close
Jump to content

Axolotl

Checked
Page protected with pending changes
From Wikipedia, the free encyclopedia

Axolotl
Image
The wild type form
CITES Appendix II[2]
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Amphibia
Order: Urodela
Family: Ambystomatidae
Genus: Ambystoma
Species:
A. mexicanum
Binomial name
Ambystoma mexicanum
(Shaw and Nodder, 1798)
Map
IUCN range of the axolotl
  Axolotl (Ambystoma mexicanum)
Synonyms[3]
  • Gyrinus mexicanus Shaw and Nodder, 1798
  • Siren pisciformis Shaw, 1802
  • Siredon axolotl Wagler, 1830
  • Axolotes guttata Owen, 1844
  • Siredon Humboldtii Duméril, Bibron, and Duméril, 1854
  • Amblystoma weismanni Wiedersheim, 1879
  • Siredon edule Dugès, 1888

The axolotl (/ˈæksəlɒtəl/ ; from Classical Nahuatl: āxōlōtl [aːˈʃoːloːtɬ] ; Ambystoma mexicanum) is a species of mole salamander. It is neotenic, reaching sexual maturity without undergoing metamorphosis, and the adults remain fully aquatic with obvious external gills. Axolotls may be difficult to distinguish from the larval stage of other neotenic adult mole salamanders, in particular the tiger salamander, or other species such as mudpuppies.[4]

Axolotls originally inhabited a system of interconnected wetlands and lakes in the highlands of Mexico. They were known to inhabit the smaller lakes of Xochimilco and Chalco and are presumed to have inhabited the larger lakes of Texcoco and Zumpango. The desiccation of these lakes, initiated by the Aztecs and accelerated during the 20th century,[5][6][7] has led to the destruction of much of the axolotl's natural habitat, an area now largely occupied by Mexico City. Wild axolotls have been driven to near extinction by the introduction of invasive species such as tilapia and carp; with a decreasing population of around 50 to 1,000 adult individuals, the species has been assessed as critically endangered by the International Union for Conservation of Nature (IUCN) and is listed under Appendix II of the Convention on International Trade in Endangered Species (CITES).[2]

There currently exists a large captive population of axolotls, with specimens used extensively in scientific research because of their unusual ability to regenerate body parts, including limbs, gills and parts of their eyes and brains. The species is also used as a model organism. As aquarium technology has developed, axolotls have become a common exhibit in zoos and public aquariums, as well as an occasional pet in home aquariums. The axolotl is a popular subject in contemporary culture, inspiring a number of works and characters in the media.

Nomenclature

[edit]

The term "axolotl" is a Nahuatl word which has been translated variably as "water slave", "water servant", "water sprite", "water player", "water monstrosity", "water twin", or "water dog".[8][9][10] The word refers to Xolotl, the Aztec god who holds dominion over fire, lightning, the dead and the resurrected, dogs, games, grotesque or ugly beings, and twins (as he is the twin of Quetzalcōātl).[8][11]

Some sources prefer the term "Mexican axolotl" to refer to this species unambiguously, as "axolotl" may be used for unmetamorphosed individuals of other Ambystoma species,[10][12] although the word is most commonly used to refer to wild A. mexicanum and captive individuals.

Description

[edit]
Image
Image
Head of a dark-colored, perhaps wild type, axolotl

A sexually mature adult axolotl, at age 18–27 months, ranges in length from 15 to 45 cm (6 to 18 in); a size close to 23 cm (9 in) is most common, and any greater than 30 cm (12 in) is rare. Axolotls possess features typical of salamander larvae, including external gills and a caudal fin extending from behind the head to the vent.[13][14] Unlike most salamander species, axolotls retain their external gills when they mature into adulthood.[15] This is a type of neoteny.[16]

Axolotls have wide heads and lidless eyes. Their limbs are underdeveloped and possess long, thin digits. Three pairs of external gill stalks (rami) originate from behind the head and are used to move oxygenated water. These are lined with filaments (fimbriae) to increase the surface area for gas exchange.[15] Four gill slits lined with gill rakers are hidden underneath the external gills, which prevent food from entering and allow particles to filter through. Males can be identified by their swollen cloacae lined with papillae, while females have noticeably wider bodies when gravid and full of eggs.

Image
Buccal pumping

Axolotls have barely visible vestigial teeth; other salamanders only develop these during metamorphosis. Their primary method of feeding is by suction, during which their rakers interlock to close the gill slits. Axolotls use their external gills for respiration; buccal pumping (gulping air from the surface) may also be used to provide oxygen to their lungs.[15] Buccal pumping can occur in a two-stroke manner, pumping air from the mouth to the lungs, or a four-stroke manner, reversing this pathway using compression forces.

Image
Image
Captive axolotl color morphs

The wild type animal (the "natural" form) is brown or tan with gold speckles and an olive undertone. They can subtly alter their color by changing the relative size and thickness of the melanophores, presumably for camouflage.[17] Axolotls have four pigmentation genes; when mutated, they create different color variants.[18] The four most common mutant colors are as follows:

  1. Leucistic: pale pink body, black eyes
  2. Xanthic: grey body, black eyes
  3. Albinism: pale pink or white body, red eyes
  4. Melanism: black or dark blue body with no gold speckling or olive tone

In addition, there is wide individual variability in the size, frequency, and intensity of the gold speckling, and at least one variant leads to the development of a black and white piebald appearance upon reaching maturity.[19] Pet breeders frequently cross the variant colors, and double homozygous mutants are common in the pet trade, especially white/pink animals with pink eyes that are double homozygous mutants for both the albino and leucistic genes.[20]

Image
Melanophores of a larva axolotl

The 32 billion base pair long sequence of the axolotl's genome was published in 2018; the largest animal genome completed at the time, it revealed species-specific genetic pathways that may be responsible for limb regeneration.[21] Although the axolotl genome is about ten times the size of the human genome, it encodes a similar number of proteins (23,251,[21] compared with about 20,000 in the human genome). The size difference is mostly explained by a large fraction of repetitive sequences; these also contribute to increased median intron sizes (22,759 bp), which are 13, 16 and 25 times that observed in human (1,750 bp), mouse (1,469 bp) and Tibetan frog (906 bp), respectively.[21]

Physiology

[edit]

Regeneration

[edit]

The feature of the axolotl that attracts most attention is its healing ability: the axolotl does not heal by scarring, but is capable of tissue regeneration. Entire lost appendages such as limbs and the tail can regrow over a period of months, and in certain cases, more vital structures, such as the tissues of the eye and heart, can be regrown.[22][23] They can even restore parts of their central nervous system, such as less vital parts of their brains. Moreover, they can readily accept transplants from other individuals—including eyes and parts of the brain—restoring these "alien organs" to full functionality. In special cases, axolotls have been known to repair a damaged limb while also regenerating an additional one, ending up with an extra appendage which makes them attractive to pet owners as a novelty.[24]

