0:04:32.760 test the limits of their regenerative powers. Gardner said, these days, 0:04:32.760 --> 0:04:37.440 oxyletles are hugely important model systems for our studies about regeneration. 0:04:38.040 --> 0:04:41.120 We've known for decades, centuries even that we can remove 0:04:41.240 --> 0:04:44.320 parts of a developing embryonic structure and the cells that 0:04:44.360 --> 0:04:48.120 are left behind will fill in, repair, and regenerate that structure. 0:04:48.920 --> 0:04:52.320 But in most animals and mammals, for instance, the system 0:04:52.440 --> 0:04:55.120 sort of shuts down at the end of embryonic development. 0:04:55.760 --> 0:04:58.479 Salamanders seem to be able to revert back to that 0:04:58.640 --> 0:05:03.719 embryonic like state, re accessing the developmental program that's already there. 0:05:04.520 --> 0:05:07.200 Humans have the program, we just stop being able to 0:05:07.240 --> 0:05:10.359 access it when we're no longer an embryo. You could say, we, 0:05:10.839 --> 0:05:14.640 like oxylottles, have evolved the ability to regenerate just fine, 0:05:15.040 --> 0:05:21.320 but we've also evolved a mechanism that inhibits that. Oxeltles 0:05:21.400 --> 0:05:24.120 can endure a lot, but they have not been able 0:05:24.160 --> 0:05:28.039 to endure their home ecosystem, being overrun with introduced predators 0:05:28.080 --> 0:05:32.040 and environmental toxins. The lakes in their home around ultra 0:05:32.200 --> 0:05:35.839 urbanized Mexico City have become not only polluted by aging 0:05:35.880 --> 0:05:40.680 wastewater systems, but overrun by introduced telapia and perch, both 0:05:40.680 --> 0:05:46.200 of which view oxylottles as a delicious snack. Scientists counted 0:05:46.240 --> 0:05:50.600 around six thousand oxeltals per square kilometer in Lake Zotomilco, 0:05:50.800 --> 0:05:53.919 but these days fewer than thirty five animals take up 0:05:53.920 --> 0:05:57.200 the same amount of space. It looks like the oxylottle 0:05:57.320 --> 0:05:59.800 is on the fast track to extinction even in their 0:05:59.800 --> 0:06:03.680 home environment, which is something of a paradox like the 0:06:03.720 --> 0:06:09.159 oxelottle itself. While wild oxelttles are critically endangered, they're doing 0:06:09.200 --> 0:06:13.159 great in captivity. They're the most widely distributed amphibian in 0:06:13.200 --> 0:06:16.440 the world. Millions of them live in labs around the globe, 0:06:16.880 --> 0:06:19.320 many more in fact, than live in the wild now, 0:06:20.080 --> 0:06:23.160 and while they're important in science, they're also quite popular 0:06:23.320 --> 0:06:31.200 in pet shops. Today's episode was written by Jesslin Shields 0:06:31.200 --> 0:06:33.320 and produced by Tyler Clang. For more on this and 0:06:33.400 --> 0:06:36.760 lots of other regenerative topics, visit how stuff works dot com. 0:06:36.880 --> 0:06:39.560 Brain Stuff is production of iHeart Radio or more podcasts. 0:06:39.640 --> 0:06:42.359 My Heart Radio visit the iHeart Radio app, Apple Podcasts, 0:06:42.440 --> 0:06:44.120 or wherever you listen to your favorite shows.