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January 23, 2024 10 mins

These adorable aquatic salamanders are voracious hunters -- and have myth-like powers of regeneration. Learn more about the axolotl in this episode of BrainStuff, based on this article: https://animals.howstuffworks.com/endangered-species/axolotl.htm

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Speaker 1 (00:01):
Welcome to Brainstuff, a production of iHeartRadio. Hey brain Stuff.
Lauren Vogelbaum. Here today we're talking about axe lottles, a
threatened species of large salamander that live in fresh water,
and they're not actually fish at all. Despite sometimes being
called Mexican walking fish. With their round heads and permanently

(00:23):
smiling faces, wild axe lottles are cute. It's one of
the reasons they do well with pet owners in the
pet trade. One reason they're cute is because they display niatny,
which means they retain a lot of their juvenile features
throughout their adult life, beyond their faces. Although adult axe
lottles also have functional lungs like other salamander species and

(00:46):
can breathe through their skin, they also have big, fluffy,
feathery external gills, something most amphibians don't keep after babyhood.
They have small, delicate, webbed feet and a long tadpole
like tail crusted with a translucent fin. Because they don't
have to rely on their webbed feet and legs for
land travel, but they do have to be able to

(01:07):
move through water like a big tadpole. In the wild,
they're most often dark brown, gray or black, with lighter speckles,
but deepigmented variants with gold skin and eyes or pink
skin and red gills are common, and you often see
them as pets as scientists think that they stay baby
like throughout their lifespans because, unlike other salamondar species, the

(01:28):
wild ax lottl population evolved in very stable habitats. In
most other salamonder species, such as the tiger salamander, live
in wetlands that dry up during certain parts of the year,
so they have to get rid of their feathery gills
and breathe through functional lungs and through their skin. A
wild ax lottles evolved in a habitat with year round

(01:49):
water and with very few aquatic predators, so they don't
need to spend energy changing their bodies to suit their
changing circumstances. An x lottle's life span is about fifteen
years in captivity, but a wild x lottle probably lives
only five or six years. They reach sexual maturity at
one year, and though they are solitary creatures for the

(02:10):
most part, in February, breeding season begins and wild ax
lottle males begin finding females using pheromones. When they get together,
he does a courtship dance in which he shakes his
tail in her direction. After the female acquiesces to his attentions,
she pokes him with her nose and he deposits a
sperm packet on the lake floor, which he picks up
and uses to fertilize her eggs. The wild, female ex

(02:33):
lottle will lay hundreds of eggs in the weeds or
around some rocks, and then leave them to fen for themselves.
Baby x lottles receive zero parental care. In fact, young
axe lottels, hungry after hatching from their eggs, have been
observed gnawing on their siblings legs and pails for sustenance,
though as you'll see, this is totally fine because the

(02:54):
legs will just grow back in their home ecosystem. Axe
lottles are or at least used to be top predators
around the lakes, wetlands, and canals of Central Mexico, where
they originated and once thrived. Although they appear unassuming, they're
actually ruthless carnivores, feasting on worms, mollusks, insects and insect larvae,

(03:16):
and even small fish. In the wild, they'll also eat
pretty much any animal that you put in a tank
with them. Post ancient Mesoamerican cultures used the axe lottle
as a source of food and medicine, Some said a
gift from the gods. A Myths from that area associate
the animal with an underworld god, Sholat, who in some
legends escapes capture by turning himself into a small, feathery amphibian.

(03:41):
His name comes from the Nawat language and is spelled
the same as axe lottle without the letter A at
the front, but European language speakers didn't pick up the
pronunciation when they picked up the animal. A part of
the mythology of the axe lottl centers around the fact that,
alike a powerful god, they are difficult to kill. If
an ox lottl loses virtually any part of its body,

(04:03):
it can regenerate it no problem a. While sub lizards
can grow back a tail bisected, flatworms can grow back
the other half, and starfish can regrow a limb, an
ax lottle can regrow practically any part of its body
in a few weeks. For the article this episode is
based on How Stuff Works. Spoke with David Gardner, a

(04:23):
professor in the school of Biological Sciences at the University
of California, Irvine. Back in twenty nineteen, he said, of
the animals that are closest to us the vertebrates, salamanders
are the only ones that can regenerate in this way
and can heal without scars. Other salamanders can regenerate, but
axe lottls do it best. When the Europeans got wind