There are three basic requirements for regeneration of a limb: (1) the wound epithelium, (2) nerve signaling, and (3) the presence of cells from the different limb axes.[25][clarification needed] A wound epidermis is quickly formed by the cells to cover up the site of the wound. In the following days, the cells of the wound epidermis divide and grow, quickly forming a blastema, which means the wound is ready to heal and undergo patterning to form the new limb. It is believed that during limb generation, axolotls have a different system to regulate their internal macrophage level and suppress inflammation, as scarring prevents proper healing and regeneration.[26] However, this belief has been questioned by other studies.[27]

The apical-ectodermal ridge (AER), a fundamental growth structure with the apical-ectodermal cap (AEC), is one of the few things given credit for the axolotl's ability to regenerate whole limbs in early development.[28][clarification needed] The apical ectodermal ridge is a structure in embryos that starts the growth of appendages by signaling how they are shaped and extended.[28] These cells[clarification needed] are needed to form limbs in most tetrapods, amphibians, and humans. Unlike most other animals, the AEC in the axolotl can send signals through growth hormones to activate blastema cells, which can rebuild whole amputated or damaged limbs or organs.[29][verification needed]

Axolotls also experience indeterminate growth, meaning their bodies continue to grow throughout their life; some consider this trait to be a direct contributor to their regenerative abilities. Their ability to regenerate declines with age but does not disappear, though in metamorphosed individuals, the ability to regenerate is greatly diminished.[24]

Neoteny

[edit]

Most amphibians begin their lives as aquatic animals unable to live on dry land, often called tadpoles. To reach adulthood, they go through a process called metamorphosis, in which they lose their gills and start living on land. The axolotl is unusual in that it has a lack of the thyroid-stimulating hormone that triggers the thyroid to produce thyroxine, which is needed for metamorphosis to take place; instead, the axolotl keeps its gills and lives in water all its life, even after becoming an adult and able to reproduce. The trait of reaching sexual maturity without undergoing metamorphosis is called neoteny.[35]

The genes responsible for neoteny in laboratory axolotls may have been identified; they are not linked to the genes of wild populations, suggesting artificial selection is the cause of complete neoteny in laboratory and pet axolotls.[36] The genes responsible have been narrowed down to a small chromosomal region called met1, which contains several candidate genes.[37]

Many other species within the axolotl's genus are also either entirely neotenic or have neotenic populations. Sirens, Necturus mudpuppies, and the troglobitic olm are other examples of neotenic salamanders, although unlike axolotls they cannot be induced to metamorphose by an injection of iodine or thyroxine hormone.[citation needed]

Metamorphosis

[edit]
Image
Metamorphosed axolotls

Over evolutionary time, the axolotl has lost the ability to naturally undergo metamorphosis.[38] It has retained the capacity to undergo metamorphosis if provided with the necessary hormones through artificial administration.[39] Under modern laboratory conditions, metamorphosis is reliably induced by administering thyroid hormones, including thyroxine, triiodo-L-thyronine, or thyroid-stimulating hormones.[40][38]

Depending on the hormone used for induction, different outcomes may occur. Some hormones, such as triiodo-L-thyronine, can promote regenerative abilities while in some cases failing to produce complete metamorphosis.[38] In contrast, thyroxine can inhibit regenerative abilities and accelerate metamorphosis.[38]

After an axolotl undergoes hormonally induced metamorphosis and begins living on land, it experiences a number of physiological changes that help it adapt to terrestrial life. These include increased muscle tone in limbs, resorption of gills and fins into the body, the development of eyelids, and a reduction in the skin's permeability to water, allowing the axolotl to remain more effectively hydrated on land. The lungs of an axolotl, though present alongside gills after reaching non-metamorphosed adulthood, develop further during metamorphosis.[41] Axolotls that complete metamorphosis are similar in appearance to the adult plateau tiger salamander, though axolotls have longer toes.

In the absence of induced metamorphosis, larval axolotls begin absorbing iodide into their thyroid glands at around 30 days post-fertilization. Larval axolotls do produce thyroid hormones from iodide, but the amount appears highly variable. In contrast, adult axolotls do not produce detectable levels of thyroid hormone unless metamorphosis is triggered.[42]

Wild population

[edit]
Image
Image
Lake Xochimilco, one of the last refuges of the wild axolotl

Axolotls are within the same genus as the tiger salamander (Ambystoma tigrinum), being part of its species complex along with all other Mexican species of Ambystoma.[43][44][45] Within Ambystomatidae, the closest relative of the axolotl is the Eastern tiger salamander.[46] Their habitat is like that of most[verify] neotenic Ambystoma species: a high-altitude body of water surrounded by a risky terrestrial environment or other conditions unsuitable for the terrestrial form, with these conditions thought to favor the development of neoteny.[47] However, a population of terrestrial Mexican tiger salamanders occupies and breeds in the axolotl's habitat (being sympatric).[citation needed] The axolotl is native to the freshwater Lakes Xochimilco and Chalco in the Valley of Mexico (though the species may have also inhabited the larger Lakes of Texcoco and Zumpango).[1] Lake Chalco is an unstable ecosystem, often being drained as a flood control measure, and Lake Xochimilco is a remnant of its former self, existing mainly as canals. The water temperature in Xochimilco rarely rises above 20 °C (68 °F), and may fall to 6–7 °C (43–45 °F) or lower in the winter.[48][verification needed] An additional population of Ambystoma inhabiting the artificial lake at Chapultepec was confirmed to contain axolotls; the extent of occurrence as of 23 October 2019 was 467 square kilometres (180 sq mi).[1] Overall, the wild axolotl prefers a system of water channels and deep-water lakes with abundant aquatic vegetation.[1]

Biology

[edit]
Image
Wild form

The axolotl is carnivorous; in the wild, it consumes small prey such as mollusks,[49] worms, aquatic insects, other arthropods (such as crayfish),[49][50] and small fish, as well as other salamanders (including conspecifics).[49][51] Axolotls locate food by smell and will "snap" at any potential meal, sucking the food into their stomachs with vacuum force.[52] The wild axolotl is thought to reach sexual maturity at 1.5 years of age, with a generation length of around 5.5 years.[1] The life expectancy of a wild axolotl is between 10 and 15 years.[47]

Threats

[edit]

Axolotls are native only to the Mexican Central Valley, and the population once extended through most of the lakes and wetlands in this region. The axolotl's natural habitat is now limited to Lake Xochimilco as a result of the expansion of Mexico City and is under pressure from the city's growth. The axolotl is on the IUCN Red List of threatened species.[1]

Surveys conducted in 1998, 2003, and 2008 found populations of 6,000, 1,000, and 100 axolotls per square kilometer, respectively, in Lake Xochimilco.[53] A four-month-long search in 2013 found no surviving individuals in the wild, but one month later two were spotted in a network of canals leading from Xochimilco.[54]

Lake Xochimilco has poor water quality; tests have revealed a low nitrogen-to-phosphorus ratio and a high concentration of chlorophyll a, indicative of an oxygen-poor environment not well-suited to axolotls. This has been caused by the demands of local industries, such as aquaculture and agriculture, which maintain the lake's water levels through inputs of partially treated wastewater.[55] Intensively used agricultural pesticides eventually enter the lake through runoff, and these contain chemical compounds that sharply increase the mortality rate in axolotl embryos and larvae. Of the surviving embryos and larvae, there is also an increase in morphological, behavioral, and activity abnormalities.[56][when?]

