Axolotl Color Morphs Guide

"Dirty" freckled leucistic copper axolotl. All copper axolotls have red pupils that may be more visible when light is shined on them! Credit: Rainy Day Aquatics.

Axolotl Color Morphs Introduction

This guide describes the differences between each axolotl color morph and provides images to go along with them!

Here are a few terms we will be using in this article to describe the differences between the axolotl color morphs! Before reading on, it may be helpful to familiarize yourself with the following terms:

Melanin: Brown/black pigment

Pheomelanin: Responsible for red, yellow, and pink hues

Melanophore: Cell that contains melanin

Xanthophores: Responsible for yellow pigmentation

Iridophore: Pigments that reflect lightEumelanin - The most common form of melanin; brown/black pigment

Wild type axolotl. Credit: Rainy Day Aquatics.

Greenish wild type axolotl. Credit: Rainy Day Aquatics.

Wild Type

The term "wild type" is used to refer to the most common characteristic of a species under natural conditions, without displaying any defining genetic mutations. Wild type axolotls are typically brownish/greyish and can sometimes have a slightly greenish tint. Wild type axolotls will always have a gold eye ring surrounding a black pupil. They contain melanophores, xanthophores, and iridophores.

Note: The most surefire way to distinguish wild types from copper axolotls is the fact that all copper axolotls will have a red pupil when light is shined on it, while wild type pupils will stay black.

This leucistic axolotl has a shiny eye ring. Most leucistic axolotls will not have this unless they have a high concentration of iridiphores (shiny pigments). Photo credit: Rainy Day Aquatics.

This leucistic axolotl is called a "dirty leucistic" because of the dark pigmentation found above the midline of its body and on its face. It is uncommon for leucisitc axolotls to have this much dark pigment. Photo credit: Rainy Day Aquatics.

This leucistic axolotl is called a "dirty leucistic" because of the dark pigmentation found above the midline of its body and on its face. Photo credit: Rainy Day Aquatics.

This leucistic axolotl is called a "blue gilled" leucistic because the dark pigment around the gills appears to have a bluish hue. Blue gilled leucistics are less common. Photo credit: Rainy Day Aquatics.

Leucistic (White)

Leucism is a genetic mutation which causes white, pale, or patchy coloration in skin, hair, and nails but not the eyes. In axolotls this is caused by a damaged or missing version of Edn3, a gene that codes the protein Endothelin-3 that tells the chromatophores to migrate from the neural crest and spread across the body as an embryo. 

Leucism in axolotls presents as a white/pinkish body that still has pigmented eyes with xanthophores and melanophores. A normal leucistic will have no melanin on its body other than its eyes, while "dirty leucistic" will have scattered melanin on their face and back. A leucistic axolotl with more melanin on the gill stalks than normal are known as "dark-gilled leucistics".

Golden albino axolotls often have noticeable iridophores (shiny pigment) on the body and eye rings. Photo credit: Rainy Day Aquatics.

Albino (Golden Albino)

Albinism is a genetic mutation that results in a partial or complete absence in skin pigment. Albinism in axolotls results in the loss of melanophores. However, xanthophores are still present, resulting in their yellow coloration. Albino axolotls can also have iridophores.

Melanoid axolotl. Photo credit: Rainy Day Aquatics.

Melanoid axolotl. Photo credit: Rainy Day Aquatics.

Melanoid axolotl. Photo credit: Rainy Day Aquatics.

Melanoid

Melanoid axolotls completely lack iridophores and some xanthophores. This results in increased melanophores (dark coloration) on the whole body, as opposed to only scattered spots in wild types and other morphs. This causes melanoid axolotls to have very few spots.

Note: Melanoid and Axanthic are the only two morphs that can never have iridophores or eye rings.

This copper axolotl has a shiny eye ring, which means it has a higher concentration of iridophores (shiny pigments) in the eyes. Photo credit: Rainy Day Aquatics.

Copper

Copper is a form of albinism, resulting in partial loss of pigment. Copper axolotls lack the enzyme, Tyrosinase, that normally oxidizes pheomelanin (responsible for red pigmentation) into eumelanin (responsible for dark coloration). Without this enzyme, they are unable to "convert" red pigmentation into darker pigmentation.