(04:46):
of axe lottal regeneration, ax lottls went from being a
sort of boring exhibit in a zoo to one of
the most important and longest self sustaining lab animals in history.
Among the first modern zoo animals, thirty four ax lottls
are brought from Mexico, along with three deer and three
wild dogs, to Paris in eighteen sixty four, and although

(05:06):
they weren't as interesting to nineteenth century zoogoers as the larger,
more charismatic animals, scientists quickly realized that these unassuming little
guys were strange, almost mythological in fact, and they were
studied at the time for their unusual adult form and
their regenerative abilities. A Gardner said, these days, ax lottls

(05:27):
are hugely important model systems for our studies about regeneration.
We've known for decades, centuries even that we can remove
parts of a developing embryonic structure and the cells that
are left behind will fill in, repair and regenerate that structure.
But in most animals mammals, for instance, the system sort
of shuts down at the end of embryonic development. Axe

(05:49):
Lottels and other salamanders seem to be able to revert
back to that embryonic like state, reaccessing the developmental program
that's already there. Humans have the program, we just stop
being able to access it when we're no longer an embryo.
You could say, we, like axe lottels, have evolved the
ability to regenerate just fine, but we've also evolved a

(06:10):
mechanism that inhibits that. Scientists hope to figure out how
to one day apply the axe lottl's regeneration abilities to
the human body. They can regenerate new limbs, heart tissue, eyes,
and even its spinal cord in parts of their brain,
and make new neurons throughout their lives, which human brains
do too, though not as readily. It is possible to

(06:35):
force anax lottel to metamorphin into an adult salamander without
gills by injecting it with iodine or thyroxine, or by
feeding it foods that are rich in iodine. However, scientists
have found that afterward they don't easily regenerate cells, and
for all their seeming magic, wild ax lottls are critically

(06:55):
endangered today. The waterways in their home around Mexico City
have become not only polluted by aging wastewater systems, but
overrun by introduced telapia and perch, both of which view
ax lottles as a delicious snack. In twenty nineteen, a
population assessment concluded that there are probably fewer than one
thousand individuals left in the wild. The Mexican government and

(07:19):
many conservation groups are doing their best to save the
species by restoring the lakes and natural habitats they live in.
One strategy is to make stationary floating island habitats for them,
called danumpas a Spanish word for rafts made of aquatic vegetation, mud,
and wood that were used hundreds of years ago as
floating gardens before Spanish colonizers arrived. When what's now part

(07:43):
of Mexico City was the Triple Alliance City, state of
tinoche Titlan. The Empire built and farmed on a vast
network of chanampas for miles around the city. This system
of agriculture created canals that were shallow and sheltered, and
where the ox lottl popular thrived. When the Spanish conquered
the city, they remove the chumpus and drained the canals

(08:05):
and lakes. Today, the natural habitat of the wild oxilotl
population is limited to the southern part of Mexico City.
People are working to remove the invasive fishes that eat
the axe lottls and begin using jenumpus again, which not
only provides habitat for the axe lottles, it also filters
toxins out of the lake water. Ecotourism of these danumpus

(08:29):
has assisted in funding axe loottal conservation efforts. Meanwhile, captive
populations axe lottls are doing great. They're the most widely
distributed amphibian in the world, and because scientists desperately want
to figure out how to help you regenerate a new
set of toes, millions of them live in labs around
the globe. And while axe lottle research is important in

(08:52):
science and captive populations of pet axe lottls are also popular.
It's not legal everywhere for pet owners to keep ax lottles,
so it's important to check your local exotic pet laws
before you go looking for one and mess with any
living creature. Be sure to read up on how to
care for one before you take the dive. No pun intended.

(09:13):
They're not difficult to keep per se, but speaking as
a home aquarium enthusiast myself, I can tell you that
keeping any aquatic life form comfortable in your non aquatic
home can take a lot of work. Today's episode is
based on the article the super cute axe Lottle is

(09:34):
also a ruthless carnivore on HowStuffWorks dot Com, written by Jesslinshields.
Brain Stuff is production of iHeartRadio in partnership with how
stuffworks dot Com and is produced by Tyler Klang. Perform
more podcasts from my heart Radio, visit the iHeartRadio app,
Apple Podcasts, or wherever you listen to your favorite shows.

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