Axolotls have the strongest regeneration factor among vertebrae. They are fascinating creatures. If you’re looking to learn more about the phenomenal abilities Axolotls possess, you’re in the right place.
How does the amazing phenomenon of axolotl regeneration actually work? Axolotls can regenerate their limbs, heal their own spinal damage, and attach body parts from other Axolotls. All of this is done through the cells of the wounded area, which quickly convert into undifferentiated cells. These cells can then expand into the correct shape. Eventually, they convert back into the needed cells.
It’s a lot to take in, but Axolotls are incredibly complicated creatures that have been mystifying scientists for years now. Axolotl regeneration has many facets.
I’ll focus on these facets in the below sections, including the basics, the limits, splicing and attaching, and where current studies of this animal are leading.
The Basics of Axolotl Regeneration
At the spot of amputation, clotted blood cells prevent the axolotl from losing too much blood. Within a few hours, the wound is covered by epidermal cells which come from around the wound. These epidermal cells multiply, forming a sort of stump on the injured area. This proliferation of cells forms a wound epidermis.
A wound epidermis is genetically different than a normal set of epidermal cells, as cells in the normal epidermis of axolotls are a lot more differentiated than cells in a wound epidermis.
The undifferentiated nature of these cells is what later allows the cells to turn into the perfect replicas of the lost limbs.
Over the next few days, the cells on the wound begin to grow and multiply. This is followed by the cells under the skin growing and multiplying. The result is a cone-shaped collection of cells called a blastema. The cells in the blastema seem to come from different cell types within the axolotl’s body.
These cells are still in a state of undifferentiation, which makes them similar to any stem cells in use. However, unlike stem cells, blastema cells are unable to form into just any cell. They can only convert back into the type of cell they were originally.
If the cell was originally a muscle cell and then transferred to an undifferentiated blastema cell, it could only turn back into a muscle cell.
The cells in the blastema, in their undifferentiated state, multiply again and slowly begin to convert back to the required specified cell type. As the blastema expands, it begins to flatten out and eventually stretches to a size that will perfectly match the Axolotl’s body.
Once regenerated, the axolotl’s new limb is indistinguishable from the limb which it lost. Even the blood vessels and nerves are perfectly in their proper places!
That’s a lot of information to break down for you, but the process is even more complicated than that. If you are interested in more details on exactly how the axolotl regenerates, check out this Harvard.edu post on the topic.
Axolotl Regeneration Abilities Compared to Others
When it comes to understanding just how great a feat an axolotl’s regeneration is, you first need to understand what some other animals are capable of.
Humans, for instance, can sometimes grow the tips of their fingers back when they are young. This isn’t very common and only applies in the early part of a person’s life.
Rats improve upon this ability slightly by having the capability to consistently regrow the tips of their fingers throughout their lives. Certain lizards can regrow their limbs and often their tail. Zebrafish are able to regrow only their tails, and newts are able to regrow their limbs.
However, the axolotl is the only vertebrae capable of regrowing its limbs throughout its entire life, seamlessly, and can even regenerate things like its spinal cord.
When it comes to regeneration, the axolotl does get beaten by sea creatures like the starfish, which can regenerate its whole central nervous core. The flatworm and the hydra are able to regenerate any parts of their bodies, as well, giving the axolotl a run for its money.
Lastly, the immortal jellyfish is so highly regenerative that it can prevent the decay of necrosis caused by age, so it’s probably the most regenerative creature out there.
So, why is the axolotl so special? There are better regenerative creatures out there, so why study the axolotl’s abilities?
Axolotls are the closest related creatures to humans which have such a high regenerative ability.
With their close relation to humans, they are choice animals that are being experimented on to find medical phenomenon to potentially transfer to humans.
Limits of Axolotl Regeneration
The time it takes for a limb to regenerate is based on several different factors. Mainly it comes down to the size of the limb, how old the creature is, and if it is the only limb being regrown.
A juvenile axolotl with a missing arm might take 40 to 50 days to regrow it. As the axolotl grows older, the limbs grow larger. This means it takes longer for the axolotl to regrow its limbs to the appropriate size.
How Many Times Can a Limb Regenerate?
As far as we can tell, axolotls can seemingly regenerate their limbs any number of times. Obviously, the Axolotl has a limited lifespan in years, so there would eventually have to be a finite number based purely on the axolotl getting too old to regenerate.
Otherwise, there doesn’t seem to be any limit to the number of times a limb can be regenerated by these creatures.
What Can an Axolotl Regenerate?
The list is pretty large, but to point out the most significant players an axolotl can regenerate, they are:
They can grow back almost anything.
“You can cut the spinal cord, crush it, remove a segment, and it will regenerate. You can cut the limbs at any level – the wrist, the elbow, the upper arm – and it will regenerate, and it’s perfect.
There is nothing missing, there’s no scarring on the skin at the site of amputation, every tissue is replaced. They can regenerate the same limb 50, 60, 100 times. And every time: perfect.”Professor Stephane Roy
of the University of Montreal
Splicing and Reattaching
If you aren’t already astounded by the axolotl’s regenerative abilities, this next section is sure to surprise you.
