The Axolotl (Ambystoma mexicanum) is a unique amphibian that can be found in Mexico. It is often called the “Mexican Walking Fish” and is a very unique and fascinating species.
The Axolotl is a member of the salamander family and is closely related to the tiger salamander. It has several unique features that make it distinct from other amphibians. For instance, unlike other salamanders, axolotls generally do not go through a final stage of metamorphosis, becoming fully formed while still larvae!
It is one of the national animals of Mexico and only exists in a few select locations in the wild.
Physical Description
The axolotl is a permanently aquatic salamander that has an eel-like body. It can grow up to 9 inches in length, and its coloration can vary from light pinkish brown to olive green. There are many colors of axolotl that have been developed through genetic manipulation and in the lab, but do not occur in the wild.
The axolotl has external gills and large, lidless eyes. Its most distinctive feature is its ability to regenerate lost body parts. These characteristics make the Axolotl an ideal subject for scientific research.
The axolotl has webbed feet like most aquatic animals, and has also developed lungs which allow it to breathe oxygen at the surface of the water.
Axolotls maintain their gills and dorsal fins as they age, never going through the metamorphological transformation into mature salamanders. As they don’t go through this final metamorphose, they are technically not truly a salamander. However metamorphosis can be forced in this animal if they are exposed to sufficient amounts of iodine.
When this happens, they transform into a type of mole salamander, and their behaviour changes, developing a fondness of digging and burrowing.
Location & Habitat
There is only one place on Earth where axolotls breed outside of captivity, and that is in Mexico. More specifically Lake Xochimilco, and the surrounding canals and waterways in the south of Mexico City.
They can now be found however, in zoos and aquariums around the world. In fact, there are more axolotls in captivity today than there are in the wild. They used to have a much greater range in Mexico, but habitat loss due to human activity reduced their wild range.
They face many environmental pressures, particularly the threat of pollution on their fragile lake due to the threat of overcrowding and poverty with their surrounding human population.
Diet
The axolotl is a carnivore through and through. In the wild their range is limited, and so therefore so is the food that they have available to them. They will happily eat small fish, brine shrimp, worms, snails, insects and other baby amphibians in their tadpole stage. As they grow up, they may even eat other types of salamander, if they are able to fit them in their mouth.
It uses its long tongue to capture prey. Once the prey is captured, the axolotl will crush it with its powerful jaws.
In captivity, they are often fed other insects such as crickets, slugs, woodlice, California blackworms and pellets, like salmon pellets formulated to give them balanced and nutritious diet.
Reproduction
Axolotls reproduce by external fertilization. The breeding process starts when males release sperm in the water and females release eggs. The sperm then combines with the eggs, resulting in fertilized eggs. The female can lay up to 1000 eggs!
Baby axolotls go through five stages during their lifecycle: two embryonic stages, the larval stage before they develop limbs, the juvenile stage where limbs develop, and the adult stage.
When the fertilized eggs hatch after their embryonic stages of development, they become tiny tadpoles known as larvae. The young larval stage is the most important phase of a baby axolotl’s life because this is when they learn to swim and feed. These larvae can then develop into adults within 6-18 months, but in most cases will never metamorphose beyond their larval form into full salamanders.
In the wild, axolotls typically live for about 10-15 years. However, in captivity, they can live for up to 20 years.
Axolotls In Science And Research
Axolotls have been and continue to be studied widely by scientists. They have been subject to many genetic manipulations and studies by researchers looking to understand how these animals are able to regenerate limbs. To understand and explore this could lead to incredible breakthroughs in medicine.
Some have also been genetically modified to contain the green fluorescent protein originally found in some jellyfish. This causes them to fluoresce under UV light, in which researchers can study the growth and change of specific cells, including cancer cells. They are a scientifically important species and need to be protected both in the wild, captive habitats and in the lab.
Predators And Threats
Axolotls have plenty to worry about in the wild. They were once at the top of the food chain in their habitat, only having to watch out for the occasional bird of prey, such as storks or herons who were their main predators. But with the introduction of a non native species of carp and tilapia from Asia and Africa, the axolotl has to be wary of predation from these species now too.
In captivity and in the wild, baby axolotls have to watch out for predation from adult axolotls too. That includes mothers when food availability is scarce. These animals can and do resort to cannibalism, particularly of unhatched eggs. This is a big problem, and even in captive populations where food is managed, it is still a problem.
In captivity, adults are usually removed from an enclosure where a clutch has been laid to improve the mortality rate for that clutch. This is critical to ensure survival.
The biggest threat to wild axolotl however, comes from humans. Particularly the environmental impact of overcrowding, over consumption and pollution of their fragile lake habitat.
Conservation Status
It is a sad fact, that the axolotl is on the brink of extinction in the wild. A species that at one point had abundant numbers, and a habitat across many lakes in Mexico, has been catastrophically to the brink. Most of the damage to these creatures was done in pre-industrial times, when the Spanish defeated the Aztec Empire and drained many of the lakes where the axolotl lived. They destroyed their habitat.
Now, axolotls are considered critically endangered on the IUCN Red List, and as of 2020, it was believed that as few as 50 to 1000 individuals are left in the wild. They are also listed under Appendix II of the CITES Index which limits trade of this endangered species.
Modern environmental pressures, as mentioned above, particularly water pollution and the pressures of a city bursting at its sides are devastating the axolotls remaining and limited habitat. The introduction of invasive and competing fish from Asia and Africa, specifically talapia and perch is also a major factor in the devastation to the species. For an animal that is revered as a national symbol, humans sure are stacking the odds against them.
Fortunately, they are a popular species in captivity and it is estimated that there may be as many as 1 million in the tanks of various labs, homes, zoos and aquatic centres around the world.
