The axolotl, with its permanent grin and youthful-looking body, has captured hearts thanks to TikTok and the popular video game Minecraft, which added the salamander to its universe in 2021.

The Mexican axolotl — a dusky amphibian with the remarkable habit of neoteny, or retaining its juvenile body type all its life — once thrived in these canals. Though axolotls have been ...