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AXOLOTL

The Mexican axolotl has the largest genome ever sequenced, 10 times larger than the human genome. Photo: Research Institute of Molecular Pathology (IMP)

If there is a creature that, due to its biological characteristics, has attracted the interest of scientists, it is the salamander, since it is the only vertebrate animal capable of regeneration.

In the group of these amphibians, the Mexican axolotl -or Axolotl- (Ambystoma mexicanum) stands out for its extraordinary processes to regenerate amputated limbs and other organs and tissues of the body.

It has been observed, for example, that if these animals lose a limb, they are able to regenerate it in a matter of weeks, with all their bones, muscles and nerves in the appropriate places.

Even more fascinating, the researchers say, is the axolotl's ability to repair its spinal cord when it is injured and make it function as if it had not been damaged.

Not only that. This amphibian, which is in danger of extinction in its natural habitat, has also attracted the interest of researchers because of the relative ease with which it can reproduce.

For this reason, for about 150 years scientists have been cultivating these animals in the laboratory and trying to discover the secrets of their extraordinary biological processes and their potential applications in human medicine.

For example, in the repair of brain or spinal cord injuries and the prevention of heart scars.

Now an international team of scientists has discovered one of its secrets: the axolotl has the largest genome ever sequenced, much larger than the human.

This amphibian has 32 billion base pairs of DNA, 10 times larger than the human genome, which has 3.2 billion base pairs of DNA.

Dr. Elly Tanaka of the Vienna Molecular Pathology Research Institute has succeeded in cultivating one of the largest populations of axolotls in the laboratory.

Together with her team, she developed advanced molecular tools for the axolotl, which revealed the protein coding sequences in the animal's genome.

Thus, the scientists were able to identify the cells responsible for restarting the regeneration process and describe the molecular pathways that control these processes.

But to understand in detail how regeneration works and why regeneration is such a limited process in most species, researchers needed to have access to amphibian genomic data in order to study its evolution and gene regulation.

This had not been completed due to the enormous size of this genome - 32 billion base pairs of DNA, until now.

"We now have the (genetic) map in our hands to investigate how complicated structures such as limbs can regenerate," says study co-author Sergei Nowoshilow.

"This is a watershed moment for the community of scientists who work with the axolotl, a true milestone in a research adventure that began more than 150 years ago," he adds.

The entire genome of the axolotl, the largest ever decoded, was sequenced with the collaboration of researchers using new software systems developed specifically for the study.

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The Mexican axolotl (pronounced axolotl) is a salamander with the unusual characteristic of retaining its larval features in adulthood. This condition, which is known as neoteny, means that it retains its tadpole dorsal fin - which runs almost the entire length of its body - and its external gills, which protrude from the back of its broad feathery head.

The axolotl is found only in the Xochimilco lake complex (pronounced Sochimilco), near Mexico City, and differs from most other salamanders in that it lives permanently in the water. In extremely rare cases, the axolotl matures and comes out of the water, but in most cases they prefer to stay at the bottom of the lakes and canals of Xochimilco.

The axolotl, a close relative of the tiger salamander, can be quite large, reaching lengths of up to 30 centimeters, although its average size is 15 cm. The axolotl is usually black or mottled brown, although albino and white varieties are also relatively common, especially among captive-bred specimens.

The axolotl is long-lived, reaching up to 15 years of age, feeding on mollusks, worms, insect larvae, crustaceans and some fish. This species, accustomed to the role of predator in its habitat, has begun to suffer the introduction of large fish in its lake habitat. Natural threats include birds of prey such as herons.

Its population is in decline, as demand from nearby Mexico City has led to drainage and contamination of much of the waters of the Xochimilco lake complex. It is also very common to use in the aquarium trade and the roasted axolotl is considered a delicacy in Mexico, which has led to its number being further reduced. It is considered a very threatened species.