With such a dramatic reduction in the native population, there has been a significant loss of genetic diversity. This can be dangerous for the remaining population, as it causes increased inbreeding and reduced fitness and adaptive potential. Studies have found indicators of low interpopulation gene flow and higher rates of genetic drift. These are likely the result of multiple "bottleneck" incidents, where a sharp drop in the number of individuals in the population leads to decreased genetic diversity. The offspring produced after bottleneck events have a greater risk of poor fitness and are often less able to adapt. Several bottleneck events may even lead to extinction. Studies have also found high rates of relatedness indicative of inbreeding, which can cause an increase in the presence of deleterious, or harmful, mutations in genes.[57] The detection of introgressed tiger salamander (A. tigrinum) DNA in the laboratory axolotl population raises concerns about the suitability of the captive population as an "ark" for potential reintroduction purposes.[58]

Another factor that threatens the population is the introduction of invasive fish species, such as the Nile tilapia and the common carp. These fish eat the axolotls' young and compete for their food.[59] The presence of these species has changed axolotl behavior, causing them to be less active in an effort to avoid predation. This reduced activity greatly impacts the axolotl's foraging and mating opportunities.[60]

The fungus Batrachochytrium dendrobatidis has been detected in axolotls; this fungus causes the disease chytridiomycosis in amphibians and is a major concern for amphibian conservation worldwide. However, the axolotl displays resistance to both B. dendrobatidis and B. salamandrivorans, so chytridiomycosis is thought not to be a threat to this species.[1]

Conservation efforts

[edit]

The condition of the native axolotl population has improved little over the years.[61][62] Many scientists are focusing their conservation efforts on the translocation of captive-bred individuals into new habitats or their reintroduction into Lake Xochimilco. Studies have shown that axolotls born in captivity and raised in a semi-natural environment are capable of surviving in the wild, catching prey and escaping predators with moderate success. These captive-bred individuals may be introduced into unpolluted bodies of water or returned to Lake Xochimilco; however, with the amount of pollution in the lake, the presence of invasive species and the region's continuing urbanization, the translocated axolotls might eventually have the same fate as the wild population.[63][64]

The Laboratorio de Restauracion Ecologica (transl. Laboratory of Ecological Restoration) of the National Autonomous University of Mexico has built up a population of 100 captive-bred axolotls, as of 2021. These are mostly used for research, but there are plans to establish a viable population in a semi-artificial wetland inside the university.[needs update][citation needed]

A 2025 study confirmed the viability of releasing captive-bred axolotls into the wild, with recaptured individuals having gained weight since their release. However, this practice risks losing the axolotls through predation, as several of those released were preyed on by great egrets.[65][66][67]

Relation to humans

[edit]

Research history

[edit]

German naturalist and explorer Alexander von Humboldt noted in the 19th century that the Mexicans, having been vanquished by the Spanish Empire, lived "in great want, compelled to feed on roots of aquatic plants, insects and a problematical reptile called axolotl".[68]

In 1863, a shipment of 34 adult axolotls was sent from Mexico City to the Jardin des Plantes in Paris, from which thousands of specimens were captive-bred and distributed around Europe for scientific research.[69] Unaware of their neoteny, French zoologist Auguste Duméril was surprised when, instead of the axolotl, he found in the vivarium a new species, similar to the salamander. This discovery was the starting point of research about neoteny. It is not certain that Ambystoma velasci specimens were not included in the original shipment.[clarification needed][citation needed]

In Prague, the Czech physician Vilem Laufberger used thyroid hormone injections to induce an axolotl to grow into a terrestrial adult salamander. Unaware that it had already been carried out, Englishman Julian Huxley repeated the experiment using ground animal thyroid glands.[70][71] Since then, experiments have often involved the injection of iodine or various thyroid hormones to induce metamorphosis.[16]

Use as a model organism

[edit]
Image
Stages of development (images captured using stereoscopic macrophotography)

Bred in captivity in large numbers, the axolotl is used extensively in research as a model organism. They are especially easy to breed compared with other salamanders in the Ambystomatidae family, which are rarely captive-bred because of the husbandry demands of terrestrial life. One attractive feature of the axolotl for research purposes is the large and easily manipulated embryo, which allows viewing of the full development of a vertebrate. Axolotls are used in heart defect studies due to the presence of a mutant gene that causes heart failure in embryos. Since the axolotl embryo survives almost to hatching with no heart function, the defect is very observable. Further research has been conducted to examine the axolotl's heart as a model of a single human ventricle and excessive trabeculation.[72] The axolotl is also considered an ideal animal model for the study of neural tube closure due to the similarities between human and axolotl neural plate and tube formation; the axolotl's neural tube, unlike that of a frog, is not hidden under a layer of superficial epithelium.[73] There are additional mutations affecting other organ systems, some of which are not yet well characterized.[74]

The regenerative abilities of the axolotl have led to its use as a model for the development of limbs in vertebrates, with the goal of understanding how humans can achieve better ways to heal from serious injuries.[75] This also makes the species the perfect model organism for studying the properties of stem cells and the process of neoteny. Current research can record specific examples of the axolotl's regenerative properties through tracking cell fates and behaviors, lineage tracing from skin triploid cell grafts, pigmentation imaging, electroporation, tissue clearing and lineage tracing from dye labeling. The newer technologies of germline modification and transgenesis are better suited for live imaging the regenerative processes that occur for axolotls.[76]

In a 2025 study, scientists found a new method of inserting and activating the genes inside the axolotl's brain and nervous system using special, harmless viruses called adeno-associated viruses (AAVs). It had previously been difficult for researchers to make specific genes work inside the axolotl, but this discovery allows them to explore how the axolotl's nervous system helps it regrow body parts such as the brain and spinal cord. Additionally, they found that the axolotl's nervous system has a unique two-way communication between the brain and eye.[77]

