It is the Mexican axolotl ( Ambystoma mexicanum ) , a strange and curious amphibian that never grows, retains its tadpole appearance throughout its life and, if it loses a limb, it grows back quickly. Hence, he is considered "eternally young" and received the nickname "Peter Pan of the sea."
The fact that it does not undergo metamorphosis and does not mature is because its pituitary gland does not release a hormone that activates the thyroid glands. By administering thyroid hormones , specifically thyroxine, scientists have managed to mature, develop lungs and transform into an adult form that does not exist in nature.
