What is an Axolotl? A Fish? A Salamander? And Why It’s Confusing

Written by Hailey Pruett
Published: February 3, 2022
Image Credit Spok83/Shutterstock.com
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One of the most bizarre members of the Amphibia class is the axolotl. This strange animal looks more like a fish from science fiction than an actual amphibian! Native to just a few lakes in Mexico City, their numbers in the wild are diminishing due to habitat loss, but their popularity in the pet trade has helped offset this somewhat. Nowadays, they’re fairly common pets and well-loved by herpetology enthusiasts everywhere.

At this point, you’re probably asking: what even is an axolotl, anyway? Why they’ve evolved to look and behave so differently than the frogs and other salamanders they’re related to? Well, it’s actually a bit complicated. To clear things up, let’s take an in-depth look at how we classify these unique creatures.

Are Axolotls Fish, Salamanders, or Something Else?

golden albino axolotl
Even though they look like otherworldly fish, axolotls are actually just aquatic salamanders.

iStock.com/Trebor Eckscher

Axolotls are fully aquatic salamanders. They are currently part of the Ambystomatidae family within the order Urodela. This includes medium-sized salamanders such as the tiger salamander. Axolotls are notable as amphibians as they never undergo metamorphosis but rather stay in their “juvenile” form and retain their gills their entire lives.

While they do look a lot like fish, axolotls are actually far from it! They are, in fact, amphibians, along with frogs, salamanders, newts, olms, and caecilians. However, while most salamanders and other amphibians trade their gills for lungs upon reaching adulthood, axolotls never lose the feather boa-like gills around their necks. This unique state in which juvenile traits are retained throughout an animal’s life is known as neoteny.

Interestingly, axolotls do have functioning lungs in addition to their gills! They’re actually able to breathe using all three of their external gill stalks, lungs, and skin. They’re very efficient at absorbing oxygen from water, but they cannot breathe on land and must stay submerged for life.

Why Don’t Salamanders Undergo Metamorphosis?

blue speckled axolotl
Axolotls retain their external gills for their entire lives.

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Axolotls don’t (typically) morph into salamanders because the water they live in lacks sufficient iodine. Crucially, iodine triggers the axolotl’s body to produce thyroxine, or T4, a thyroid hormone that jumpstarts the morphing process. It is possible to force axolotls to undergo metamorphosis via iodine or thyroxine injections, but this is risky, painful, and very stressful for them.

It turns out, the few bodies of water axolotls are native to don’t contain enough iodine to facilitate metamorphosis. Because of this, they simply remain in their “juvenile” state their entire lives, retaining their external gills the whole time.

In captivity, however, it is technically possible to force them to morph into salamanders. Some experienced exotic pet owners and researchers have been able to do this successfully by injecting their axolotls with iodine or thyroxine. This process, however, is largely regarded by herpetology enthusiasts as unnecessarily cruel. In addition to causing the axolotl a significant amount of trauma and stress, morphing can injure or kill them.

It is also important to note that purposely morphing an axolotl into a salamander does not extend their lifespan or improve their quality of life in any significant way. It merely changes their appearance and the primary method they use to absorb oxygen.

Can Axolotls Regrow Their Limbs?

white albino axolotl
Axolotls can regenerate lost or damaged limbs with ease.

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Like the salamanders and newts they are related to, axolotls are extremely efficient at regenerating damaged or severed body parts. Not only can they regenerate limbs, but they can also regrow damaged heart, brain, and lung tissue! They are even able to regenerate parts of their spinal cords after serious injuries.

The secret to axolotls’ regenerative abilities has long confounded researchers, but we’re learning more about it every day. Currently, herpetologists believe axolotls’ skin and other nearby cells gather around the severed limb or damaged body part and form a mass called a blastema. Next, the cells rapidly diversify and develop into the specific types of cells the axolotl needs to regrow the limb or tissue.

Beyond this knowledge, though, scientists are still stumped as to what exact part of the axolotl’s genome is responsible for the regeneration. Hopefully, in the future, the mystery will be solved, as the ability to regrow limbs and tissue will be incredibly valuable for medical research on humans and other animals.

Can You Keep Axolotls As Pets?

leucistic axolotl
Axolotls have become common exotic pets in recent years.

Meggyn Pomerleau/Shutterstock.com

Currently, axolotls in the wild are critically endangered according to the IUCN. However, exotic pet breeders have greatly increased their numbers in captivity. As a result, they are now available for purchase from various sellers for as low as $20 to $50. In general, axolotls are relatively easy to keep as pets. They thrive in cool water and can live in modestly sized aquariums. Besides, they require little more than substrate, frequent water changes, and a few hiding spots for privacy.  

However, while the overall cost of an axolotl’s care is very manageable, they do not tolerate handling. Additionally, their highly sensitive skin is prone to damage and infection if their water temperature, pH level, or quality is not ideal.

Surprisingly, axolotls have become popular pets in the past few decades! This is mostly thanks to their cute appearance, fascinating biology, and fairly minimal care requirements. 

Axolotls have very mild-mannered, curious temperaments, which makes them a delight to observe in captivity. Plus, they can live for over 15 years with high-quality care, making them great long-term pets to bond with. The cost of their food is also low, as they primarily feed on brine shrimp, water fleas, and worms.

Unfortunately, although they are very cute, you should never handle an axolotl directly. Despite being hardy animals overall, their skin is extremely sensitive to fluctuations in their environment. They cannot breathe unless their skin stays moist, so you can’t remove them from their enclosures for long. If you’re looking for a pet that you can cuddle up with, an axolotl isn’t a good choice.

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About the Author

Hailey Pruett is a freelance content writer, editor, and lifelong animal lover living in Tennessee with their spoiled cat, grumpy leopard gecko, and loving partner. Their favorite animals are lizards, turtles, snakes, and frogs. When they aren't obsessively writing about how awesome reptiles and amphibians are, Hailey is usually playing relaxing life simulator video games and obscure, old-school RPGs. They are non-binary and comfortable with any pronouns.