As amphibians go, axolotls are pretty cute. These salamanders sport a Mona Lisa half-smile and red, frilly gills that make them look dressed up for a party. You might not want them at your soiree, though: They’re also cannibals. While rare now in the wild, axolotls used to hatch en masse, and it was a salamander-eat-salamander world. In such a harsh nursery, they evolved — or maybe kept — the ability to regrow severed limbs.
“Their regenerative powers are just incredible,” says Joshua Currie, a biologist at the Lunenfeld-Tanenbaum Research Institute in Toronto who’s been studying salamander regeneration since 2011. If an axolotl loses a limb, the appendage will grow back, at just the right size and orientation. Within weeks, the seam between old and new disappears completely.
And it’s not just legs: Axolotls can regenerate ovary and lung tissue, even parts of the brain and spinal cord.
The salamander’s exceptional comeback from injury has been known for more than a century, and scientists have unraveled some of its secrets. It seals the amputation site with a special type of skin called wound epithelium, then builds a bit of tissue called the blastema, from which sprouts the new body part. But until recently, the fine details of the cells and molecules needed to create a leg from scratch have remained elusive.
With the recent sequencing and assembly of the axolotl’s giant genome, though, and the development of techniques to modify the creature’s genes in the lab, regeneration researchers are now poised to discover those details. In so doing, they’ll likely identify salamander tricks that could be useful in human medicine
