All About Axolotls: The Mexican Walking Fish

Leave a comment / / Updated on: 11th November 2023

NameAxolotlDietCarnivorous
Scientific nameAmbystoma mexicanumWeight300 grams (10.6 oz)
Pronunciationash-oh-lotLength15 to 45 cm (6 to 18 in)
ClassificationAmphibia, Urodela, & AmbystomatidaeLocationMexico

The Axolotl

axolotls
The mysterious axolotl | TatianaMironenko via Getty Images

If you’ve ever seen pictures of an adorable white aquatic salamander with noticeable external gills, that’s the axolotl!

This salamander is closely related to the tiger salamander and is, in fact, often mistaken for the larval form of the latter. 

That’s unsurprising, considering that axolotls do look like young tiger salamanders because they never actually metamorphose into an adult form!

Axolotls can reach physical adulthood, but they lack the most important ingredient! You’ll have to keep reading to discover what we’re talking about!

Gage Beasley's In-Demand Plush Toys
Gage Beasley’s In-Demand Plush Toys

Besides their neotenic uniqueness, axolotls have a significant role in understanding an organism’s regenerative properties, as they are experts at growing back body parts in no time and without leaving any scars!

Although very common as pets, wild axolotls are on the verge of extinction due to pollution, invasive species, and other threats. 

Therefore, learning more about axolotls and spreading the word is of the essence, as every small action contributes to conservation efforts.

Taxonomy and Classification

axolotls
Staring right back at ya! | Vitaliy Halenov via Getty Images

Axolotls are scientifically called Ambystoma mexicanum and are part of the Ambystoma genus, which is now widely renowned precisely because it hosts axolotls! 

Other members of the genus are the tiger salamander, the ringed salamander, the northwestern salamander, and other species.

Further up the taxonomic tree, Ambystoma is placed under the Ambystomatidae family of salamanders, which, in turn, is part of the Urodela order of lizard-like amphibians.

These paedomorphic or neotenic salamanders (you’ll soon learn what this means) are unique among amphibians precisely because of this characteristic.

Axolotls are often confused with mudpuppies and the larval form of tiger salamanders. While they’re closely related to the latter, the former are part of a completely different family.

Physical Characteristics

axolotls
Look how small this axolotl is! | MarioGuti via Getty Images

Adult axolotls are quite small, measuring only 15–45 centimeters (6–18 inches) long. 

However, they rarely reach their maximum size. Most individuals are 23 centimeters (9 inches) long and weigh only 300 grams (10.6 ounces).

They’re often mistaken for the larval form of the tiger salamander because they do indeed possess larval physical characteristics. 

The external gills, for example, are lost when typical salamanders reach adulthood, whereas axolotls keep them. 

Additionally, they also have a caudal fin extending from their heads toward the end of the tail.

Axolotls have an adorable appearance! They have wide heads and small, lidless eyes, just like other reptiles. 

Their teeth are vestigial, which means they are barely visible and not used for feeding.

There are three pairs of external gill stalks just behind their heads. They’re lined with filaments and serve as a hiding place for the gill ranks.

axolotls
The external gills of the axolotl | GlobalP via Getty Images

The four limbs of an axolotl are small and underdeveloped yet equipped with long digits. 

Males and females are sexually dimorphic; males have swollen papillae-lined cloacae (the opening for the reproductive, urinary, and digestive tracts), while females have much wider bodies.

Yet the most interesting aspect of an axolotl’s appearance is its skin color! 

Normally, axolotls are brown or tan and have an olive underside and gold speckles. 

However, many individuals retained mutant color combinations, of which the following are the most common:

  • The xanthic mutant color – gray skin and black eyes
  • The leucistic mutant color – pale pink skin and black eyes
  • The melanoid mutant color – fully black skin
  • The albino mutant color – pale pink or white skin and red eyes
  • The golden albino – golden skin and gold eyes.

Considering that pet breeders often mix the above mutant colors, some axolotls hatch with other unique combinations, like pink skin and pink eyes.

Habitat and Distribution


Axolotls thrive only in deep-water lakes with enough aquatic vegetation, which is extremely important for laying eggs. They’re highly sensitive to any changes in the quality of the water.

The native habitats of axolotl are Lake Xochimilco and Lake Chalc, located in the Valley of Mexico in central Mexico. However, both habitats have been destroyed. 

While Lake Xochimilco is still standing (although it’s highly destroyed as well), Lake Chalco has disappeared completely after being drained to control flooding.

Therefore, axolotls have disappeared from much of their natural range, although a few individuals are still living in Lake Xochimilco, Mexico City.

Besides the individuals living in the wild, many axolotls are now kept in aquariums as pets, as well as in laboratories in different parts of the world.

Behavior and Social Structure

axolotls
Axolotl underwater | izanbar via Getty Images

Unlike other salamanders, axolotls are fully aquatic due to their neotenic form. 

That’s why they also retain their external gills, whereas other salamanders lose them once they reach adulthood. 

Axolotls aren’t very friendly toward other amphibians, which isn’t very uncommon among reptiles, after all, as many species are known to be hostile even toward their peers. 

