The Insane Biology of: The Axolotl

in aztec mythology the legend of the five sons is the creation myth of our world the dawning of the fifth son brought about the era in which humans were created and is the era in which we currently live according to the myth this sun was created by the gods but was not able to move across the sky that is not without the nourishment of sacrifice the gods themselves were the first to be sacrificed to the sun setting the tradition of human sacrifice that the aztecs would later follow the god shalottal however did not want to be sacrificed to evade detection he changed himself into other forms first the maize plant then the agave plant and finally the water monster the axolotl when he was found his brother ketzel koat spared his life but banished him to live forever in darkness as an axolotl today this water monster is believed to still hold the spirit of a god axolotls are a type of salamander found only in the area of lake sochi milko outside mexico city near the ancient capital of the aztecs tenochtitlan and beyond their spiritual ties axolotls are unlike any other salamander they live permanently in the water and in fact live permanently in their juvenile form never maturing into their adult body a forever tadpole and on top of its age-defying ability the axolotl can regenerate almost any part of its body from missing limbs tails organs parts of the eye and even parts of its brain for hundreds of years the axolotl has been central to our understanding of how our own organs develop and function its unique physiology holding the answers to many of our most pressing biological questions and now we hope to crack the code of its regenerating superpowers to one day be able to harness them for ourselves but with only a few hundred kilometers of waterways that remain of its natural habitat the axolotl is on the brink of total annihilation in the wild and the time to unlock these mysteries is running out why is the axolotl so different from every other vertebrate what is it exactly about their very unusual physiology that makes them the most important amphibian known to science [Music] axolotls are members of the tiger salamander species complex and they evolved relatively recently compared to other salamander species in the region they grow to be about 23 centimeters long and come in a variety of colors and unlike almost all other salamanders they are neotenic meaning that they keep juvenile characteristics into adulthood they never undergo metamorphosis for them this means they remain aquatic never venturing onto land they keep their external feathery gills and tail fins and they lack movable eyelids when they were first shipped from mexico to prominent french zoologist augusta dumaril in the 1860s he was certain that the axolotls were the larvae of an unknown type of salamander that is until six months later when his specimens very unexpectedly reproduced and because the adult stage of animals is defined by sexual maturity these reproducing axolotls had to be adults just how strange the axolotl is was only beginning to be revealed overall retaining juvenile traits seems like a cute but weird thing to happen in nature at first glance it looks like a whole species that's had its growth permanently stunted but although axolotls are one of the only salamanders to stay in their juvenile form other salamanders from the region can sometimes be found doing the same thing with some individuals staying in the water for their whole lives at first naturalists didn't know what to make of this phenomenon but looking at where these salamanders lived started to give a clue as to why this may be selected for in nature all of the mexican lakes where they are found have a few key things in common first they are all large relatively permanent bodies of water at least they used to be before human intervention second the lakes are surrounded by desert and in many cases are the only permanent body of water in the region and third all of these lakes historically did not have any large predatory fish the salamanders in these lakes sometimes or always fail to mature into adulthood because these lakes are the only suitable habitat in the midst of a harsh and dry terrestrial environment salamanders normally metamorphose to take advantage of both water and land but only if the land is somewhat damp but staying in the water forever is a strategy that only works with no major predators lurking beneath the surface along with certain ph temperature and altitude requirements these mexican lakes just happen to completely fit the bill giving the salamanders a unique ability to thrive there for a while it was thought that the axolotl always fails to undergo metamorphosis that its neoteny is a permanent feature of its biology while this may be true most of the time it isn't true all of the time as french zoologist dumarill learned in 1865 when he was given an even bigger surprise from his axolotl specimens to his shock some of the individuals in his care transformed into their adult land-living form they looked sort of like tiger salamanders but different enough to still be considered their own unique species dumaril searched the rest of his life for an explanation of why these axolotls transformed but died before he ever got the answer but in the early 1900s the transformation of the axolotl again came to the front of research interests during this time researchers were narrowing in on thyroid gland tissue as a mechanism for amphibian metamorphosis and the axolotl was the most suited animal to clearly demonstrate its effect when axolotls were fed thyroid tissue from livestock the axolotls would metamorphose losing their external gills shedding their larval skin and venturing onto land basically thyroid tissue is a real-life moonstone for the axolotl