The genetics of the color variants of the axolotl have also been widely studied.[20]

Captive care

[edit]
Image
This animal was X-rayed several times as part of a research project over a period of two years. It was a normal healthy adult (26.3 cm; 159.5 gm) at the beginning of the project and lived several more years after the project ended.[28]

The axolotl is a popular exotic pet like its relative, the tiger salamander (Ambystoma tigrinum). As for all poikilothermic organisms, lower temperatures result in slower metabolism and reduced appetite. Temperatures at approximately 16 °C (61 °F) to 18 °C (64 °F) are suggested for captive axolotls to ensure sufficient food intake; temperatures higher than 24 °C (75 °F) may lead to metabolic rate increase, also causing stress and eventually death.[78][79] Chlorine, commonly added to tap water, is harmful to axolotls.[80][81] A single axolotl typically requires a 150-litre (40-US-gallon) tank. Axolotls spend the majority of the time at the bottom of their tanks.[82]

In captivity, axolotls eat a variety of readily available foods, including trout and salmon pellets, frozen or live bloodworms, earthworms, and waxworms. Axolotls can also eat feeder fish, but care should be taken as fish may contain parasites.[83]

Substrates are another important consideration for captive axolotls, as axolotls (like other amphibians and reptiles) tend to ingest bedding material together with food[84] and are commonly prone to gastrointestinal obstruction and foreign body ingestion.[85] Some common substrates used for animal enclosures can be harmful for amphibians and reptiles. Gravel (common in aquarium use) should not be used, and is recommended that any sand consists of smooth particles with a grain size of under 1mm.[84] One guide to axolotl care for laboratories notes that bowel obstructions are a common cause of death, and recommends that no items with a diameter below 3 cm (or approximately the size of the animal's head) should be available to the animal.[86]

There is some evidence that axolotls might seek out appropriately-sized gravel for use as gastroliths[87] based on experiments conducted at the University of Manitoba axolotl colony.[88][89] As there is no conclusive evidence pointing to gastrolith use, gravel should be avoided due to the high risk of impaction.[90]

Salts, such as Holtfreter's solution, are often added to the water to prevent infection.[91] Among hobbyists, the process of artificially inducing metamorphosis can often result in death during or even following a successful attempt, and so casual hobbyists are generally discouraged from attempting to induce metamorphosis in pet axolotls.[41] Morphed pet axolotls should be given solid footholds in their enclosure to satisfy their need for land. They should not be given live animals as food.[92]

Cultural significance

[edit]
Image
Axolotl graffiti in Mexico City

The species is named after Xolotl, the Aztec god of fire and lightning, who transformed himself into an axolotl to avoid being sacrificed by fellow gods. Axolotls continue to play a substantial cultural role in Mexico.[93] For example, they appear in the works of Mexican muralist Diego Rivera.[citation needed] In 2021, Mexico released a new design for the 50-peso banknote featuring an axolotl on its reverse.[94][95] It was recognized as "Bank Note of the Year" by the International Bank Note Society.[96] With a face value of less than three US dollars, the new banknote has become a collectable item because of its very popular design; the Bank of Mexico reported in 2025 that up to 50 million were being kept out of circulation, as millions of people were choosing to hoard the notes rather than spend them.[97]

In Japan, the creatures are commonly known as "wooper loopers" (ウーパールーパー) following a 1980s marketing campaign by Nissin Foods featuring an axolotl with that name.[98][99] In 1999, the video games Pokémon Gold and Silver, made by Japanese developer Game Freak, introduced a Pokémon named Wooper, which is directly based on an axolotl.[93][100] Additionally, in 2002, Pokémon Ruby and Sapphire introduced the Pokémon Mudkip and its evolutions, which take some visual inspiration from axolotls.[93][additional citation(s) needed]

Image
Axolotl as seen in an official Minecraft animation

Starting in the late 20th and early 21st century, the axolotl became renowned as a cultural icon, with its likeness appearing in, or inspiring, various aspects of contemporary media, such as television shows, movies, or video games. Axolotls were added to the video game Minecraft in 2020 (depicted as troglofauna in-game), following Mojang Studios' trend of incorporating endangered species to raise awareness,[101] and they were included in its spin-offs Minecraft: Dungeons and Lego Minecraft.[102][103] In the How to Train Your Dragon movie franchise, the dragon Toothless was also modeled after axolotls.[93]

Julio Cortázar wrote a short story titled "Axolotl", in which the narrator encounters axolotls in the aquarium at the Jardin des Plantes de Paris.[104][105]

In 2019, a star in the equatorial constellation of Cetus was named Axólotl.[106][107]

See also

[edit]

