Axolotl (amphibians)
The axolotl, also known as Ambystoma mexicanum, is a unique amphibian native to Mexico, often referred to as the Mexican walking fish. This intriguing creature is a type of salamander that has gained popularity as a pet and in laboratory settings, primarily due to its remarkable regenerative abilities, allowing it to regrow limbs and even organs. Axolotls inhabit aquatic environments, characterized by their striking feather-like gills and webbed feet, and they can grow between 6 to 18 inches in length. Unfortunately, they are critically endangered in the wild, primarily found in the Xochimilco Ecological Park, where invasive species and pollution threaten their survival.
Historically, axolotls were abundant in their native habitat near Lake Texcoco, but population declines began with urban development and environmental changes. They have become a subject of scientific research due to their regenerative capabilities, with ongoing studies aimed at understanding the underlying mechanisms that could inform medical advancements for humans. While their popularity in culture and as pets may raise awareness about their plight, effective conservation efforts rely on collaboration between local communities and scientific experts to restore their habitats and mitigate the threats they face in the wild.
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Axolotl (amphibians)
The axolotl, or Ambystoma mexicanum, is a native amphibian of Mexico also known as the Mexican walking fish. The axolotl has lived in Mexico for hundreds of years, though it is now critically endangered in the wild. The axolotl, a type of salamander, has become a popular pet and laboratory research animal in part because of its unique features, including its ability to regenerate limbs and even organs. Thousands of axolotls are bred and bought as pets and lab animals, in part because they are hardy and reproduce easily. These animals have unique physical features, including feather-like gills surrounding their head, which make them easy to identify.
Background
Axolotls live for ten to fifteen years and may grow to be between 6 and 18 inches long. In the wild, they are carnivorous, or meat-eating, predators that eat worms, insect larvae, crustaceans, and some types of fish.
Wild axolotls have dark coloring, including gray and black along with dark green and brown patterns. Their feather-liked gills can be gray, brown, or purple. Many captive axolotls have been bred to be lighter in color, appearing white to light pink with pink or red gills. These light-colored axolotls would not survive in the wild because they would be easily spotted by predators.
Axolotls evolved recently compared to other species of salamanders. In the past, they lived near Lake Texcoco in central Mexico, where they were commonly eaten by Indigenous peoples.
When Europeans colonized North America, beginning in the 1500s, they began settlement near the axolotls’ habitat, which displaced the creatures and began to reduce their population. The draining of Lake Texcoco and subsequent development of Mexico City further encroached on the axolotls’ habitat. In the 1800s, though, the wild population was still robust, and European scientists noticed the animals’ unique ability to regenerate. They collected specimens to be used in scientific studies, the descendants of which are still used in laboratory testing. Today, axolotls are considered critically endangered in the wild and live in canals in the protected Xochimilco Ecological Park in Mexico.
Overview
Axolotls live only in water. However, because they have legs, scientists believe that they evolved from animals that walked on land. Axolotls maintain juvenile traits throughout their lives and even into adulthood. Like all amphibians, axolotls are born in water; however, unlike other amphibians, axolotls do not leave the water in adulthood. Axolotls have feather-like gills that stick out around their heads. They use these gills to obtain oxygen. Axolotls also keep their dorsal fins, which run down their back, and webbed feet.
Between the 1990s and 2010s, scientists noted a steep decline in the animal’s wild population. In 1998, scientists conducted the first well-documented study of the number of axolotls in Xochimilco. Researchers found roughly six thousand axolotls per square kilometer. Only a few years later, in 2000, they found only one thousand animals per square kilometer. By 2008, this number had dwindled to one hundred animals per square kilometer. Around the same time, axolotls were classified as critically endangered. In 2015, scientists believed that axolotls had gone extinct in the wild, but they have since found the animals in their native range, though they are rare.
Scientists who study wild axolotls want to implement programs to help save them. However, these scientists believe that reintroducing new axolotls into the wild will not improve the overall population until people remedy the problems that have caused their rapid decline.
Wild axolotls face two major hurdles to survival. The first is invasive fish in the canals where axolotls live. People have introduced these fish, including invasive carp, to give the people there an additional source of protein; however, these invasive fish have overtaken the waterways and killed off many native species. The second problem that axolotls face is pollution. Lake Xochimilco is eutrophic, which means it contains nutrients from agricultural runoff that can cause plants and algae to bloom, deplete oxygen, and kill other species. Scientists hope to decrease the number of invasive fish and pollution in Lake Xochimilco to give the axolotls a chance at survival.
Although axolotls are nearly extinct in the wild, they are common in homes and laboratories throughout the world. Axolotls are popular aquatic pets and also attractions at aquariums. However, many of the animals in captivity are severely inbred, making them more susceptible to disease. Having inbred axolotls in laboratories also means that scientists have a narrow view of the species, since they are not studying animals with diverse genetics. Nevertheless, axolotls are often studied in laboratories, in large part because of their ability to regenerate lost limbs and organs. The regeneration of an entire limb takes only forty days for some axolotls. Scientists have found that certain pieces of microRNA make it possible for the animals to regenerate. Other animals, such as starfish, can also regenerate limbs and organs. However, axolotl regeneration is unique because the regenerated limbs and organs are as well-formed as the originals. Scientists hope to eventually make medical breakthroughs for humans by studying the interesting features of the axolotl.
There is hope that the increasing popularity of axolotls in popular culture may help spread awareness of their struggles in the wild. Axolotls continue to be popular, appearing as characters in animated films, inspiring a Pokémon character, and appearing in the video game Minecraft in 2021. Scientists hope this increase in popularity will bring attention to their plight. However, scientists state that true progress in increasing the wild population of axolotls will come when the local knowledge of farmers can combine with the scientific knowledge of experts who study the animal and form a plan to clean up the lake habitats of the axolotls.
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