While it is possible for an axolotl to regenerate a limb, it’s also possible for it to graft in a limb! If they find a limb from another axolotl and connect their cell tissue to the newfound one, they can get an extra limb.
This is super weird and can result in an axolotl having an extra functioning arm. Granted, it’s not all that useful since it is sprouting from the same place as its original arm, but it is possible to have a load of extra limbs added to one axolotl.
This grows even more interesting. When you splice the arm of a neon-infused axolotl with an albino axolotl, the limb that grows in is the same color as the spliced arm. Meaning you can have an albino axolotl with a neon limb.
So it’s not just the axolotl reading another limb. It is somehow able to interact with the foreign cells near its wound and then recreate the arm which those cells were supposed to be.
If that hasn’t surprised you enough, then I have yet another curveball for you. It turns out that this doesn’t just apply to an axolotl’s limbs. In a study done in 1968, scientists transplanted a second head onto the back of an axolotl.
The heads weren’t fully functional, but quoting the study:
“In the best cases, the following movements could be observed: movement of the chin; movement of the gills; dorsoventral movement of the whole head accompanied by the retraction of the eyes; and complete opening of the mouth.” (Transplantation of Axolotl Heads)
It is these powers of regrowth that makes the axolotl such a hot topic in the scientific community, especially around the biological development departments.
Studying the Axolotl to Unlock Its Power
Imagine if we could harness the power that the axolotl has. Regrowing limbs, healing severe burns, even fighting off cancer… these are all possibilities. What steps are currently being taken to use the axolotl in research?
There is a lot that has to go into studying the axolotl before we can really adapt its powers to humans. The biggest of these projects in learning the genome of the Axolotl.
A genome is like a masterpiece guide to the DNA of a species. Back in April of 2003, we finished the human genome project. This measured the human genome, which revealed that humans have 3.3 billion base pairs in their DNA. That beneficial project was a megaproject that took the work of hundreds of countries.
Though we have only started studying the genome of the axolotl we know that this project is going to be massive. For one it has a massive genome filled with 32 billion base pairs in its DNA. That’s 10 times the amount humans have!
The start of the study of Axolotls’ genome has already released results, as there is strong evidence to support the idea that the immune system of an axolotl (specifically the Macrophages) is imperative to the regrowth of limbs.
This is so much the case that when a drug was applied to remove the macrophage from the axolotl, the affected limb didn’t regrow. Instead, it grew scar tissue.
One of the major fields that it is hoped that we can implement the things that we have learned from axolotls and their ability to regenerate is in lung trauma in humans.
Humans seem to have natural regenerative abilities in their lungs already. If they can be fully unlocked through the study of the axolotl add how it regenerates than we may be able to find methods to heal wounds and other injuries to the lungs.
These results are just the start of the journey to see where this powerful regenerative creature will lead us.
For more information on the Axolotl and it’s amazing regenerative abilities, check out the following video and links.
Advances in Decoding Axolotl Limb Regeneration
Salamander’s Genome Guards Secrets of Limb Regrowth
Axolotls Regenerate Without Getting Cancer
When we think of rapidly multiplying cells, it’s no surprise that cancer comes to mind. Cancer is just that, rapidly multiplying cells, so we thought that creatures like the axolotl would be at an increased risk of getting cancer from the rapid cell creation ability which they have.
That’s not the case, though.
“The interesting thing about salamanders is that even though they regenerate, they hardly ever get cancer. Whereas people, obviously, they get cancer all the time.”Jessica Whited Assistant Professor at the Harvard Medical School
To test this interesting phenomenon there was an experiment run in 1952 where researcher Charles Breedis inject several newts with coal and other known carcinogens.
Of the five hundred of these creatures tested only two grew tumors. It was more frequent for the newts to respond by growing another arm. Scientists are hoping to capture and control this ability and see if they can transfer it to other creatures like humans to provide the option of limb regrowth to amputees.
For more information on Axolotls and their seeming avoidance of cancer altogether, check out this quanta magazine article.
When a second limb is transplanted onto an axolotl, is it functional? The limbs of an axolotl can be functional when they are spliced into the axolotl. This does have some limits. When a second head was transplanted onto the back of another axolotl, it didn’t have the full functions of a head (though it was able to move its eyes and open its mouth).
Is the axolotl better at regenerating than other salamanders? It is a big misconception that axolotls are better at regenerating than salamanders are. The truth is, axolotls are just the easiest to test. They work so well in a lab environment that they are actually the oldest species to live in captivity, we are still studying them! They are pretty accustomed to tank life.
How did the axolotl become endangered? When you hear about the amazing regenerative powers of the axolotl, it is hard to conceive how there are only 700 to 1,200 of them alive today. What caused their demise? Unfortunately, many axolotls died due to the eradication of their home environment, when settlers like the Spanish colonized the axolotls’ hometowns in Mexico.