The axolotl is an animal of the Urodela family. It is therefore not a fish, but an amphibian, and more precisely a salamander. Of its real name Ambystoma mexicanum, it is native to Mexico, where it lived in cold water lakes that are now extinct. At present, it unfortunately appears on the CITES list of endangered species. It is therefore rarely found in the wild. On the other hand, axolotls are raised in many farms, as it is widely used as a laboratory animal.
The axolotl has the amazing ability to regenerate its organs identically if they are damaged, which is of great interest to aquarium researchers. But this is not the only particularity of the axolotl. It is also capable of remaining in the larval stage throughout its life, which does not prevent it from reaching sexual maturity and reproducing. This phenomenon is called “neotenia”. This is thought to be related to a lower activity of the thyroid gland, probably due to their very low iodine environment. Axolotls rarely metamorphose spontaneously into adults. In captivity, transformation can be achieved by hormonal treatment with thyroid hormones (thyroxine).
Who is the axolotl?
The neotenic axolotl has a round head and a wide mouth, which give it that sympathetic look that is so appealing. On each side float its gills, which, unlike those of fish, are external. By coloring themselves more or less vividly, they can give information about the axolotl’s state of excitement. Its elongated body is equipped with 4 legs that allow it to move at the bottom of the water.
Axolotls can be of a wide variety of colors, white (also called “leukistic”), black or gold. They are mottled brown in the wild. The axolotls on sale in pet stores are most often albino (this color hardly exists in the wild). Even if they remain in the larval stage, they can still reach 30 centimeters, which must be taken into consideration before acquiring them.
Axolotls are active at night and at dusk. They have an exclusively carnivorous diet.
If they remain in the larval stage, they can easily live for about fifteen years. Some specimens reach the advanced age of twenty years! On the other hand, if they metamorphose into adults, their life expectancy is much shorter (about 5 years).
The axolotl is a carnivore. It has small teeth, which are generally not very effective for cutting and pulling. You therefore have no reason to fear its bite!
Its diet should be low in fat, and rich in proteins and vitamins. In the wild it feeds on insects and small freshwater fish. In captivity, it can be fed with live food or not. Food specially designed for axolotls exists, but is still difficult to find in pet shops. You can first give it small invertebrates (mud worms), daphnia or artemia nauplias. However, in adulthood it is likely that this will not be enough to cover its energy needs.
Some pellets for carnivorous fish may be suitable. It is also possible to give them small pieces of freshwater fish (e.g. trout), or earthworms. Once adult, the axolotl does not need to eat every day. It is important to find the right frequency so that all its food is swallowed and does not pollute the bottom of the aquarium.
As a precaution, it is advisable to restrict the intake of iodine (present in food of marine origin) as much as possible because of its potentially stimulating effect on the functioning of the thyroid gland.
Can my axolotl metamorphose?
Spontaneous metamorphosis is quite rare. In theory, the axolotl lacks the thyroid hormones that allow it to undergo this transformation. It is rather inadvisable for amateurs to try to provoke it, because it is a rather delicate step that leads to profound changes in the axolotl’s morphology. Moreover, if he survives it, it will greatly reduce his life expectancy.
Carried out under poor conditions, the metamorphosis may be fatal or incomplete, and may result in a half-adult-half larval axolotl with hybrid characteristics. Some axolotls, especially those that come from cross-breeding with other salamander species, could metamorphose if the water level decreases, and if they have the possibility to come out of the water at will, for example by being placed in a semi-aquatic terrarium. However, most are unable to do so and this manoeuvre can therefore be rather dangerous. In most cases, thyroid hormones are still necessary. Once transformed, the axolotl acquires a morphology very close to that of the Tiger Salamander, with which it has long been confused. It then adopts a terrestrial lifestyle.