This results in their spots of orange pigmentation, rather than the dark brown spots of a wild type. It also results in their inability to produce fully black pupils, thus resulting in their characteristic red reflective ones. Copper axolotls may have iridophores.

Note: The most surefire way to distinguish wild types from copper axolotls is the fact that all copper axolotls will have a red pupil when light is shined on it, while wild type pupils will stay black.

Axanthic axolotls look different than wild types because they typically have no yellowish color, making them look more grey. Photo credit: Rainy Day Aquatics.

Axanthic axolotl with a greyish coloration. Photo credit: Rainy Day Aquatics.

Axanthic

Axanthicism is a genetic mutation that causes animals to be unable or only partially able to produce xanthophores (yellow pigments). In axolotls, axanthicism results in a loss of xanthophores and iridophores. This results in their characteristic greyish color, along with spots of melanophores (dark pigments) all over the body. Axanthics only very rarely have a reflective eye ring. Axanthic axolotls will show face fluorescence, which can be seen as the connective tissue in their head and limb joints glowing green under blue/black light.

Note: Melanoid and axanthic are the only two morphs which almost never have reflective eye rings

Hypomelanistic axolotl. Photo credit: Rainy Day Aquatics.

Hypomelanistic

Hypomelanistic, or "hypo" for short, is the newest morph discovered in axolotls!

The hypomelanistic gene causes axolotls to produce much less melanin than usual. Xanthophores and iridophores are unaffected, however, which causes these axolotls to appear as a yellowish color. 

GFP axolotl with glowing green eyes under black light. Photo credit: Rainy Day Aquatics.

Green Fluorescent Protein (GFP)

GFP axolotls were first modified in the lab, where fluorescent jellyfish genes were inserted into their genome. After this, the genes were then able to be passed down through breeding, thus giving us all the GFP axolotls we see today. The GFP gene enables the axolotl to absorb short wavelengths of light, like blue and black light, and emit green light as a result. This causes GFP axolotls to glow green under blue and black light.

Two Gene Variations

White albino axolotl. Photo credit: Rainy Day Aquatics.

This white albino axolotl has a shiny eye ring, due to having a higher concentration of iridophores in the eyes, which is less common. Photo credit: Rainy Day Aquatics.

White Albino

White albino axolotls will have a complete lack of melanophores, iridophores, and have a damaged or missing Edn3 gene, which prevents the chromatophores from spreading from the neural crest. Due to this, xanthophores can only be present on the gills and down the spine. 

White Axanthic

White axanthic axolotls will have a complete lack of xanthophores and only have melanophores in the eyes and gill stalks. They can potentially have iridophores in the eyes. 

Leucistic copper axolotl. All copper axolotls have a red pupil that is more easily visible under bright light! Photo credit: Rainy Day Aquatics

Leucistic Copper

Leucistic copper axolotls will have light eyes and a red pupil. If the axolotl is "dirty", its dark spots would be a chocolate brown color instead of black. 

The only real distinguishing coloration a melanoid albino axolotl can have is a yellow color on their face or top half of their body. This is less common however. Photo credit: Rainy Day Aquatics

This melanoid albino axolotl is another strong example of the yellow coloration that they can have. However, this coloration is less common. Photo credit: Rainy Day Aquatics

Melanoid Albino

Melanoid albino axolotls lack melanin, iridophores, and have a reduced amount of xanthophores. The resulting color is a slight yellow tint. 

Melanoid Axanthic

Sometimes referred to as “lavenders” by breeders, melanoid axanthic axolotls appear to have a purple-ish tint at a very young age. However, most morphs will darken significantly as they age, and melanoid axanthic axolotls will end up with a darker color, like a dark melanoid or wild type axolotl in adulthood. These axolotls lack xanthophores and iridophores, but have a dense distribution of melanophores.

Melanoid copper axolotl. Photo credit: Rainy Day Aquatics

Melanoid Copper

Melanoid axolotls have almost a complete lack of iridophores and produce pheomelanin. Due to the melanoid gene, they would have little if any spots.

Albino axanthic axolotl. Photo credit: Rainy Day Aquatics

Albino Axanthic

Albino axanthic axolotls would have a complete lack of melanophores and xanthophores, causing them to be fully white. Keep in mind that over time axanthics gain yellow pigment due to their diet.