References

[edit]
  1. ^ a b c d e f g IUCN SSC Amphibian Specialist Group (2020). "Ambystoma mexicanum". IUCN Red List of Threatened Species. 2020 e.T1095A53947343. doi:10.2305/IUCN.UK.2020-3.RLTS.T1095A53947343.en. Retrieved 12 November 2021.
  2. ^ a b "Appendices | CITES". cites.org. Retrieved 14 January 2022.
  3. ^ Frost, Darrel R. (2018). "Ambystoma mexicanum (Shaw and Nodder, 1798)". Amphibian Species of the World: an Online Reference. Version 6.0. American Museum of Natural History. Retrieved 10 August 2018.
  4. ^ Malacinski, George M. (Spring 1978). "The Mexican Axolotl, Ambystoma mexicanum: Its Biology and Developmental Genetics, and Its Autonomous Cell-Lethal Genes". American Zoologist. 18 (2): 195–206. doi:10.1093/icb/18.2.195.
  5. ^ Alcocer, J.; Williams, W. D. (1 March 1996). "Historical and recent changes in Lake Texcoco, a saline lake in Mexico". International Journal of Salt Lake Research. 5 (1): 45–61. doi:10.1007/BF01996035. ISSN 1573-8590. The Aztecs started the desiccation of Lake Texcoco by constructing low banks, levees or large hydraulic structures such as the Albarradón de Nezahualcóyotl. [...] In 1521, its area was almost 700 km2, by 1608, it was only 410 km2, by 1856, 350 km2, by 1904, 267 km2, and by 1966, only 140km2.
  6. ^ Lewis, Alan Christopher; Torres, Janet (September 2013). "The Ghosts of Lake Texcoco Still Haunting Mexico City". The Drop. 5. Water management & hydrological science program. Texas A&M University. The lakes never stood a chance, and by the mid-20th Century, the last vestiges of Lake Texcoco were completely drained.
  7. ^ "Regeneración del Rio La Piedad_Resumen Ejecutivo" [Regeneration of the La Piedad River_Executive Summary]. Issuu (in Spanish). 28 June 2011. Retrieved 11 April 2026.
  8. ^ a b Majchrzak, Amy. "Ambystoma mexicanum Salamandra ajolote". animaldiversity.org. University of Michigan. Retrieved 4 June 2025.
  9. ^ "Meet the Peter Pan of salamanders, the axolotl". worldwildlife.org. World Wildlife Fund. Retrieved 4 June 2025.
  10. ^ a b Humphrey, Rufus R. (1975). Robert C. King (ed.). Handbook of Genetics Volume 4: Vertebrates of Genetic Interest (4 ed.). New York: Springer. pp. 3–17. doi:10.1007/978-1-4613-4470-4. ISBN 978-1-4613-4470-4. Retrieved 4 June 2025.
  11. ^ "Why Aztecs Revered the Axolotl". history.com. 17 February 2026. Archived from the original on 16 March 2026. Retrieved 28 April 2026.
  12. ^ "Axolotl". Merriam-Webster.com Dictionary. Merriam-Webster. OCLC 1032680871. Retrieved 4 June 2025.
  13. ^ San Francisco Examiner (San Francisco, California) 7 August 1887, page 9, authored by Yda Addis
  14. ^ McIndoe, Rosemary; Smith, D.G. (1984). "4. Functional morphology of gills in larval amphibians". In Seymour, Roger S. (ed.). Respiration and metabolism of embryonic vertebrates: Satellite Symposium of the 29th International Congress of Physiological Sciences, Sydney, Australia, 1983. Perspectives in vertebrate science. Dordrecht: Springer Netherlands. pp. 55–69. doi:10.1007/978-94-009-6536-2_4. ISBN 978-94-009-6536-2.
  15. ^ a b c Kardong, Kenneth V (2019). Vertebrates: comparative anatomy, function, evolution. McGraw-Hill Education. ISBN 978-1-259-70091-0. OCLC 1053847969.
  16. ^ a b Safi, Rachid; Bertrand, Stéphanie; Marchand, Oriane; Duffraisse, Marilyne; de Luze, Amaury; Vanacker, Jean-Marc; Maraninchi, Marie; Margotat, Alain; Demeneix, Barbara; Laudet, Vincent (1 February 2004). "The Axolotl (Ambystoma mexicanum), a Neotenic Amphibian, Expresses Functional Thyroid Hormone Receptors". Endocrinology. 145 (2): 760–772. doi:10.1210/en.2003-0913. PMID 14576183.
  17. ^ Pietsch, Paul; Schneider, Carl W. (1985). "Vision and the skin camouflage reactions of Ambystoma larvae: the effects of eye transplants and brain lesions". Brain Research. 340 (1): 37–60. doi:10.1016/0006-8993(85)90772-3. PMID 4027646. S2CID 22723238.
  18. ^ Frost, S. K. (1984). "The pigmentary system of developing axolotls. I. A biochemical and structural analysis of the wild-type pigment phenotype". J Embryol Exp Morphol. 81 (1): 105–125. PMID 6470605.
  19. ^ "18 Types of Axolotl Colors You Can Own (Axolotl Color Guide)". 14 August 2019.
  20. ^ a b Frost, Sally K.; Briggs, Fran; Malacinski, George M. (1984). "A color atlas of pigment genes in the Mexican axolotl (Ambystoma mexicanum)". Differentiation. 26 (1–3): 182–188. doi:10.1111/j.1432-0436.1984.tb01393.x.
  21. ^ a b c Nowoshilow, Sergej; Schloissnig, Siegfried; Fei, Ji-Feng; Dahl, Andreas; Pang, Andy W. C.; Pippel, Martin; Winkler, Sylke; Hastie, Alex R.; Young, George (24 January 2018). "The axolotl genome and the evolution of key tissue formation regulators". Nature. 554 (7690): 50–55. Bibcode:2018Natur.554...50N. doi:10.1038/nature25458. hdl:21.11116/0000-0003-F659-4. ISSN 1476-4687. PMID 29364872.
  22. ^ Weird Creatures with Nick Baker (Television series). Dartmoor, England, UK: The Science Channel. 11 November 2009.
  23. ^ Caballero-Pérez, Juan; Espinal-Centeno, Annie; Falcon, Francisco; García-Ortega, Luis F.; Curiel-Quesada, Everardo; Cruz-Hernández, Andrés; Bako, Laszlo; Chen, Xuemei; Martínez, Octavio; Alberto Arteaga-Vázquez, Mario; Herrera-Estrella, Luis (January 2018). "Transcriptional landscapes of Axolotl (Ambystoma mexicanum)". Developmental Biology. 433 (2): 227–239. doi:10.1016/j.ydbio.2017.08.022. PMID 29291975.
  24. ^ a b Sandoval-Guzmán, Tatiana (August 2023). "The axolotl". Nature Methods. 20 (8): 1117–1119. doi:10.1038/s41592-023-01961-5. ISSN 1548-7091. PMID 37553398. S2CID 260699417.
  25. ^ Vieira, Warren A.; Wells, Kaylee M.; McCusker, Catherine D. (2020). "Advancements to the Axolotl Model for Regeneration and Aging". Gerontology. 66 (3): 212–222. doi:10.1159/000504294. PMC 7214127. PMID 31779024.
