Axolotl: Types and colours

Axolotl: Types and colours

If you’re interested in learning about different types of axolotls, you’ve come to the right place. In this blog post, we’ll be discussing the various axolotl types, their physical appearance, and their habitat. Axolotls are a type of salamander that is native to Mexico. They are commonly found in lakes and canals in and around Mexico City. Axolotls are unique creatures that have the ability to regenerate their limbs and other body parts.

Axolotl Types

The axolotl types can be roughly divided into four categories:

1. Albinos

2. Coppers

3. Whites (Leucistic)

4. Wildlings (Melanoid)

Axolotl Albinos

Albinos are white or yellowish and can also be somewhat shiny or shimmery. Their eggs are white. Due to an enzyme defect, albinos do not have melanin, which would otherwise c a use a darker colouration. The enzyme that albinos do not have is tyrosinase (amino acid = tyrosine).

Axolotl Coppers

Coppers come in many colours, such as yellow, brown, white, copper. They can also shimmer a little. Their eggs are beige/light brown. In contrast to the albinos, they do have tyrosine or tyrosinase, but they do not produce melanin either, only phaeomelanin. Phaeomelanin is a pigment which, together with eumelanin (also a pigment), determines the colour of t he skin.

Axolotl Wildlings

Wildlings (melanonids) are usually black and/or brown. Sometimes a yellowish colouration occurs. Their eggs are also dark.

The colour of the eggs does not (always) indicate what the larva will look like later. The colour of the eggs depends on the colour of the mother. However, the colouration of the emerging larva does not depend on the mother alone, but on both parents.

Unfortunately, in some countries axolotls have been dyed or given colour pigments so that they “shine” in numerous bright colours (red, pink, green etc.). It is not advisable to buy a dyed animal.

Like all amphibians, the “normal” axolotl has three kinds of cells responsible for the pigmentation of the skin and eyes, the chromatophores.

The melanophores carry pigments (melanin and others) responsible for black and brown colors The xanthophores carry the yellow color The iridiophores are pigmentary cells that reflect light .

There were already animals in the wild that showed a different color (or lack of color) from the usual wild type: pink axolotls were among the animals brought back to the Museum in 1863, which are largely (but not exclusively, as is sometimes said) the ancestors of our domestic axolotls. It is also known that the diversification of colors and coats is one of the first consequences of the domestication of a species.

The main genetic mutations determining the appearance of forms of different color are albinism, xanthism.

Albinism corresponds to the absence of black pigment, or to a very reduced production of them by the organism. In true albinism, the total absence of pigment, the eyes are pink. Albinism is genetically associated with many malformations (especially the absence of eyes) in some species, which makes the embryos not viable, and this i s probably also the case in the axolotl. Where possible, albino juveniles are more fragile and vulnerable than juveniles with wild-type coloration and suffer higher mortality rates at all stages of development. They are more easily spotted by predators and are less efficient at foraging due to their poor eyesight. They are also more susceptible to cellular dysfunction and more susceptible to disease. This is why a “marriage” likely to produce, in the same egg-laying, pigmented larvae and albinos in proportions predictable from the genetic probabilities usually results in an effective number of albinos lower than expected.

The pink axolotls common in captivity (which are in fact white, it is their red blood that makes them look pink) are not albinos in the strict sense, but partial albinos. The scientific term is leucistic. Their eyes are pigmented and they can show localized traces of pigmentation, usually on the gill racks and on the top of the head. 

The full albino axolotl exists in captivity, however, it is the result of genetic manipulation in the laboratory. It is a hybrid, more exactly a “chimera”. The American biologist Humphrey succeeded in the 1960s in transferring in vitro the gene of albinism taken from a female of Ambystoma tigrinum into the genome of an axolotl. The eggs developed into adult axolotl and their offspring proved to be stable in their characters and fertile, even after crossing with ordinary axolotls, although the breeding is more delicate. The neoteny is preserved. There are two forms of this type, the full albino and the “gold” axolotl. The first one is completely depigmented. The axolotl “gold” is completely devoid of melanophores, with red eyes. However, the xanthofores are present in attenuated form, as the melanophores were present in attenuated form in the leucistic axolotl and the animal has a more or less yellow coloration.