Axanthic copper with lighter coloration. Photo credit: Rainy Day Aquatics

Axanthic copper axolotl with darker coloration. Photo credit: Rainy Day Aquatics

Axanthic Copper

Albino axanthic axolotls would have a complete lack of melanophores and xanthophores, causing them to be fully white. Keep in mind that over time axanthics gain yellow pigment due to their diet.

This is a golden albino axolotl that would look indistinguishable from an albino copper axolotl. Photo credit: Rainy Day Aquatics

Albino Copper

Appearance is indistinguishable from Albino (Golden albino).

Hypomelanistic copper axolotl. Photo credit: Rainy Day Aquatics

Hypomelanistic Copper

Hypomelanistic melanoid axolotl. Photo credit: Rainy Day Aquatics

Hypomelanistic Melanoid

Three Gene Variations

Melanoid axanthic copper (MAC) axolotl. Credit: Rainy Day Aquatics

Melanoid axanthic copper (MAC) axolotl. Credit: Rainy Day Aquatics

Melanoid Axanthic Copper

Melanoid axanthic coppers, often referred to as MACs, possess all three of these recessive morph genes. MACs and melanoid coppers are nearly indistinguishable, except for at a young age when the skin cells are more easily observable. At a young age, it will be apparent that MACs lack yellow xanthophores, while melanoid coppers do have them.

​MACs are usually sought after for breeding purposes, since they have melanoid, axanthic, and copper genes which allow it to easily produce a high number of favorable offspring when paired with another melanoid, axanthic, or copper axolotl.

Axanthic albino axolotl. Credit: Rainy Day Aquatics

Albino Combinations

The following albino three gene combinations are indistinguishable from white melanoid albino axolotls:

White Melanoid Albino

White Albino Axanthic

White Albino Copper

Melanoid Albino Axanthic

Melanoid Albino Copper

Other Phenotypes

This split mosaic axolotl shows two entirely different morphs in one body (leucistic and wild type)! Credit: Rainy Day Aquatics

Mosaic

Mosaicism is a genetic mutation that takes place during the embryonic development of the axolotl egg. As the egg cell first begins to divide into more cells, a specific error occurs, resulting in the coding of two sets of dominant genes in one body, which often results in two different morph colors on one body as well.

The earlier that this mutation takes place during the development of the egg, the more split the coloration will appear on the axolotl. For example, the mutation occurring during only the first couple divisions of the egg will result in an axolotl with almost completely split coloration. When the mutation occurs later on, then the resulting axolotl will have a more mottled appearance in coloration.

Interestingly, almost all mosaic axolotls turn out to be male! The exact reason to this is not yet known.

Mosaic axolotls can mate and reproduce, but the offspring will not be mosaic like the parent, and will most likely all be normal axolotl morphs.

Non-albino golden (NAG) axolotls usually have a shiny eye ring, light yellow or tan body coloration with black spots, and a black tail tip. Photo credit: @reiya.exe

Non-albino Golden

Non-albino golden (aka NAG) axolotls are a type of mosaic axolotl, resulting from a certain mutation occurring during the cell division of the developing axolotl egg.

NAGs can be characterized by their shiny reflective irises, reflective gill iridophores, black tail tip, light yellow/tan body coloration, uneven pigmentation, and often black spots. They are often born as dwarfs or just will not grow to normal length or proportions.

Unlike normal mosaic axolotls, all documented NAGs so far have been reproductively sterile.

Citations

Strohl, L. Axolotl - Genetics - General Audience. https://docs.google.com/document/d/1kjdtH5JjnsXTe-IvbrT4kRnwCQTeHXTwmcSyUZtV4d4/edit

Strohl, L. Axolotl - Genetic Variations of Axolotls. https://docs.google.com/document/d/114QWTco6AVoQd_66kuGrRn1NtGl-EckrHQTRZ6v_9bw/edit#heading=h.vsuaxzlcggi

Strohl, L. Axolotl - What is Mosaicism? https://docs.google.com/document/d/1KD5O6gIsSm58fz8QxY4KLeHXXF8y0Oxg-qRnnwR_DNE/edit?pli=1