Axolotl age determination

Do Axolotls Never Grow Up? The Truth About Aging in Axies

Do Axolotls Never Grow Up? The Truth About Aging in Axies

This post is to address a question that comes up sometimes that people are curious about.

Do axolotls grow up, or not?

Is it true that the stay babies forever until they die?

Do Axolotls Never Grow Up?

The answer is yes... and no.

What is considered the final adult form for most salamanders is the morphed salamander - one that ultimately goes on land.

Axolotl's don't normally morph.

They stay in their larval stage.

So in that sense, they don't reach their final form.

Axolotls remain in a juvenile state their entire lives.

Key word: STATE.

They are neotenic, which is a fancy word that means the adults retain juvenile characteristics through their entire lives. Such characteristics include feathery gills, a tadpole-like dorsal fin and thinner legs.

But technically, and contrary to some thinking, axolotls don't stay babies.

They do reach adulthood though through regular aging, and attain sexual maturity  - just in the outward form of a juvenile.

Being perpetually in a juvenile state gives them several advantages:

  • They heal without scarring
  • They can remain in water, avoiding land predators
  • Their immune systems are stronger
  • They require less food
  • They retain their adorable floofs (well, an advantage to us axie lovers :) )

They still age though.

That's why they don't live forever - and why they can still have babies.

This is unusual from most species of mole salamanders, as part of their typical life cycle involves absorbing their gills, growing eyelids and coming out on land (morphing), losing their fully aquatic nature.

Once a salamander morphs, it loses its amazing regenerative abilities (along with its juvenile features) and becomes a true adult in its outward physical form.

There are some other drawbacks too...

  • They demand more food.
  • Also, their lifespan is considerably shortened.
  • They require more oxygen and can't survive in water only.


Morphing into a fully adult salamander requires a HUGE amount of energy for the axolotl to perform.

It can be a dangerous process if they don't have the proper environment to morph in.

Among some species of salamanders, neotony is more prevalent in cold mountain streams and lakes without access to much iodine (more on that later) and with little food.

That jives with the axolotl's native lake habitat.

Axies do have a pair of lungs that they use to breathe occasionally, they just don't fully rely on them like morphed salamanders do.

They are basically tadpoles, except that besides the external gills they have fully formed hands and feet.

Related Post: Fun Facts About Axolotls

Metamorphosis: What it Is

It might be useful to equate the axolotl to other species that live in stages.

For example, insects like butterflies and moths, and other amphibians like frogs and toads.

With insects, metamorphosis is triggered by reducing amounts of something called juvenile hormone.

The creature is born with quite a bit of it. When it drops, that triggers the big change.

It's the opposite with axolotls.

Axolotls are triggered to undergo metamorphosis by a thyroid hormone called "thyroxine."

When this hormone builds up to strong enough levels, the animal is triggered to change into its final form.

The buildup of this hormone in axolotls causes them to trade their baby-like characteristics for adult ones - losing gills, growing eyelids and more.


With axolotls, either they never get that surge of thyroxine...

... Or they don't have enough receptors to react to that hormone to trigger morphing.

This is interesting:

With axolotls, the development of reproductive organs seems to operate outside of hormones that normally change the animal into an adult.

So they can still grow up (yes, grow up, just not morph) to have offspring - despite looking like a larvae.

Did Wild Axolotls Naturally Grow Up (to Morphing)?

There are conflicting ideas about this.

Without being able to study the animals now, we are left to some level of speculation.

One line of thinking among some axolotl breeders is that among the native wild axolotl (now extinct) populations, morphing was far more common than it is among our pet Mexican walking fish.

The reason being, is that domesticated axolotls we have now are much different to what used to live in the wild due to selective breeding.

Historic accounts indicate that morphing among their axolotls was surprisingly quite common, apparently much more so than it is today.

Over the last hundred years or so, axolotl breeders have gradually eliminated the majority animals that morph from their breeding stock, mostly out of necessity, as breeding the morphed animal is generally more difficult.

But some effort has been intentional, because most people prefer an axolotl pet that stays fully aquatic.

That said:

Axolotls (rarely) do morph and become terrestrial adults.

This may be due in part to the fact that they have been hybridized with species of tiger salamander to create albino genes.

And tiger salamanders consistently morph.

Morphing among axolotls can be genetic and unavoidable in some cases, but it can also be induced.

The administration of iodine (ingestion or injection) can trigger morphing by creating hormonal changes in the axolotl's brain (producing thyroxin).

If you want your axie to stay in its tank where it belongs?

Here's a tip:

Be careful to avoid feeding foods that contain iodine or using salt baths of iodized salt!

Why Aren't Axolotls Immortal?

This begs the question for some:

If axolotls never progress past their larval form, why do they die of old age?

Well, just because something doesn't reach its final form doesn't mean it can't age and damage occur to cells over time.

Axolotls still age...

It's just not nearly as rapid as morphed adults.

That's why they can still have babies.

They aren't technically babies and they do grow up.

For them, adulthood is still in a larval phase.


Yep, it's pretty amazing how, despite being baby-like, your axolotl can still have babies and be an adult.

I hope you learned something new in today's post!

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