  26. ^ Goodwin, James W.; Pinto, Alexander R.; Rosenthal, Nadia A. (4 June 2013). Olson, Eric N. (ed.). "Macrophages are required for adult salamander limb regeneration". Proceedings of the National Academy of Sciences of the United States of America. 110 (23): 9415–9420. Bibcode:2013PNAS..110.9415G. doi:10.1073/pnas.1300290110. PMC 3677454. PMID 23690624.
  27. ^ Pedersen, Katherine; Rasmussen, Rikke Kongsgaard; Dittrich, Anita; Pedersen, Michael; Lauridsen, Henrik (17 April 2020). "Modulating the immune response and the pericardial environment with LPS or prednisolone in the axolotl does not change the regenerative capacity of cryoinjured hearts". The FASEB Journal. 34 (S1): 1. doi:10.1096/fasebj.2020.34.s1.04015. S2CID 218792957.
  28. ^ a b c Kulbisky, Gordon P; Rickey, Daniel W; Reed, Martin H; Björklund, Natalie; Gordon, Richard (1999). "The axolotl as an animal model for the comparison of 3-D ultrasound with plain film radiography". Ultrasound in Medicine and Biology. 25 (6): 969–975. doi:10.1016/s0301-5629(99)00040-x. PMID 10461726.
  29. ^ Adamson, Carly J.; Morrison-Welch, Nikolas; Rogers, Crystal D. (June 2022). "The amazing and anomalous axolotls as scientific models". Developmental Dynamics. 251 (6): 922–933. doi:10.1002/dvdy.470. ISSN 1097-0177. PMC 9536427. PMID 35322911.
  30. ^ Boron, Walter F.; Boulpaep, Emile L. (2012). "49. Synthesis of Thyroid Hormones". Medical Physiology (2nd ed.). Elsevier/Saunders. p. 1044. ISBN 978-1-4377-1753-2.
  31. ^ Swingle, W. W. (November 1923). "Iodine and Amphibian Metamorphosis". The Biological Bulletin. 45 (5): 229–253. doi:10.2307/1536749. JSTOR 1536749.
  32. ^ Ingram, W. R. (1 December 1928). "Metamorphosis of the Colorado Axolotl by Injection of Inorganic Iodine". Experimental Biology and Medicine. 26 (3): 191. doi:10.3181/00379727-26-4212.
  33. ^ Dvoskin, Samuel (May 1947). "The Thyroxine-Like Action of Elemental Iodine in the Rat and Chick1". Endocrinology. 40 (5): 334–352. doi:10.1210/endo-40-5-334. PMID 20245954.
  34. ^ Krylov, O. A. (January 1961). "The role of haloids (bromine and iodine) in the metamorphosis of amphibia". Bulletin of Experimental Biology and Medicine. 50 (1): 724–727. doi:10.1007/BF00796048.
  35. ^ Ley, Willy (February 1968). "Epitaph for a Lonely Olm". For Your Information. Galaxy Science Fiction. pp. 95–104.
  36. ^ Malacinski, George M. (1 May 1978). "The Mexican Axolotl, Ambystoma mexicanum: Its Biology and Developmental Genetics, and Its Autonomous Cell-lethal Genes". American Zoologist. 18 (2): 195–206. doi:10.1093/icb/18.2.195.
  37. ^ Crowner, Anne; Khatri, Shivam; Blichmann, Dana; Voss, S. Randal (12 April 2019). "Rediscovering the Axolotl as a Model for Thyroid Hormone Dependent Development". Frontiers in Endocrinology. 10 237. doi:10.3389/fendo.2019.00237. PMC 6473073. PMID 31031711.
  38. ^ a b c d Lazcano, I.; Olvera, A.; Pech-Pool, S. M.; Sachs, L.; Buisine, N.; Orozco, A. (10 July 2023). "Differential effects of 3,5-T2 and T3 on the gill regeneration and metamorphosis of the Ambystoma mexicanum (axolotl)". Frontiers in Endocrinology. 14 1208182. doi:10.3389/fendo.2023.1208182. ISSN 1664-2392. PMC 10364608. PMID 37492199.
  39. ^ Demircan, Turan; Ovezmyradov, Guvanch; Yıldırım, Berna; Keskin, İlknur; İlhan, Ayşe Elif; Fesçioğlu, Ece Cana; Öztürk, Gürkan; Yıldırım, Süleyman (20 July 2018). "Experimentally induced metamorphosis in highly regenerative axolotl (Ambystoma mexicanum) under constant diet restructures microbiota". Scientific Reports. 8 (1): 10974. Bibcode:2018NatSR...810974D. doi:10.1038/s41598-018-29373-y. PMC 6054665. PMID 30030457.
  40. ^ Gale, Jen (5 November 2025). "What happens if an axolotl larva is placed in water containing sufficient iodine?". The Institute for Environmental Research and Education. Retrieved 1 December 2025.
  41. ^ a b "Axolotls – Metamorphosed & Tiger Salamanders". axolotl.org. Retrieved 25 January 2022.
  42. ^ Brown, Donald D. (25 November 1997). "The role of thyroid hormone in zebrafish and axolotl development". Proceedings of the National Academy of Sciences. 94 (24): 13011–13016. Bibcode:1997PNAS...9413011B. doi:10.1073/pnas.94.24.13011. PMC 24254. PMID 9371791.
  43. ^ Woodcock, M. Ryan; Vaughn-Wolfe, Jennifer; Elias, Alexandra; Kump, D. Kevin; Kendall, Katharina Denise; Timoshevskaya, Nataliya; Timoshevskiy, Vladimir; Perry, Dustin W.; Smith, Jeramiah J.; Spiewak, Jessica E.; Parichy, David M.; Voss, S. Randal (31 January 2017). "Identification of Mutant Genes and Introgressed Tiger Salamander DNA in the Laboratory Axolotl, Ambystoma mexicanum". Scientific Reports. 7 (1): 5. Bibcode:2017NatSR...7....6W. doi:10.1038/s41598-017-00059-1. ISSN 2045-2322. PMC 5428337. PMID 28127056.
  44. ^ "Mexican Walking Fish, Axolotls Ambystoma mexicanum" (PDF). Archived from the original (PDF) on 15 March 2018.
  45. ^ "Axolotols (Walking Fish)". Aquarium Online. Archived from the original on 10 April 2013. Retrieved 12 September 2013.
  46. ^ Shaffer, H. Bradley (December 1993). "Phylogenetics of Model Organisms: The Laboratory Axolotl, Ambystoma mexicanum". Systematic Biology. 42 (4): 508–522. doi:10.2307/2992486. JSTOR 2992486.
  47. ^ a b Dunning, Hayley (29 August 2025). "Axolotls: Meet the amphibians that never grow up". nhm.ac.uk. Archived from the original on 1 October 2025. Retrieved 30 November 2025.
  48. ^ "Lake Xochimilco, Borough of Xochimilco in southern México City, 162 L • Biotope Aquarium". Biotope Aquarium. Retrieved 30 April 2021.
  49. ^ a b c Majchrzak, Amy (21 June 2004). "Ambystoma mexicanum (Salamandra ajolote)". Animal Diversity Web.