in other instances axolotls can transform when forced to breathe air but this is stressful on the animal and takes much longer however it may be why some in captivity have unexpectedly metamorphosed the discovery of transforming axolotls played a central role in the road to our understanding of thyroid hormones like thyroxine which was first isolated in 1915 and synthesized in 1926. this marked the beginning of what would become the axolotl's immense contribution to medical research all organisms have some level of regenerative abilities for some animals regeneration is just a part of life flatworms and hydras can regenerate their whole bodies even from a tiny piece of their original selves starfish octopuses or even crabs can lose an arm and grow it back without much of a problem but these animals all share something in common they're all invertebrates in vertebrates like us regeneration is pretty much limited to regrowing skin or scar tissue over a wound except for our liver we can't regrow our organs nor our limbs in fact almost no vertebrate can regenerate much beyond what we can that is except for the axolotl and the other members of the salamander order the only other vertebrates that can regrow limbs are frogs but frogs lose the ability once they fully turn into their adult form the axolotl retains its regeneration ability throughout its entire life the way an axolotl regrows a limb begins with the limbs surviving cells once the limb has been severed or lost a blood clot rapidly stops the bleeding at the cut and a layer of cells covers the area of amputation this part is not so different from the way we would heal then over the next few days the cells underneath the epidermis begin to rapidly divide forming a cone-shaped structure known as a blastoma also called the regeneration bud the blastoma is what holds the key to regeneration it's where regular bone cartilage or muscle cells de-differentiate meaning they lose their identity and transform back into stem cells slowly they start reforming bone skin and veins much like stem cells would do when the animal is first developing in its egg as the cells in the blastoma continue to divide nerves and blood vessels connect it to the rest of the body the limb eventually grows back completely looking like an exact copy of the limb that was lost and while total limb regeneration is impressive enough axolotls are also capable of something that seems like it should be downright impossible regrowing parts of their brain in mammals like us and in fact most vertebrates neurons typically only grow in the embryonic stage any neurogenesis that happens in adulthood is quite limited if the brain is damaged in adulthood it usually can't regenerate new neurons blood vessels or tissue yet somehow doing this is no problem for the axolotl by de-differentiating stem cells they can add new neurons throughout their life and can regenerate the spinal cord and parts of the brain after an injury salamanders are the only four-legged vertebrates that can transform regular cells back into stem cells allowing them to redevelop into new tissue this may seem like a superpower but the axolotl doesn't actually have special regeneration genes to do this they are simply regulating their genes differently from other animals this fact gives scientists hope that we may have this ability still locked within us an ability that if unlocked could greatly benefit people suffering from certain organ failures amputation of a limb or serious burns while we still don't know the exact mechanisms that allow the axolotl to de-differentiate cells some of the key components are starting to be unveiled many of them resembling the cells and molecules that are already at work in our bodies one way to learn what molecules and cells are necessary for an axolotl to regenerate is to look for molecular tweaks that cause them to lose their regenerative ability for example macrophages are known to be critical during inflammation in response to an injury in many animals and have previously been connected to regeneration and so researchers found that injecting a drug that eliminates the macrophages in an axolotl's limb before amputation causes it to form scar tissue instead of regenerate this shows that macrophages a type of cell we readily have are an important component for regeneration researchers similarly found that a protein called transforming growth factor beta is key in axolotl regeneration a molecule that is also essential in preventing scar tissue in injured human embryos during the first trimester and on top of this researchers have also found that both mice and humans can regenerate a partially amputated finger or toe though humans lose this ability as they get older researchers believe that this is due to a type of stem cell that lies beneath the fingernail that normally helps the fingernails to perpetually grow they now think that these cells could also be a remnant from a time when our regeneration abilities were stronger the regrowth of the mice digits studied depends on two certain types of proteins called wnt and fgf2 proteins and certain signaling pathways proteins and pathways that all seem to be the same as those in salamanders during regeneration all of this suggests that we may partially retain the same regeneration abilities as the axolotl abilities that could one day be reawakened for this reason the axolotl is one of the most incredible and most important research animals in science along with becoming a beloved pet in freshwater aquariums worldwide and yet they are facing almost complete annihilation in the wild the conservation story of the axolotl is a unique one and if we're not careful we risk losing one of the most incredible creatures on earth the wild axolotl is teetering on the brink of extinction their population has