ClassX Video Lessons Axolotls: The salamanders that snack on each other (but don’t die) – Luis Zambrano
In 1864, a French zoologist named August Duméril became fascinated by a unique creature called the axolotl. Unlike most amphibians, which transform into land-dwelling adults, axolotls stay in their juvenile form and live in water their entire lives. Duméril tried to make them change by removing their gills, but they just grew them back! This amazing ability to regenerate isn’t just limited to gills; axolotls can regrow limbs, parts of their eyes, and even sections of their brains.
Axolotls are native to the wetlands of Mexico City and were considered sacred by the ancient Aztecs, who named them after a god called Xolotl. These creatures reach adulthood while still looking like tadpoles, with gills and a fin. Scientists think this permanent juvenile state, known as “neoteny,” evolved because their habitat was stable and safe, with few predators. In places where water dries up, other salamanders must adapt to life on land, but axolotls didn’t need to.
Interestingly, axolotls can still undergo metamorphosis if exposed to certain chemicals, but this often shortens their lifespan and reduces their ability to regenerate. Their regenerative powers are crucial because young axolotls compete for food and sometimes nibble on each other. Luckily, they can quickly regrow lost body parts. When an axolotl loses a limb, nearby tissues trigger growth. Skin cells cover the wound, and special cells form a mass that eventually becomes a new limb, thanks to proteins secreted by nerves.
Despite their rapid cell growth, axolotls rarely develop cancer. They have a system that controls cell division very effectively. Scientists have sequenced the axolotl’s genome, which is over ten times longer than the human genome. This is because salamanders lose DNA less frequently than other animals. Researchers found many repeated sequences in their DNA that don’t seem to have a function, but they also discovered genes important for regeneration. The secret might not be in unique genes but in how axolotls use their existing ones.
Even though axolotls are popular in scientific research, their numbers in the wild have dropped significantly. Hundreds of years ago, they thrived in the lakes around the Aztec capital. The Aztecs built chinampas, or floating gardens, which created perfect conditions for axolotls. However, after the Spanish arrived, the lakes were drained, and more water has been diverted since then. Now, wild axolotls are only found in Lake Xochimilco, where they face pollution and invasive species.
Efforts are being made to restore the ecosystem and revive the ancient chinampa farming method. If more people get involved, farmers could bring back abandoned chinampas, helping both the community and the axolotls. Protecting these salamanders might have benefits beyond their habitat. Scientists hope that one day we can use the axolotl’s cancer resistance and regenerative abilities in human medicine. Perhaps this incredible creature holds the key to breakthroughs in health and healing.
Using clay or modeling materials, create a model of an axolotl. Then, simulate the regeneration process by removing a limb and demonstrating how it would regrow. This hands-on activity will help you understand the biological processes involved in axolotl regeneration.
Conduct research on the concept of neoteny and how it applies to axolotls. Prepare a short presentation explaining why axolotls retain their juvenile features and how this adaptation benefits them in their natural habitat.
Participate in a class debate on the advantages and disadvantages of metamorphosis versus neoteny in amphibians. Consider the environmental factors and survival strategies that influence these developmental paths.
Investigate current conservation efforts aimed at protecting axolotls in the wild. Create a poster or digital presentation that outlines these efforts and suggests additional ways to support axolotl populations in their natural habitat.
Learn about genome sequencing and its role in understanding axolotl cancer resistance. Write a brief report on how studying the axolotl genome could lead to advancements in human medicine, particularly in cancer research.
In 1864, French zoologist August Duméril was intrigued while investigating the axolotl. Unlike many other amphibians that transform into terrestrial adults, axolotls retain their juvenile characteristics and remain aquatic throughout their lives. In an attempt to induce metamorphosis, Duméril spent months removing their gills, but in most cases, the axolotls simply grew them back. Indeed, axolotls are remarkable at regeneration; they can regenerate body parts ranging from amputated limbs to parts of their eyes and brains.
So how do they achieve this? This extraordinary salamander is native to the wetlands of Mexico City. The ancient Aztec people considered it the embodiment of a god named Xolotl, which is reflected in the axolotl’s name, roughly meaning “water monster.” Axolotls reach sexual maturity while still possessing gills and a tadpole-like dorsal fin. Scientists believe their perpetual juvenile state, known as “neoteny,” evolved due to their stable habitat. For salamanders that develop in environments that dry up, transitioning to land is crucial. However, the lakes where axolotls evolved remained stable year-round and had few aquatic predators, making it advantageous for them to forgo metamorphosis.