  50. ^ AmphibiaWeb 2025 Ambystoma mexicanum: Mexican Axolotl <https://amphibiaweb.org/species/3842> University of California, Berkeley, CA, USA. Accessed May 9, 2026.
  51. ^ AmphibiaWeb 2025 Ambystoma mexicanum: Mexican Axolotl <https://amphibiaweb.org/species/3842> University of California, Berkeley, CA, USA. Accessed May 9, 2026.
  52. ^ Wainwright, P. C.; Sanford, C. P.; Reilly, S. M.; Lauder, G. V. (1989). "Evolution of motor patterns: aquatic feeding in salamanders and ray-finned fishes". Brain, Behavior and Evolution. 34 (6): 329–341. doi:10.1159/000116519. PMID 2611639.
  53. ^ Stevenson, Mark (28 January 2014). "Mexico's 'water monster' may have disappeared". SFGate. Mexico City. Associated Press. Archived from the original on 30 January 2014. Retrieved 29 January 2014.
  54. ^ Gander, Kashmira (24 February 2014). "Endangered 'water monster' Axolotl found in Mexico City lake". The Independent. Retrieved 2 June 2017.
  55. ^ Nandini, Sarma; García, Pedro Ramirez; Sarma, S. S. S. (2016). "Water quality in Lake Xochimilco, Mexico: zooplankton indicators and Vibrio cholerae". Journal of Limnology. 75 (1). doi:10.4081/jlimnol.2015.1213. ISSN 1723-8633.
  56. ^ Robles-Mendoza, C.; García-Basilio, C.; Cram-Heydrich, S.; Hernández-Quiroz, M.; Vanegas-Pérez, C. (1 February 2009). "Organophosphorus pesticides effect on early stages of the axolotl Ambystoma mexicanum (Amphibia: Caudata)". Chemosphere. 74 (5): 703–710. Bibcode:2009Chmsp..74..703R. doi:10.1016/j.chemosphere.2008.09.087. ISSN 0045-6535. PMID 19012946.
  57. ^ Parra-Plea, G; Zamudio, K.R.; Recuero, E.; Aguilar-=Miguel, X.; Huaxuz, D.; Zambrano, L. (2011). "Conservation genetics of threatened Mexican axolotls (Ambystoma)". Animal Conservation. 15 (1): 61–72. doi:10.1111/j.1469-1795.2011.00488.x. S2CID 46992721.
  58. ^ Woodcock, M. Ryan; Vaughn-Wolfe, Jennifer; Elias, Alexandra; Kump, D. Kevin; Kendall, Katharina Denise; Timoshevskaya, Nataliya; Timoshevskiy, Vladimir; Perry, Dustin W.; Smith, Jeramiah J.; Spiewak, Jessica E.; Parichy, David M.; Voss, S. Randal (31 January 2017). "Identification of Mutant Genes and Introgressed Tiger Salamander DNA in the Laboratory Axolotl, Ambystoma mexicanum". Scientific Reports. 7 (1): 6. Bibcode:2017NatSR...7....6W. doi:10.1038/s41598-017-00059-1. ISSN 2045-2322. PMC 5428337. PMID 28127056.
  59. ^ "Mexico City's 'water monster' nears extinction". U.S. Water News Online. November 2008. Archived from the original on 23 July 2011. Retrieved 28 June 2010.
  60. ^ Alcaraz, Guillermina; López-Portela, Xarini; Robles-Mendoza, Cecilia (1 July 2015). "Response of a native endangered axolotl, Ambystoma mexicanum (Amphibia), to exotic fish predator". Hydrobiologia. 753 (1): 73–80. Bibcode:2015HyBio.753...73A. doi:10.1007/s10750-015-2194-4. ISSN 1573-5117. S2CID 254550469.
  61. ^ Walker, Matt (26 August 2009). "Axolotl verges on wild extinction". BBC News. Retrieved 28 June 2010.
  62. ^ "Are Axolotls Endangered? You Need To Be Careful..." PetAquariums.com. 22 April 2020. Archived from the original on 26 June 2021. Retrieved 26 June 2021.
  63. ^ Ramos, A.G.; Mena-Gonzalez, H.; Zambrano, L (2021). "The potential of temporary shelters to increase survival of the endangered Mexican axolotl". Aquatic Conservation: Marine and Freshwater Ecosystems. 31 (6): 1535–1542. Bibcode:2021ACMFE..31.1535R. doi:10.1002/aqc.3520. S2CID 235587173.
  64. ^ Paúl, María Luisa (1 December 2023). "Mexico wants you to adopt an axolotl, the amphibian that never grows up". Washington Post. ISSN 0190-8286. Retrieved 1 December 2023.
  65. ^ Ramos, Alejandra G.; Horacio Mena; David Schneider; Luis Zambrano (30 April 2025). "Movement ecology of captive-bred axolotls in restored and artificial wetlands: Conservation insights for amphibian reintroductions and translocations". PLOS One. 20 (4) e0314257. Bibcode:2025PLoSO..2014257R. doi:10.1371/journal.pone.0314257. PMC 12043180. PMID 40305450.
  66. ^ Fink, Kathryn (6 May 2025). "Good news for the adorable axolotl — ones born in captivity could survive in the wild". npr.org. NPR. Retrieved 12 May 2025.
  67. ^ Gill, Victoria (30 April 2025). "Endangered axolotl release raises hopes for rare amphibian". BBC News. Retrieved 12 May 2025.
  68. ^ Tickell, Sofia Castello Y. (30 October 2012). "Mythic Salamander Faces Crucial Test: Survival in the Wild". The New York Times. Archived from the original on 25 March 2016. Retrieved 30 July 2015.
  69. ^ Voss, S. Randal; Woodcock, M. Ryan; Zambrano, Luis (December 2015). "A Tale of Two Axolotls". BioScience. 65 (12): 1134–1140. doi:10.1093/biosci/biv153. PMC 7051018. PMID 32123398.
  70. ^ Huxley, Julian S. (January 1920). "Metamorphosis of Axolotl caused by Thyroid-feeding". Nature. 104 (2618): 435. Bibcode:1920Natur.104..435H. doi:10.1038/104435b0. ISSN 1476-4687.
  71. ^ Reiß, Christian; Olsson, Lennart; Hoßfeld, Uwe (2015). "The history of the oldest self-sustaining laboratory animal: 150 years of axolotl research". Journal of Experimental Zoology Part B: Molecular and Developmental Evolution. 324 (5): 393–404. Bibcode:2015JEZB..324..393R. doi:10.1002/jez.b.22617. ISSN 1552-5015. PMID 25920413.
  72. ^ Meyer, Sophie; Lauridsen, Henrik; Pedersen, Kathrine; Andersson, Sofie Amalie; van Ooij, Pim; Willems, Tineke; Berger, Rolf M. F.; Ebels, Tjark; Jensen, Bjarke (28 November 2022). "Opportunities and short-comings of the axolotl salamander heart as a model system of human single ventricle and excessive trabeculation". Scientific Reports. 12 (1): 20491. Bibcode:2022NatSR..1220491M. doi:10.1038/s41598-022-24442-9. ISSN 2045-2322. PMC 9705478. PMID 36443330.
