In Aztec mythology, the Fifth Sun was created by the gods. Still, it was not able to move across the sky without the nourishment of sacrifice. The god Xolotl changed himself into other forms to evade detection, but was banished to live forever in darkness.
Axolotls are a type of salamander found only in the area of Lake Xochimilco outside Mexico City. They are unique because they can regenerate almost any part of their body, including missing limbs, tails, organs, parts of the eye, and even parts of their brain.
Axolotls are members of the tiger salamander species complex, and are neotenic, meaning they keep their juvenile characteristics into adulthood.
When axolotls were first shipped from Mexico to prominent French zoologist Auguste Dumeril in the 1860s, he was certain that they were the larvae of an unknown type of salamander. But 6 months later, he discovered that they had reproduced.
Mexican lake salamanders are found in large, permanent bodies of water surrounded by desert, and historically did not have any large, predatory fish. The salamanders thrive in these lakes because they are the only suitable habitat in a harsh and dry terrestrial environment.
The transformation of the axolotl was first discovered in 1865 by French zoologist Dumeril, who fed thyroid tissue to his axolotls. The transformation took place when the axolotls shed their larval skin and ventured onto land.
All organisms have some level of regeneration abilities. Still, only invertebrates can regenerate their whole bodies, and the axolotl can regenerate its entire body, including its limbs.
An axolotl’s limb regrows by a process called de-differentiation, where regular bone, cartilage, or muscle cells lose their identity and transform back into stem cells. The stem cells start reforming bone, skin, and veins, and eventually the limb grows back completely.
The axolotl can regenerate parts of its brain and spinal cord after an injury, and can do this by de-differentiating stem cells. This ability may be locked within humans, and could help people suffering from organ failures or serious burns.
Researchers have found that macrophages, a type of cell we readily have, are an important component for axolotl regeneration. Transforming growth factor is also important in preventing scar tissue in injured human embryos during the first trimester.
Researchers believe that the regeneration abilities of mice digits are due to a type of stem cell that lies beneath the fingernail. These cells may also be a remnant from a time when our regeneration abilities were stronger.
The axolotl is a unique creature, and is teetering on the brink of extinction. Their population has exponentially declined in the last few decades.
The axolotl is found only in Lake Xochimilco, which is now a series of small canals. The ancient cities of this area looked a lot like the Venice of today. Still, they were eventually drained to allow urban expansion.
The axolotl is the most distributed amphibian in the world, but is almost gone from Lake Xochimilco. However, in labs around the world, the axolotl is abundant. Still, the colonies are becoming inbred, lacking the genetic diversity that wards off disease.
Some scientists have proposed reintroducing captive axolotls into Lake Xochimilco to save the species, but cleaning up the lake seems unlikely.
Scientists are reintroducing axolotls to a freshwater lake near Mexico’s National Autonomous University, where they are tracking the animals using radio transmitters. Eventually, the animals will breed, and a new type of a semi-wild population may be born.
Mexico is one of the most biodiverse countries in the world, with thousands of unique, endemic species. In addition, the grasslands of Mexico are teeming with biodiversity, with as many different types of grasses as there are different types of trees in a tropical rainforest.