exponentially declined in the last few decades in a 1998 survey it was reported that around 6 000 individuals lived per square kilometer in their habitat in 2015 just 35 individuals were found per square kilometer they were predicted to go extinct in the wild in 2020 though they have just barely escaped this fate no one knows exactly how many are left now but the numbers are dire today the axolotl is found naturally in only one place like sochi milko but the modern diversion of this lake is more like a series of small canals it's a phantom of what it used to be representing only two percent of the original massive wetland system centuries ago this area contained several great lakes which were home to many mesoamerican cultures including the teotihuacanos the toltecs and later the aztecs at the time of the spanish conquest in 1519 the size of these lakes would have covered much of modern day mexico city due to its naturally shallow waters and its freshwater springs in the south lake sochi milko was the center of chinampa agriculture in the centuries before the spanish arrived these artificial islands created an extensive network of canals the ancient cities here in a way looked a lot like the venice of today here the axolotl thrived alongside humans but over time the population of the area grew and grew and eventually the lakes were all drained with the exception of lake sochi milko to prevent flooding and to allow urban expansion what remains of lake sochi milko today is highly polluted full of dangerous algae blooms and invasive large fish which both out compete and eat the axolotls it's no surprise that the axolotl is almost gone there and yet in labs around the world the axolotl is abundant they've even been called the white mice of amphibians since they are ideal for research and are easy to rear in the lab they are the most distributed amphibian in the world so you may ask the question if the axolotl is thriving in aquariums and labs what's the issue unfortunately the lab colonies are not staying healthy these captive populations are becoming inbred lacking the genetic diversity that wards off disease to help mitigate this scientists have crossbred the axolotls in captivity with the similar species the tiger salamander but this has left many lab specimens with a host of foreign genes meaning that they aren't quite the same as wild axolotls anymore one proposed solution to the decline of wild axolotls is to simply reintroduce some of the captive population back into their natural habitat but until the lake is cleaned up putting them back would be a death sentence and despite the efforts of some scientists and conservationists like sochi milko becoming clean and healthy anytime soon seems unlikely instead of reintroducing them into their original habitat some scientists have a different idea to give the axolotls a new home one suitable site has been identified near mexico's national autonomous university a freshwater lake has been born out of an abandoned quarry and researchers are now using it as an ecological research site dozens of axolotls have been released here and are tracked using radio transmitters eventually these research subjects are expected to breed here and a new type of semi-wild population may be born perhaps with the introduction of wild caught axolotls along with the lab-reared ones genetic diversity could improve and even though it's a different ecosystem than the swampy canals that they evolved in places like this may be the best option for the long-term survival of these magnificent creatures mexico is one of the most bio-diverse countries in the world it sits with brazil colombia and indonesia at the very top of the biodiversity list with thousands of unique endemic species it's estimated that more than 10 of all of the world's species live in mexico for this reason it's considered to be a mega diverse country the axolotl is far from the only notable native species that mexico has to offer the mexican prairie dog burrowing owls the mexican wolf the rarest subspecies of wolf in north america and the american bison the largest land animal in the americas are all amazing creatures that live in the grasslands of mexico grasslands an ecosystem that may be easy to overlook are in fact teeming with biodiversity the number of different types of grasses there is comparable to the number of different types of trees in a tropical rainforest i personally didn't know much about this incredible ecosystem before watching my wild backyard on curiosity stream the janos biosphere reserve episode grabbed my attention especially since i live in texas and this ecosystem is truly in my backyard other episodes explore the unexpected wildlife of new york city or the stunning national parks of argentina it follows local ecologists and scientists as they show us the hidden wonders of wildlife that exist all around us curiosity stream is a streaming platform with thousands of high quality documentaries like this one and now curiositystream is partnered with us to offer an incredible deal by signing up to curiositystream you now also get a subscription to nebula nebula is a streaming platform made by me and several other educational youtube content creators it's a place where we can upload our videos ad free and a 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engine [Music]

Channel: Real Science

Views: 2,535,339

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Id: bFkIG9S2Mmg

Length: 21min 2sec (1262 seconds)

Published: Sat Oct 16 2021

Reddit Comments

[u/BuddhistSagan]

This channel is underrated

[u/Wonderful-Thing8385]

Don’t know if the Axolotl still exists in Blue Lake in Montana but we U of M students had tried to save them back the 80s.

[u/Sindrelf]

Never knew about the mythological significance of Axolotls. That's so cool!