Axolotl

The axolotl (/ˈæksəlɒtəl/; from Classical Nahuatl: āxōlōtl; Ambystoma mexicanum) is a species of mole salamander. Unlike most salamanders, axolotls are neotenic, meaning they fully maturing without undergoing metamorphosis. As a result, they remain fully aquatic with obvious external gills throughout their lives, which makes them look similar to the larval stage of other salamanders.

Axolotls originally lived in a system of interconnected wetlands and lakes in the highlands of Mexico, particularly in smaller lakes like Xochimilco and Chalco. Unfortunately, human activities, including the draining of these lakes starting with the Aztecs and continuing into the 20th century, have destroyed much of their natural habitat. Today, wild axolotls are near extinction due to habitat loss and invasive species like tilapia and carp. They are listed as critically endangered by the International Union for Conservation of Nature.

Despite their decline in the wild, axolotls are widely studied in scientific research because of their amazing ability to regenerate lost body parts, such as limbs, gills, and even parts of their eyes and brains. This makes them valuable model organisms. Axolotls are also popular in zoos and public aquariums, and some people keep them as pets. They have also inspired many characters and stories in contemporary culture.

Nomenclature

The word "axolotl" comes from the Nahuatl language and can mean many things like "water slave", "water servant", or "water sprite". It is named after Xolotl, an Aztec God who ruled over fire, lightning, the dead, and twins, among other things.

Sometimes people use the term "Mexican axolotl" to make it clear they are talking about this specific species, since the word "axolotl" can also refer to other similar salamanders that do not change into adults.

Description

Axolotls are special types of salamanders that stay in water their whole lives. They usually grow between 15 to 45 cm long, with 23 cm being common. They look like they are still babies because they keep their external gills, unlike most salamanders that lose them when they grow up. This trait is called neoteny.

Axolotls have wide heads and eyes without lids. Their limbs are small with long, thin digits. They have three pairs of external gill stalks behind their heads, which help them breathe. Males can be identified by swollen areas near their tails, while females look wider when they have eggs. Axolotls come in many colors, including brown, pink, grey, white, and black, depending on genetic changes. Scientists have also studied their DNA, finding it very large but encoding a similar number of proteins as humans. One amazing ability of axolotls is their power to regrow lost body parts, such as limbs, tails, and even parts of their brains and eyes. They can also adapt to living on land if given certain hormones, though they usually stay in water.

Wild population

Lake Xochimilco is one of the last refuges of the wild axolotl. Axolotls belong to the same group as the tiger salamander, sharing a common ancestry with other Mexican salamanders. They live in high-altitude water bodies surrounded by risky land environments, which may have helped them develop neoteny—the ability to stay aquatic throughout their lives.

Axolotls are carnivores, eating small animals like mollusks, worms, insects, and small fish. They find food using their sense of smell and can quickly grab it with strong suction. Wild axolotls reach sexual maturity at about 1.5 years old. However, their natural habitat in the Mexican Central Valley has greatly shrunk due to the growth of Mexico City. Pollution, invasive fish, and loss of genetic diversity all threaten their survival. Conservation efforts include breeding axolotls in labs and releasing them into cleaner water, though challenges remain.

Relation to humans

The axolotl has a long history with humans. Explorer Alexander von Humboldt wrote about people in Mexico eating axolotls. In 1863, scientists in Paris received axolotls from Mexico and began studying them. These studies helped scientists learn about how some animals stay young forever.

Today, axolotls are important in scientific research. They are easy to care for in labs and have special features that help scientists study heart development, nerve growth, and how animals can regrow lost body parts. Their embryos are large and easy to see, making them perfect for studying how animals develop. Recent studies have also explored how to use harmless viruses to study genes in axolotl brains.

Axolotls are also popular pets. They need cool water around 16–18 °C (61–64 °F) to stay healthy. Pet axolotls eat food like trout pellets, bloodworms, earthworms, and waxworms. It’s important to give them safe bedding to avoid health problems. In Mexico, axolotls are culturally important, appearing in art, money, and even video games like Minecraft. They also inspired characters like Toothless in How to Train Your Dragon.