Re-growing Limbs: The Superpower of the Axolotl

Axolotls, or Mexican salamanders, are a fascinating amphibian species that in the wild, lives only on the southern edge of Mexico City in canals and wetlands. But you can see one in the OKC Zoo’s Herpetarium!  

 In general, amphibians are hatched from eggs as aquatic larvae (called tadpoles in frogs, a relative of the axolotl) and then undergo stages of body transformations until they reach their adult form. Axolotls are different  in that they retain their larval form, and retain gills for breathing.

 Axolotls are also unique because they have a “superpower”. They can regenerate a completely functional limb after injury. The Zoo’s vet team witnessed this incredible feat for the first time in OKC Zoo history when, in late 2016, the keepers discovered one of the axolotl with an arm injury.  Due to extensive skin and bone damage, the vet team decided to anesthetize the axolotl to amputate the arm.  Axolotls can receive anesthesia in a water bath using the same medication used to anesthetize fish since both receive oxygen from the water through their gills.  Just as a person inhales gas anesthesia, fish and axolotls “inhale anesthesia dissolved in their water.  

 Our team successfully removed the arm, but did not suture the skin closed so that we would not interfere with the potential regeneration of the arm. Although our understanding of pain  in many species is limited, we could only assume this injury and  surgery could be painful. The vet team gave the axolotl an anti-inflammatory and an opioid pain medication similar to those used in human and domestic animal medicine. The amputation site healed remarkably fast, and now we are watching its superpower at work.  Due to great animal care and a little luck, Zoo staff members and guests have been able to happily watch this animal regenerate a new arm! 

Left arm injury of an axolotl at the Oklahoma City Zoo.

 

Photo of the axolotl after surgical amputation of the injured limb on 10/24/16

Initial regeneration of the amputated left arm in an axolotl as of 1/9/17.

 Updated photo of the regeneration of the amputated axolotl left arm on 4/1/17.

 

--Lynnette Waugh, Zoo veterinary resident

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