Axolotl

Quick Take

• Axolotls can regenerate their spines, organs, and even parts of their brains, yet there is a chemical trick that forces them to give all of that up permanently. Permanent larval state →
• They've been called 'Mexican walking fish' for decades, but almost everything that name implies is wrong. Name origins explained →
• Axolotls exist in the millions as pets, yet wild individuals can now be counted in the hundreds, and their conservation status is far more complicated than 'endangered' suggests. Wild population crisis →
• Scientists think axolotls never fully grow up, and the reason why may trace back to a 10,000-year evolutionary clock that ran out of time. Axolotl evolutionary history →

Axolotls are often referred to as “Mexican walking fish,” but they are actually amphibians that prefer to live their entire lives underwater. These remarkable creatures can regenerate almost every part of their bodies if necessary, including their spines, internal organs, and even some parts of their brains. They have a unique appearance and are extremely popular as exotic pets, but they can also be found in captivity at zoos, laboratories, and breeding facilities. There are almost none of these creatures left in the wild.

Incredible Axolotl Facts

• Axolotls can regenerate their limbs as well as their spines, brains, and nearly every other body part.
• They exhibit a trait called neoteny, which means that they never outgrow their juvenile characteristics like other salamanders. For example, they have both gills and lungs.
• The name “axolotl” is most authoritatively translated as “servant of water,” though it is also commonly rendered as “water dog.”
• They are commonly called “Mexican walking fish” even though they are not fish at all.

Evolution

From an evolutionary perspective, axolotls are comparatively young in contrast to other Mexican salamanders. Scientists estimate that they have only been in their native habitat for about 10,000 years. These creatures did not have long to flourish, for around the thirteenth century their home began to be settled by humans. After the land was claimed by Spain in the 1500s, urbanization began to accelerate until the area became modern-day Mexico City, leaving only a tiny fraction of the axolotl’s habitat for them to live in. Biologists have taken note of how axolotls express traits in adulthood that other amphibians only show during adolescence, like breathing underwater, and hypothesize that this could be because of their incredibly brief chance to evolve before their populations became seriously threatened.

Classification and Scientific Name

The axolotl’s scientific name is Ambystoma mexicanum. There is some debate regarding the origin of the name, however. The genus was named by Johann Jakob von Tschudi in 1839, and he did not provide information regarding the derivation of the name.

Some believe that he meant for the name to be Amblystoma, which means “blunt mouth” and is derived from the Latin ambly, or “dull,” and stoma, or “mouth.” Because it’s unclear whether or not Tschudi made an error, the genus name remains unchanged.

Appearance

Axolotls can have a variety of color variations. Normal axolotls are an olive-tan color with gold speckles, but there are genetic mutations that can cause different coloring. Leucistic axolotls display pale white or pink skin with black eyes. Albinos have vibrant gold skin and matching eyes. Axanthic types are gray with black eyes. Melanoids are solid black with no other coloring. In addition to these natural mutations, exotic pet breeders will also intentionally cross-breed certain variants to produce new and interesting color combinations for novelty purposes.

Male and female axolotls can grow to be up to 12–18 inches long, but the average size is typically around 9–12 inches. They can also weigh up to 8 ounces. They have wide, somewhat flat heads with lidless eyes and thin mouths that appear to be smiling. They have three branched gills that protrude from either side of the head, and they retain their larval dorsal fin throughout their lives. In addition, their limbs are small and underdeveloped, and they feature long, slender digits that resemble fingers.

Once they reach sexual maturity, males and females are easy to tell apart. Males develop a large, swollen cloaca, and their tails typically grow longer. Females develop much wider bodies because they can carry anywhere from 300 to 1,000 eggs at a time.

Behavior

In general, axolotls are solitary creatures. They prefer not to interact with humans, and they live by themselves in the wild unless they are mating, often hiding among plants and rocks at the bottom of the lakes in which they live.

Habitat

Axolotls are native to the Valley of Mexico and can only be found in the Lake Xochimilco region. In the past, they could also be found in Lake Chalco, but every acre of land in that area has been drained in order to prevent flooding, so these creatures had to migrate.

Despite the fact that they are part of the salamander family, they live entirely in the water. The waters of Lake Xochimilco are usually about 65 degrees Fahrenheit, which falls well within the 60 to 70 degree comfort zone that these creatures prefer to live in. They can be found at the bottom of the lake, surrounded by plants and rock structures in which to hide.