  73. ^ Gordon, R. (1985). "A review of the theories of vertebrate neurulation and their relationship to the mechanics of neural tube birth defects". Journal of Embryology and Experimental Morphology. 89 (Supplement): 229–255. PMID 3913733.
  74. ^ Armstrong, John B. (1985). "The axolotl mutants". Developmental Genetics. 6 (1): 1–25. doi:10.1002/dvg.1020060102.
  75. ^ Roy, S; Gatien, S (November 2008). "Regeneration in axolotls: a model to aim for!". Experimental Gerontology. 43 (11): 968–73. doi:10.1016/j.exger.2008.09.003. PMID 18814845. S2CID 31199048.
  76. ^ Masselink, Wouter; Tanaka, Elly M. "Toward whole tissue imaging of axolotl regeneration". Developmental Dynamics. 250 (6): 800–806. doi:10.1002/dvdy.282. PMC 8247021. PMID 33336514.
  77. ^ Lust, Katharina; Tanaka, Elly M. (11 March 2025). "Adeno-associated viruses for efficient gene expression in the axolotl nervous system". Proceedings of the National Academy of Sciences. 122 (10) e2421373122. Bibcode:2025PNAS..12221373L. doi:10.1073/pnas.2421373122. ISSN 0027-8424. PMC 11912378. PMID 40042904.
  78. ^ "Axolotls – Requirements & Water Conditions in Captivity". axolotl.org. Retrieved 14 March 2016.
  79. ^ "Caudata Culture Species Entry – Ambystoma mexicanum – Axolotl". caudata.org. Archived from the original on 15 March 2016. Retrieved 14 March 2016.
  80. ^ "Axolotl Care" (PDF). Royal Veterinary College. Retrieved 20 May 2026.
  81. ^ Cirit, Şeyma S.; Deniz, Şinasi B.; Cirit, Burhan; Bayraktar, Abdulahad (May 2025). "Management of Hydrocoelom in an Axolotl (Ambystoma mexicanum)". Veterinary Medicine and Science. 11 (3). doi:10.1002/vms3.70373. PMC 13045757. PMID 40387063. S2CID 278730230. Retrieved 20 May 2026.
  82. ^ Wiegert, Joshua. "Axolotls: Keeping a Water Monster".
  83. ^ Strecker, Angela L.; Campbell, Philip M.; Olden, Julian D. (2011). "The Aquarium Trade as an Invasion Pathway in the Pacific Northwest". Fisheries. 36 (2): 74–85. Bibcode:2011Fish...36...74S. doi:10.1577/03632415.2011.10389070.
  84. ^ a b Pough, F. H. (1992). "Recommendations for the Care of Amphibians and Reptiles in Academic Institutions". Washington, D.C.: National Academy Press.
  85. ^ Clayton, Leigh Ann; Gore, Stacey R. (2007). "Amphibian Emergency Medicine". Veterinary Clinics of North America: Exotic Animal Practice. 10 (2): 587–620. doi:10.1016/j.cvex.2007.02.004. PMID 17577564.
  86. ^ Gresens, Jill (2004). "An Introduction to the Mexican Axolotl (Ambystoma mexicanum)". Lab Animal. 33 (9): 41–47. doi:10.1038/laban1004-41. PMID 15457201. S2CID 33299160.
  87. ^ Wings, O A review of gastrolith function with implications for fossil vertebrates and a revised classification Archived 4 March 2016 at the Wayback Machine Acta Palaeontologica Polonica 52 (1): 1–16
  88. ^ Gordon, N, Gastroliths – How I Learned to Stop Worrying and Love Gravel. Archived 22 September 2020 at the Wayback Machine
  89. ^ Björklund, N.K. (1993). Small is beautiful: economical axolotl colony maintenance with natural spawnings as if axolotls mattered. In: Handbook on Practical Methods. Ed.: G.M. Malacinski & S.T. Duhon. Bloomington, Department of Biology, Indiana University: 38–47.
  90. ^ Loh, Richmond (15 May 2015). "Common Disease Conditions in Axolotls". Vin.com. Archived from the original on 4 August 2020. Retrieved 21 January 2022.
  91. ^ Clare, John P. "Health and Diseases". axolotl.org.
  92. ^ "Transition & Feeding". Morphed Axolotls. Archived from the original on 31 March 2023.
  93. ^ a b c d Garcia, David Alire (20 November 2018). "Mexico's axolotl, a cartoon hero and genetic marvel, fights for survival". Reuters. Retrieved 16 August 2022.
  94. ^ "Mexican axolotl will be the new image of the 50 peso bill". The Yucatan Times. 21 February 2020. Archived from the original on 10 February 2025. Retrieved 24 April 2025.
  95. ^ "Billete de 50 pesos de la familia G". banxico.org.mx (in Spanish). Retrieved 20 February 2023.
  96. ^ "Banknote of 2021 Nominations". theibns.org. Retrieved 20 February 2023.
  97. ^ Graham, Thomas (21 November 2025). "A lot of axolotls: the amphibian-themed banknote Mexicans don't want to spend". The Guardian. Retrieved 22 May 2026.
  98. ^ Kojima, Akira (28 June 2021). "神戸新聞NEXT|連載・特集|話題|「ウーパールーパー」を覚えていますか "昭和"に一世風靡した不思議な生き物、今もペットとして根強い人気". kobe-np.co.jp (in Japanese). Retrieved 20 March 2026.
  99. ^ Adamson, Carly J.; Morrison‐Welch, Nikolas; Rogers, Crystal D. (April 2022). "The amazing and anomalous axolotls as scientific models". Developmental Dynamics. 251 (6): 922–933. doi:10.1002/dvdy.470. ISSN 1058-8388. PMC 9536427.
  100. ^ Renard, Jean-Bruno (February 2010). "L'axolotl. De la controverse scientifique au mythe littéraire". Cairn.info. 108 (2): 19–32. doi:10.3917/soc.108.0019. Archived from the original on 15 March 2023. Retrieved 15 February 2026.
  101. ^ Minecraft (3 October 2020). ""Minecraft Live: Caves & Cliffs – First Look"". YouTube. "And then we also found out that axolotls are endangered in the real world, and we think it's good to add endangered animals to Minecraft to create awareness about that." – Agnes Larsson
  102. ^ "The Guardian Battle 21180". lego.com. Retrieved 20 February 2023.
  103. ^ "The Axolotl House 21247". lego.com. Retrieved 27 December 2024.
  104. ^ "Axolotl: The Real Julio Cortazar". hum11c.omeka.fas.harvard.edu. Harvard University. Retrieved 4 June 2025.
  105. ^ "Axolotl, Xolotl, and Religion". hum11c.omeka.fas.harvard.edu. Harvard University. Retrieved 4 June 2025.
  106. ^ "Approved names". nameexoworlds.iau.org. Retrieved 2 January 2020.
  107. ^ "100 000s of People from 112 Countries Select Names for Exoplanet Systems In Celebration of IAU's 100th Anniversary". International Astronomical Union. 17 December 2019. Retrieved 2 January 2020.
[edit]