And even if they were friendlier, there aren’t too many individuals left in the wild for axolotls to form any kind of social structures and bonds.

Some sources mention that axolotls may become so aggressive toward each other that they even bite off the gills, tails, and feet of other axolotls!

However, this doesn’t cause much damage, as axolotls have a fascinating ability to regrow their body parts! And that’s not all! 

They even know exactly what needs to be regrown! If their arms are amputated at the wrist, they only grow the hand!

axolotls
White-pink Axolotl lurking in the dark | dmf87 via Getty Images

It remains unknown when axolotls are most active. Some specialists argue they are primarily nocturnal because they do not have keen eyesight. 

However, other theories indicate they have quite unpredictable routines and may also be active during the day.

Axolotls are poikilothermic creatures with fluctuating internal temperatures. 

Their metabolism highly depends on the environmental temperatures; the lower the temperature, the slower the metabolism. 

 This is why axolotls are highly sensitive to habitat changes.

Did you know that if they spend more than 24 hours at temperatures higher than 24 degrees Celsius (75 degrees Fahrenheit), axolotls can die?

Diet and Feeding

axolotls
Eating time, axolotl! | Argument via Getty Images

Axolotls are carnivorous amphibians.

They eat crustaceans, insects, worms, wounded fish, and tadpoles.

It has been suggested that axolotls rely on their sense of smell to find food.

Additionally, they have sensory organs aligned alongside their bodies, which help them sense prey.

Once they spot prey, axolotls pounce on it and suck it into their stomachs.

As mentioned, their teeth are almost invisible, so they’re of no use in killing and chewing prey.

Captive axolotls eat waxworms, earthworms, trout and salmon pellets, and feeder fish. 

Owners have noticed they may also ingest bedding material alongside their natural food sources.

Reproduction and Life Cycle

axolotls
Axolotl offspring, look at how many there are! | Samuel Santa Cruz via Getty Images

Axolotls are sexually mature once they’re approximately 12–18 months old.

During the breeding season (typically between March and June), the male engages in a unique courtship behavior during which it kind of dances, inviting the female to join it. 

Then, the male deposits a spermatophore, or a capsule containing spermatozoa, on the bottom of the lake, upon which the female shakes her tail over the spermatophore and picks it up with the cloaca.

Axolotls can lay as many as 300 eggs, which take approximately 14 days to hatch. 

The eggs are typically laid in aquatic vegetation, which is why habitat destruction affected the axolotl population so much. 

Another interesting thing to note is that each egg is laid separately and is surrounded by a distinctive protective jelly coat.

A few hours after hatching, the larvae can already eat by themselves. However, it takes roughly 14 days for them to become fully independent.

axolotls
Axolotl larva | Lumiphil via Getty Images

What’s of high interest in this section is the paedomorphic development of axolotls. 

This implies that they reach adulthood without metamorphosis, meaning their bodies do not undergo cell growth and differentiation. 

That’s why they have larval characteristics, like the presence of external gills, even though they’re sexually mature.

It has been proven that axolotls do not undergo metamorphosis because they lack the thyroid-stimulating hormone, which prevents their thyroid glands from producing thyroxine, a hormone required for metamorphosis.

However, even though they retain their larval form, axolotls still reach sexual maturity and can reproduce. 

Furthermore, scientists demonstrated that if axolotls were given thyroxine or an injection of iodine, they could undergo metamorphosis just like any other salamander.

If this happens, axolotls take the form of adult plateau tiger salamanders, except that their fingers would be longer than those of their relatives.

The lifespan of wild axolotls is unknown. The ones living in captivity, however, can reach 15 years, although the average life expectancy is 5–6 years.

Ecological Role and Interactions

Gage Beasley's Axolotl Soft Stuffed Plush Toy
Gage Beasley’s Axolotl Soft Stuffed Plush Toy

Axolotls were once top predators in their habitats and played a key role in maintaining well-structured communities.

Upon the introduction of non-native, invasive species, like the common carp and the Nile tilapia, axolotls are no longer at the top of the food chain, as these species stole their role as top predators.

Additionally, these fish target axolotl eggs and young, further threatening their population. 

As a consequence, axolotls started becoming less and less active to avoid predation.

Conservation Status and Threats

axolotls
The rare axolotl | AndreyTTL via Getty Images

The axolotl species was first assessed by the IUCN Red List in 1986, when it was classified as rare

Since then, their population steadily declined. As of 2006, the species is Critically Endangered.

Scientists estimate that their population suffered a decline of 80% over the past 16 years. 

Axolotls were even thought to have gone extinct several times, but specialists stumbled upon some individuals that confirmed otherwise.

It remains unknown how many axolotls are left in the wild, but estimations range between 50 and 1,000.

These are the main threats to the axolotl population:

  • Desiccation and pollution of the canal system lead to a low nitrogen-phosphorus ratio, low oxygen levels, and a high chlorophyll concentration.
  • Large agricultural areas where pesticides are used eventually kill axolotl embryos and larvae or cause them to develop abnormalities.
  • Increased tourist activity
  • Bacterial contamination
  • Pet trade
  • Traditional consumption (in the past)
  • Invasive species
  • Loss of genetic diversity caused by a small population number
axolotls
Lake Xochimilco, the home of the axolotl | Juan Manuel Gomez Ruano via Wikipedia (CC BY-SA 4.0)

Naturally, conservation efforts are in place to help these amphibians survive. 

