Ambystoma mexicanum

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Taxonomy

• Kingdom: Animalia
• Phylum: Chordata
• Class: Amphibia
• Order: Urodela (Caudata)
• Family: Ambystomatidae
• Genus: Ambystoma
• Species: Ambystoma mexicanum

Common Names by Region

• Axolotl
• Mexican Walking Fish (misleading common name)
• Water Dog (colloquial, shared with other salamanders)
• Ajolote (Spanish, from Nahuatl āxōlōtl)

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Description

General Appearance

The wild-type axolotl displays a mottled olive, brown, and gray coloration with subtle speckling—designed for camouflage in murky lakebeds. The body is soft, elongated, and fully aquatic, with a broad head and lidless eyes.

Size

Typically 6–12 inches (15–30 cm) in captivity, though growth depends on conditions and feeding.

Distinguishing Features

• Prominent external feathery gills (usually pink to purplish)
• Dorsal fin extending from mid-back through the tail
• Wide, flat head with a gentle expression
• Fully aquatic, neotenic adult form (retains larval traits permanently)
• Lack of eyelids

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Known Range

Native exclusively to the lake system of:

• Lake Xochimilco (and historically Lake Chalco) in central Mexico

Wild populations are now critically endangered, surviving only in fragmented canal systems.

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Care / Habitat

In the wild:

• Cool, slow-moving freshwater canals
• Dense aquatic vegetation
• Silty or muddy substrate

In captivity:

• Temperature: 60–68°F (critical—heat stress above ~72°F)
• Water: Clean, low ammonia/nitrite, gentle flow
• Substrate: Fine sand or bare bottom (to avoid impaction)
• Cover: Rocks, driftwood, plants

Axolotls are ambush predators and prefer low-light, structured environments.

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Propagation / Reproduction

• Breeding triggered by seasonal cooling and photoperiod changes
• Males deposit spermatophores, females pick them up
• Eggs are laid individually on plants or surfaces
• Hatch into free-swimming larvae

Unlike most salamanders, axolotls do not naturally metamorphose under normal conditions.

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Pests / Diseases / Threats

• Fungal infections (often linked to poor water quality)
• Ammonia/nitrite toxicity
• Heat stress
• Ingestion of inappropriate substrate
• In the wild: habitat loss, pollution, invasive fish species

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Additional Notes

The axolotl is one of the most important organisms in biological research due to its:

• Extreme regenerative ability (limbs, spinal cord, heart tissue)
• Stable neotenic state (retention of juvenile traits into adulthood)

The wild-type coloration seen here is closest to the original natural form, in contrast to common captive morphs (leucistic, albino, melanoid, etc.).

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Maintenance / Management

• Maintain strict temperature control
• Perform regular water testing and partial changes
• Feed appropriately sized prey (worms, pellets, soft-bodied foods)
• Avoid tankmates that may nip gills
• Monitor for stress indicators (curling gills, floating, loss of appetite)