Axolotl (Ambystoma mexicanum) Fact Sheet: Physical Characteristics

Body measurements

Data sources: Gresens (2004); Griffiths, Bride, et al. (2004); Pasmans (2014); SEMARNAT (2018)

Body

• Large, stout body (Pasmans et al. 2014)
• Wide trunk (Sciences et al. 2006)

Head

• Large head with wide-set eyes (Wanderer 2018)
• External gills (Gresens 2004)
• Prominent, branch-like
• Feathery filaments for gas exchange
• Also have lungs to occasionally breathe at the surface
• Teeth
• Tiny and blunt (Gresens 2004)
• Single row of small teeth (Clemen and Greven 2015)
• Used to capture food, but not tear or chew it (Fenske et al. 1995 cited by de Jesus Chaparro-Herrera et al. 2011)

Tail

• Well-developed, eel-like tail (Pasmans et al. 2014; SEMARNAT 2018)
• Used for swimming (Gresens 2004)

Coloration

• Paedomorph (form with juvenile traits)
• Wild individuals: range from black to dark brown with black spots (Pasmans et al. 2014)
• Managed care: many colors, including white, golden, multicolored, and albino (Newth 1960; Bukowski et al. 1990; Gresens 2004; Pasmans et al. 2014)
• Metamorph
• Dark color with speckle-like spots (Brandon 1989)

Lateral line

• Nerve fibers along head and body that detect water movement and vibrations (Bartels et al. 1990; Münz and Claas 1991)

Regeneration of body parts

• Able to regenerate tissues and entire body parts (e.g., Wanderer 2018; Reiß 2022)
  • Regrow limbs, tails, organs, parts of the eye and brain (e.g., Satoh et al. 2008; Lee and Gardiner 2012; Thompson et al. 2014; Vance 2017; Wanderer 2018)

Other notable abilities

• Produce stem cells, allowing for limb and tissue regeneration (e.g., Smith 1964; Sutasurja and Nieuwkoop 1974)
• Low incidence of cancer and resistance to tumor growth (Bölük et al. 2022)
  • Appears to have resistance to carcinogens
• Also see Relationship with humans

Temperature tolerance

• Appears to have a high temperature tolerance of nearly 38°C (100°F) (e.g., Orille et al. 2020) — but likely lose body mass at very high or low temperatures (Enríquez García et al. 2009; Panessiti et al. 2021)

Most axolotls retain juvenile traits, like a prominent tail fin and feathery gills, into adulthood.

This life history strategy, known as paedomorphy, benefits salamanders that evolved in permanent bodies of water, like those historically found in Central Mexico. Paedomorphy evolved multiple times among the axolotl's close relatives, the mole salamanders (Family Ambystomatidae).

Under some conditions, axolotls go through metamorphosis — but how commonly this occurs in the wild isn't known.

Image credits: © John P. Clare via Flickr (embryo, hatchling, adult). Some rights reserved.

A wild axolotl's skin typically matches the dark brown color of its muddy lake home. But axolotls bred in managed care can be many colors: white, golden, multicolored, or albino.

The first white mutant axolotl appeared in Paris in the late 1860s.

People sometimes breed axolotls with tiger salamanders, yielding still more varied color and skin patterns.

Image credit: © San Diego Zoo Wildlife Alliance. All rights reserved.