Population

Currently, the IUCN has listed the axolotl as a critically endangered species, and this means that they are on the brink of becoming extinct in the wild. Mexico City’s urban sprawl has caused a severe decline in the axolotl population, and as the demands of Mexico City have steadily increased, more of this creature’s native surroundings in the Lake Xochimilco area have been drained or contaminated; this habitat loss is a major contributing factor to their population decline.

Researchers are not sure exactly how many axolotls exist in the wild currently, but the most optimistic estimate is in the hundreds. The most recent count showed only 36 axolotls per square kilometer in their natural habitat, so their numbers are incredibly low. They are bred extensively in captivity as pets and food; however, their conservation status remains complex, as captive populations do not offset the decline of wild ones.

Diet

The axolotl is carnivorous, and in the wild, it will typically eat worms, crustaceans, small fish, mollusks, insects, and insect larvae. The ones that live in captivity are usually fed a diet that consists of salmon pellets, black worms, bloodworms, white worms, and Daphnia. Anyone keeping one of these creatures as a pet should be sure to feed it a protein-rich diet in order to keep it healthy.

Predators

Axolotls face a number of threats from both human and animal predators. Roasted axolotls are considered a delicacy by many, and there are also huge numbers of people who capture them to sell for profit.

The introduction of non-native species such as the Asian carp and African tilapia has also hurt the wild axolotl population because these fish will eat their young as well as the small prey that they survive on.

Reproduction, Babies, and Lifespan

In the wild, axolotls typically live up to 15 years. In captivity, their lifespan is usually longer, and they commonly live 15 to 20 years, with some individuals living past 20 years. These creatures generally reach sexual maturity anywhere from 7 to 18 months. Some may take up to 27 months to reach full maturity, but they are always still in their larval form when maturation happens.

Axolotls breed in late winter or early spring, and their mating rituals involve a courtship dance that relies on visual and chemical signals, allowing the female to locate and insert the sperm capsules deposited by the male.

Females can lay anywhere from 100 to 1,000 eggs in a single spawning. Each egg is laid individually, and females prefer to lay their eggs on plants when possible. The eggs will hatch after incubating for 14 days at 75 degrees Fahrenheit, and the larvae will begin eating within their first few hours of life. Baby axolotls will remain larvae even as they reach sexual maturity; that’s because axolotls never leave their larval stage. In fact, if you inject an axolotl with iodine, it will force a metamorphosis causing them to lose their gills and transform into a terrestrial salamander.

Axolotl parents do not care for their larvae. In fact, they are not averse to eating their own eggs or their own babies. This is something that breeders and pet owners must carefully account for.

Keeping an Axolotl as a Pet

Axolotls have become popular in the exotic pet trade. They can make great pets, but be aware that they can be challenging for beginner pet owners who have not previously cared for amphibians. Axolotls require large water tanks and relatively uniform water temperatures that accommodate their sensitive skin. Purchasing an axolotl generally costs about $20 to $70, but the real expense will come from tank set-ups, keeping an axolotl fed, and potential vet check-ups. Keep in mind that axolotls can live over 10 years in captivity, so purchasing one as a pet can be a long-term commitment.

Axolotl in Zoos

There are many zoos across the United States that feature axolotl exhibits so that you can see these fascinating creatures up close and learn more about them. A few of the most well-known exhibits can be seen at the San Diego Zoo, the Lincoln Park Zoo, and the Detroit Zoo.

Types of Axolotl

While axolotls are just one species of mole salamander, they can display a wide spectrum of genetic variation visible in a variety of gorgeous colors. Breeders have sought to accentuate these traits by manipulating the chromatophores, or pigment cells, so that each can be sold as a recognizable specimen of its type. New and unique types of axolotl are being discovered and bred all the time. Below you can find a list of all of the most popular varieties of axolotl.

• Wild Axolotl
• Leucistic Axolotl
• White Albino Axolotl
• Golden Albino Axolotl
• Melanoid Axolotl
• Axanthic Axolotl Morph
• Copper Axolotl Morph
• GFP (Green Fluorescent Protein) Axolotl Morph
• Chimera Axolotl Morph
• Mosaic Axolotl Morph
• Silver Dalmatian Axolotl Morph
• Enigma Axolotl Morph
• Firefly Axolotl Morph