Who Are These Axolotls?

“Fish with legs?”. There is a controversy that these axolotls are a type of fish species, but in reality, they are a type of salamander. Axolotls binomially known as Ambystoma mexicanum, and commonly known as Mexican salamander. One of the main reasons for these axolotls to become a talk of science is the display of paedomorphism, which means the retention of juvenile characteristics in sexually mature individuals. These salamanders have morphological characteristics such as the development of external gills and ability to regenerate lost limbs and even other body organs. Even though this regrowth is an advantageous ability, they are endangered by various anthropogenic activities including pollution and habitat loss, as well as threatened by the interaction with invasive species inhibiting their natural habitat.  

Classification of the Axolotls

Axolotls are salamanders, so like all salamanders they belong to the group of vertebrates called the Amphibians. Scientifically, it is called the class Amphibia. In this class they are further classified into the order Caudata. This order is further broken down into the family Ambystomatidae which is composed of mole salamanders. As above-mentioned the binomial name is Ambystoma mexicanum, as per the species names it reflects its native location, Mexico. They are found mainly in freshwater lakes and canals of Mexico, particularly in Lake Xochimilco. 

Natural Habitat and Related Threats 

Naturally, axolotls are distributed in Lake Xochimilco and Lake Chalco in Mexico. But however, with Lake Chalco now drained due to factors such as urbanization, these axolotls are now primarily confined to the remnants of the Lake Xochimilco comprising a network of canals. These high-altitude lakes provide ideal environmental conditions for axolotls due to their cooler temperature conditions, abundant vegetation and an aquatic ecosystem which support their rather unique lifecycle. 

According to the IUCN red list status, axolotls are categorized as Critically Endangered (CR) species. This is due to threats incurred by urbanization, Mexico city’s continuous expansion has led to severe habitat loss; pollution, the release of industrial waste, and contamination with untreated sewage have drastically reduced the water quality of Lake Xochimilco; and lastly the introduction of non-native fish like tilapia and carp has further endangered the axolotls since they are considered invasive since they compete with these individuals for food and also prey on axolotls’ juveniles. 

Efforts have been directed to restore parts of the Xochimilco ecosystem through the creation and integrations of floating islands made from natural materials called chinampas as a measure to conserve these axolotls and other native species. However, with these threats their extended survival in the wild remains uncertain. 

Life Cycle and Reproduction of Axolotls

Axolotls have derived a mode of development characterized by metamorphic failure which is termed paedomorphism. This is one of the most fascinating aspects. This neoteny, meaning they are able to retain larval/juvenile traits into their latter stages of adulthood, is a distinct characteristic of the axolotls. Because, unlike other salamanders that under metamorphosis, these salamanders remain in their larval stage, complete with external gills and a dorsal fin, the specialty is that they can yet reach sexual maturity and reproduce.   

Life Cycle of an Axolotl

The life cycle of an axolotl is composed of 3 main stages: 

1. Egg Stage – This is initially when female axolotls lay their eggs, after mating, on the surface of aquatic plants or rocks. According to records, each female can lay up to a maximum of 1000 eggs, though 300-600 eggs are on average the most common. Once laid, the eggs typically take about 2 weeks to hatch.

1. Larval Stage – After hatching the axolotls are now in their larval stage and completely aquatic. They rely on their external gills for breathing and respiration and at this stage they begin to feed on small invertebrates such as brine shrimp.

1. Paedomorphic Adult - Other salamander species undergo full metamorphosis, but these axolotls remain in their larval form even after reaching sexual maturity,which is typically at around 12-18 months. There are records that in rare instances, axolotls may metamorphose into a terrestrial form, though this requires specific environmental triggers, such as the use of hormones or drastic changes in water conditions.

When it comes to their lifespan; in captivity, axolotls can live for up to 15 years under ideal conditions and proper care. In their natural habitat, however, their lifespan is much shorter due to predation, anthropogenic threats, and food scarcity. Therefore, in the wild, they live up to 5-6 years. 

Diet and their Feeding Habits

Axolotls are carnivorous, therefore, they feed on a variety of small aquatic organisms. Their diet consists mainly of small fish, and small invertebrates such as mollusks, crustaceans, aquatic insects, and worms.

Whereas in captivity, taking benefits from their opportunistic feeding habits Axolotls are given a diet that includes high protein such as bloodworms, brine shrimp, earthworms, pellets which are formulated for carnivorous fish or amphibians. You can visit Melbourne Tropical Fish to purchase the required food, it is available in a wide range of varieties and affordable prices.

One concerning behavior observed in young axolotls is cannibalism, particularly at instances when food is scarce. Newly hatched axolotls may tend to nibble on their siblings' limbs. Fortunately, axolotls can regenerate their limbs and skin, so these injuries aren’t a threat to their lives.

Axolotls in Pet Trade 

It is funny why most aquarium keepers are interested in keeping axolotls, it is for their rather “cute” appearance. Apart from their appearance, due to their hardy nature, and easy-to-care ability, axolotls have become popular among aquarists. However, proper care is essential to ensure their well-being. If you are considering buying axolotls for your aquarium, Melbourne Tropical Fish is the ideal place for your purchase. Melbourne Tropical Fish has a collection of well-seasoned axolotls for sale. 

Axolotls Care

Ideal Aquarium Size for Axolotls

Axolotls on average grow up to a length of 10 inches (25 cm), therefore, they require a spacious tank. An individual axolotl should be kept in a tank that could at least hold up to 75 litres  For a pair or more axolotl, a tank of 150 litres or larger is recommended. 

Aquarium essentials

Water Temperature – Axolotls prefer rather cool waters. The most adequate temperature range advisable is 16°C - 18°C. 

Filtration system- It is crucial for the water to be kept clean and well-oxygenated. However, the filter should not create strong currents. These creatures prefer slow-moving waters. 

Substrate- A fine sand substrate to prevent impaction at the bottom layer. 

Hideouts- Axolotls are naturally shy and need places to hide. Adding caves, rocks, and aquatic plants is ideal for axolotl tank aqua-scaping.

Breeding Axolotls in Captivity

Axolotls are relatively easy to breed in captivity. They reach sexual maturity at around 12-18 months and typically breed during the winter season. In their mating behavior, a male performs a courtship dance, waving his tail and depositing sperm packets called spermatophores on the tank bottom surface. The female then picks up these spermatophores with her cloaca, which then fertilizes her eggs.

After fertilization, the female lays her eggs on aquatic plants or other surfaces. The eggs should be carefully removed to a separate tank to protect them from being eaten by adult axolotls. The eggs will hatch in about 2 weeks, and the larvae can be fed with brine shrimp or finely chopped bloodworms.

Threats in the Wild

In their natural habitat, they fall prey to waders and other aquatic birds such as herons. Apart from predation, axolotls are threatened by the competition for food incurred by non-native species like tilapia and carp. Axolotl larvae are also preyed on by these invasive fauna. 

Anthropogenic activities such as Habitat degradation, pollution, and the introduction of invasive species have dramatically reduced the population of axolotls in the wild. According to the IUCN listing, axolotls have been classified as Critically Endangered (CR) since 2006. 

Facilitating the conservation of these endangered fauna is of utmost importance.