Interestingly, axolotls haven’t completely lost the ability to metamorphose. If exposed to certain substances, they can transition into adults, but this often results in shorter lifespans and a loss of some regenerative abilities. These regenerative capabilities may seem extraordinary, but axolotls have practical uses for them. As juveniles, they compete for resources, sometimes preying on each other. Fortunately, they can regenerate lost body parts quickly. When an axolotl loses a limb, the surrounding tissues stimulate growth in the area. Skin cells divide to cover the wound, and progenitor cells, which can develop into various tissues, form a mass at the injury site. Nearby nerves secrete growth-promoting proteins, leading to the emergence of a new limb over the following weeks.
This regenerative process could potentially lead to uncontrolled growth, but axolotls are remarkably resistant to cancer. They possess a system that tightly regulates cellular proliferation. To better understand the axolotl’s unique biology, scientists sequenced its genome, discovering it to be more than ten times longer than that of humans. Salamanders have more DNA than other vertebrates because they lose parts of it less frequently. In their investigation, scientists found many repeated sequences in the axolotl’s genome, most of which do not code for proteins and have no known function. They also identified genes crucial for regeneration. However, the key factor that distinguishes axolotl regeneration may not be unique genes but rather how they regulate their existing genes.
Despite being one of the most studied animals in science, the axolotl’s population in the wild has drastically declined. Hundreds of years ago, axolotls thrived in the lakes surrounding the Aztec capital. The Aztecs built islands called chinampas for agriculture, creating a vast system of canals that provided the ideal environment for axolotls. However, with the arrival of Spanish invaders, the lakes were drained, and even more water has been diverted in recent years. Today, wild axolotls are found only in Lake Xochimilco, where they face threats from pollution and invasive species.
Efforts are underway to restore the ecosystem and strengthen the ancient chinampa farming tradition. If interest grows, farmers could revive abandoned chinampas, benefiting both the local community and the axolotl. Ultimately, the advantages of conserving this salamander may extend beyond its habitat. Scientists hope that one day we can apply the axolotl’s remarkable tumor suppression and regenerative abilities to human medicine. Perhaps the secrets of this unique creature hold the key to significant advancements in health and healing.
Axolotl – A type of salamander native to Mexico, known for its ability to regenerate lost body parts and its retention of juvenile features throughout its life. – The axolotl is often studied in biology classes because of its remarkable ability to regenerate limbs.
Regeneration – The biological process by which organisms replace or restore lost or damaged tissues, organs, or limbs. – Scientists are researching how the regeneration abilities of certain animals, like the axolotl, could be applied to human medicine.
Neoteny – The retention of juvenile features in the adult stage of an organism, often seen in certain amphibians like the axolotl. – Neoteny in axolotls allows them to retain their larval gills even as adults, which is unusual for amphibians.
Habitat – The natural environment in which a particular species lives and grows. – The destruction of the axolotl’s natural habitat in Mexico has led to a decline in their population.
Pollution – The introduction of harmful substances or products into the environment, which can negatively impact ecosystems and organisms. – Water pollution in Mexico City has severely affected the axolotl’s habitat, threatening its survival.
Conservation – The protection and preservation of natural resources and environments to prevent their degradation or destruction. – Conservation efforts are crucial to protect the axolotl from extinction due to habitat loss and pollution.
Ecosystem – A biological community of interacting organisms and their physical environment. – The axolotl plays a vital role in its ecosystem by controlling insect populations and serving as prey for larger animals.
Cancer – A disease characterized by the uncontrolled division of abnormal cells in a part of the body. – Researchers are studying the axolotl’s regenerative abilities to gain insights into potential cancer treatments.
Amphibians – A class of cold-blooded vertebrates that includes frogs, toads, newts, and salamanders, which typically have a life cycle that includes both aquatic and terrestrial stages. – Amphibians like the axolotl are important indicators of environmental health due to their sensitivity to pollution.
Mexico – A country in North America, known for its rich biodiversity and as the native habitat of the axolotl. – Mexico is home to unique species like the axolotl, which are found in the lakes and canals of the Valley of Mexico.
