While often confused, axolotls and mudpuppies are distinct aquatic salamanders with unique characteristics. This article clarifies their identities by highlighting the features that set them apart.
The Unique Axolotl
The axolotl, scientifically known as Ambystoma mexicanum, is a mole salamander native to the ancient lake system of Xochimilco and surrounding canals in Mexico City. This amphibian exhibits neoteny, maintaining its larval features throughout its entire life, including external gills, a dorsal fin, and an aquatic lifestyle. It never undergoes metamorphosis into a terrestrial adult form.
Axolotls typically grow to lengths of 6 to 18 inches and can weigh between 2 to 8 ounces. They have a flat head, a long tail, and four lizard-like limbs, with five toes on their hind feet. While often seen in captive breeding in vibrant colors like pink, gold, or white, wild axolotls are usually darker, ranging from black, brown, or gray, sometimes with small spots. These carnivorous creatures primarily feed on mollusks, worms, insects, and small fish, using suction to capture their prey. The axolotl is critically endangered in the wild due to habitat destruction, water pollution, and the introduction of invasive species.
Meet the Mudpuppy
The mudpuppy (Necturus maculosus) is an intriguing aquatic salamander belonging to the family Proteidae. Found across eastern North America, from southern Canada down to Georgia, they inhabit lakes, rivers, and ponds. Mudpuppies are entirely aquatic, spending their entire lives underwater and relying on their prominent, bushy external gills for respiration, as their skin and lungs alone are insufficient for gas exchange.
Mudpuppies are generally larger than axolotls, averaging 13 inches, with some individuals growing over 17 inches. Their bodies are typically rusty brown or gray, often adorned with blackish-blue spots, which gives them their scientific name, maculosus, meaning “spotted”. They possess four toes on each of their four well-developed limbs. These nocturnal, opportunistic carnivores consume insects, mollusks, worms, and small fish. The name “mudpuppy” is thought to derive from the misconception that they bark, though they are silent.
Unpacking the Differences: Axolotl vs. Mudpuppy
While both axolotls and mudpuppies share a superficial resemblance due to their permanent external gills and aquatic lifestyles, they are distinct species with significant differences. Taxonomically, they belong to different families and genera: axolotls are mole salamanders (Ambystoma mexicanum), while mudpuppies are waterdogs (Necturus maculosus).
Their geographic origins are also vastly separate. Axolotls are endemic to a specific lake system in Mexico, whereas mudpuppies are widespread across eastern North America.
A key distinction lies in their developmental biology. Axolotls exhibit neoteny, meaning they retain larval characteristics into adulthood but are capable of metamorphosing under specific, though rare, conditions. Mudpuppies, in contrast, are perpetually larval salamanders, meaning they never undergo metamorphosis and remain in a permanent larval state throughout their lives.
Subtle physical differences also exist. Axolotls typically have more feathery gills that can be pink to dark red, and they possess five toes on their hind feet, distinguishing them from mudpuppies which have four toes on all feet. While axolotls are known for their vibrant color variations in captivity, wild mudpuppies generally display duller shades of brown or gray. The axolotl is critically endangered in the wild, facing severe population decline, while the common mudpuppy’s population is considered stable and of least concern.