The leucistic mutation and albinism are called recessive. That is to say that their effects are manifested on the color of the animal – we say that the gene is expressed – only if the mutant gene is present TWICE on the allele formed by the two chromosomes (homozygous), therefore if it was transmitted by the father AND by the mother. When it is present only once (heterozygous), the animal is genetically carrier without affecting its appearance (phenotype). It can always be transmitted to its descendants. It follows that:

  • Two mutant animals that are both pink, gold or albino only give mutant offspring: all pink, gold or albino, depending on the gene of the parents (homozygous mutants).
  • Two animals without the mutant gene give only offspring resembling the parents (pigmented), not carriers (homozygous pigmented).
  • Two parents of which one is a carrier of the gene and the other one is not, give only first generation offspring resembling the parents, pigmented, of which a part (50%) remain carriers of the gene (heterozygous mutants).
  • Two parents who carry the gene without showing it give first generation offspring: for a quarter mutant (homozygous), for another quarter pigmented, non-carriers, and for half pigmented but carrying the gene (heterozygous mutants).

This is the simplest case because it involves only two cases, the presence or absence of mutation on a single gene, for a single color. Insofar as we can have several colors in play (melanophores and xanthophores), with variants of these, where some colorations involve several genes, and where a given genetic profile can lead to animals externally quite different from each other, for example, depending on the degree of pigmentation expressed in a leucistic axolotl, there are other forms of colorations. Hobbyists continue to select these and try to develop new ones, without genetic manipulation, by choosing the breeding stock in such a way as to strengthen this or that trait present in the parents.

All Axolotl Types

In the end, we distinguish the following types, some of which are quite rare:

  • Wild type (grey-black pigmented, melanophores, xanthophores and Iridiophores)
  • Copper: Copper is a pigmented form with another color than the wild type, brown rather than gray, i.e. brown spots on a copper background; It is a rather rare color whose genetics is not completely elucidated. We do not know if it is a spontaneous color already present in the genetic heritage of the wild axolotl, a form that appeared spontaneously in captivity (mutation) and then retained by selection, or a hybridization. The reproduction of the “copper” is often laborious, all the eggs are not viable, clearly because of genetic problems. This may be due to hybrid inheritance or to excessive inbreeding as a result of inbreeding to fix the strain. It would be necessary to enlarge the gene pool by introducing wild type animals. 
  • Leucistics (melanophore inhibition). Animals that have visible melanophores, although inhibited overall, are said to be harlequin. A harlequin is genetically leucistic (homozygous for partial albinism), but it can carry the genes for other colors.
  • Gold (inhibition of xanthophores) White albino: no pigment, the animal is both albino (without melanophores) and axanthic (without xanthophores)
  • Melanic : pigmented animals but without iriodophores, which means for example that the eyes are without a golden circle around the pupil and that their coat tends to be more plain. They can exist in different colors and their gradations: Black, Grey, White, Gold, Albino or Copper.

Is the Axolotl an Endangered Species? 

There have always been a few natural threats to the Axolotl’s survival, including predatory birds like herons.

More recently, however, Axolotls have begun to suffer from the introduction of large numbers of fish, like carp, into their lake habitat. These fish compete with Axolotls for food and also eat Axolotl eggs.

Herons are natural predators of the Axolotl. The Axolotl population has decreased as a result.

Axolotls are also popular as pets and as food. Roasted Axolotl is a festive treat in Mexico.

All these factors have had the effect of further shrinking Axolotl numbers in the wild. They are now considered a critically endangered species – a species likely to become extinct. 

Their popularity as pets, however, means that despite the challenges they face in the wild, Axolotls continue to thrive. Even if they can no longer be found in their natural habitat one day, we will still be able to enjoy them in captivity for many years to come.


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