What Color Are Wild Axolotls? Wild Type vs Pink Axolotls

What does a wild axolotl look like?

A wild axolotl is far less eye-catching than its famous pink cousins. Its body and tail are a dark mottled olive, brown or charcoal gray, often paler on the belly. Black spots are scattered over the skin, and small gold or metallic flecks catch the light. The eyes are dark with a golden ring, and the gills are dark red to purplish.

This coloring is perfect camouflage in the murky water of Xochimilco, where axolotls rest among water plants, roots and mud. It helps them hide from herons and egrets above and from large fish below, and lets them ambush their own prey.

Wild axolotls can also adjust their shade a little. By spreading or concentrating the pigment in certain skin cells, they become slightly lighter or darker to match their background.

How do axolotl colors work?

An axolotl’s color comes from three kinds of pigment cells in the skin:

• Melanophores contain melanin, a black or brown pigment. They give wild axolotls their dark base color.
• Xanthophores contain yellow pigments.
• Iridophores contain tiny reflective crystals that create shiny, metallic gold spots.

A wild-type axolotl has all three working together. Each captive color form is the result of a change (mutation) in one or more of the genes that build or control these cells. Breeders have combined these genes to produce many different looks.

What are the main axolotl color forms?

Animals with two or more of these mutations combine their effects. For example, an axolotl that is both leucistic and albino is white with pink eyes.

Why are leucistic axolotls pink?

Leucism is different from albinism. A leucistic axolotl can still make melanin, which is why its eyes stay dark and it may have a few dark freckles. The problem is that, during development, most of its pigment cells never travel to the skin.

Without those cells the skin is pale and somewhat transparent. The red blood in the vessels underneath shows through, giving the animal its pink tone, and the feathery gills look bright red. Scientists have linked the leucistic form to a mutation in a gene that guides pigment cells as they move through the embryo.

Where did pink axolotls come from?

Almost all captive axolotls descend from a few dozen animals shipped from Mexico to Paris in 1863–1864. Pale, leucistic animals appeared in captive colonies, and they were kept and bred because they were easier to study: their pale skin and see-through embryos make it simpler to watch cells and tissues develop.

The albino gene came later. In the 1960s, researchers crossed axolotls with albino tiger salamanders, their close relatives, and bred the albino trait into axolotl lines. This is one reason scientists treat captive axolotls as genetically different from the wild population.

Laboratories have also created axolotls with a jellyfish gene that makes them glow green under blue or ultraviolet light. These animals are used to track cells, for example while studying how axolotls regenerate.

How do scientists use axolotl colors?

Color forms are useful tools in research. Pale leucistic and albino embryos are almost transparent, so scientists can watch organs, nerves and blood vessels form under a microscope without harming the animal. Pigment genes were also among the first axolotl genes to be studied, helping scientists understand how inherited traits pass from parents to offspring.

Researchers can also transplant a small piece of dark wild-type tissue onto a pale animal. Because the dark cells stand out clearly, they can follow where the transplanted cells move and what they become. Experiments like this helped show how pigment cells migrate from the developing spinal cord to the skin, a process that works in a similar way in other vertebrates, including humans.

Why are wild axolotls never pink?

Pale axolotls would be easy targets for herons and fish in open water, so in the wild they would be unlikely to survive long. The genes for pale colors are also rare in nature, and the wild population is now so small that such animals are essentially unknown.

That contrast is a useful reminder: the many pink axolotls in pet shops do not reflect the true state of the species. In the wild, dark axolotls are struggling to survive in polluted canals, as explained in are axolotls endangered?.