Many specialists are trying to introduce captive-bred axolotls to new habitats or reintroduce them to their native ecosystem, Lake Xochimilco.

Nevertheless, these individuals are highly susceptible to developing various diseases after hundreds of years of inbreeding, and introducing them into a wild habitat is a risk.

The axolotl population number has not increased in the past few years, so future conservation efforts are required. 

They should be primarily focused on habitat management and restoration. 

Unique Adaptations and Survival Strategies

axolotls
If only we could regenerate limbs like the axolotl | Hailshadow via Getty Images

By far the most fascinating adaptation of axolotls is their regeneration ability. 

This is an excellent and fascinating survival strategy! Not only are they able to regenerate body parts, but they also do this much faster than other animals!

Axolotls can grow limbs, skin, bones, cartilage, and muscles. 

Studies have shown they can even regenerate a broken heart, as well as eye or brain parts! 

Some specialists suggest that axolotls are much more resistant to cancer than mammals! 

Considering that they can regenerate body parts so quickly, this isn’t in the least surprising!

Furthermore, axolotls are experts at hiding! Since the introduction of invasive species, axolotls are at risk of falling prey to other fish, so they have learned to stay hidden in vegetation and mud when larger fish are active.

Cultural Significance and Human Interactions

axolotls
Xolotl statue displayed at the Museo Nacional de Antropología in Mexico City. | Adamt via Wikipedia (CC0)

People have long been fascinated by axolotls, which were named in honor of Xolotl, a god of fire and lightning. 

This Aztec deity is portrayed as having the head of a dog and working as a soul-guide for the dead.

Xolotl is also an expert in transformations and is thought to have metamorphosed into an axolotl to prevent himself from dying, hence the naming of the salamander, which is now widely translated as the water-dog as it comes from the Aztec words for water (Atl) and dog (Xolotl). 

This can be a bit misleading, as the larval form of tiger salamanders is also called a waterdog.

Julio Cortazar, an Argentine novelist, wrote a story named Axolotl

Julio Cortazar’s Axolotl | Photo via Goodreads

The narrator is a regular visitor to a local zoo who’s fascinated by the adorable axolotls living there. 

He spends hours watching these awe-inspiring amphibians, and, in the end, he identifies so much with them that he proclaims himself an axolotl, too.

He says that the head of an axolotl reminds him of the human head, while its eyes are full of knowledge, suggesting that their consciousnesses are trapped inside a little, fragile body.

Axolotls also served as inspiration for the Pokemon Wooper in Pokemon Gold, Silver, and Crystal, as well as for some dragons in How to Train Your Dragon

Last but not least, the axolotl appears on a 50-peso banknote!

Future Prospects and Research

axolotls
The axolotl (Ambystoma mexicanum) paedomorphic salamander, critically endangered amphibian in the family Ambystomatidae, endemic to Mexican lakes of Xochimilco and Chalco | Artur Bogacki via Getty Images

Axolotls live in several captive colonies around the world, where they’re cared for by scientists concerned with studying their regenerative abilities. 

This research can lead to breakthrough discoveries in understanding the regenerative abilities of mammals.

Since axolotls are also known to be highly resistant to cancerous tissues, their significance in current and future research papers is undeniable, as they can help scientists unlock medicinal opportunities related to cancer.

Axolotls aren’t new to the scientific world. Specialists have been studying them for hundreds of years. 

Did you know they served as the basis for understanding human spina bifida (an undeveloped spine at birth)? 

Besides this, axolotls are the main reason specialists know how vertebrates develop.

In short, axolotls can one day become the key to helping hundreds of thousands of people thanks to their unique surviving adaptations!

Conclusion

Axolotls are adorable salamanders that retain their juvenile form throughout their whole lives! 

Not only are they fascinating creatures in the wild thanks to their unique adaptations, but they also hold a great deal of importance in medicinal studies.

These Mexican walking fish keep their external gills and caudal fins and lead a fully aquatic lifestyle. 

They’re native to Lake Xochimilco and Lake Chalco in Mexico.

Today, however, they’re found in small numbers only in Lake Xochimilco, which is also susceptible to dangerous pollutants and other threats that have brought the axolotl population to the brink of extinction.

Although axolotls are now found in several captive colonies and are kept as pets throughout the world, this may not contribute too much to balancing the wild population.

Needless to say, conservation efforts must be oriented toward habitat management.

Spreading the word about the importance of these creatures is of the essence in raising awareness and contributing to conservation efforts.

FAQs

Do axolotls only live underwater?

Axolotls are fully aquatic creatures. They won’t survive for too long if taken out of the water.

Can you keep an axolotl as a pet?

It’s illegal to keep axolotls as pets in some regions, so it is best to check the local exotic pet laws to ensure this is possible.

Do axolotls swim fast?

Some sources mention they can move at a speed of 15 km/h (9.3 mph), but this hasn’t been scientifically confirmed.

Sources:

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