Amphibians
Three-toed Amphiuma
Amphiuma tridactylum · also called three-toed amphiumas, Congo eel
A three-toed amphiuma looks almost exactly like an eel, gliding through swamp water with legs so reduced they barely register as limbs at all. Pick one up carelessly, though, and it will remind you it is still a salamander with real teeth, delivering a bite sharp enough to genuinely surprise anyone expecting a harmless, defenceless animal.
Overview
The three-toed amphiuma, Amphiuma tridactylum, is the largest of the three amphiuma species, an eel-like salamander of swamps, ditches, and ponds across the south-central United States. It hunts crayfish, small fish, and worms at night, spending most of its time hidden in mud and dense aquatic vegetation.
Nearly legless, genuinely toothy
Its four tiny, three-toed limbs provide little function beyond marking its salamander ancestry, with swimming powered almost entirely by side-to-side body movement. Unlike fully neotenic salamanders, it develops lungs as an adult but still relies heavily on skin respiration in low-oxygen wetland water.
Status
Least Concern — common and widespread across suitable freshwater wetland habitat throughout its range, tolerating a variety of still and slow-moving water conditions.
Three-toed Amphiuma: common questions
How is the three-toed amphiuma different from the two-toed amphiuma?
The most direct distinguishing feature is the number of toes on each of the four tiny, reduced limbs, with the three-toed amphiuma having three toes per foot compared with the two-toed amphiuma's two, and the three-toed species also tends to grow considerably larger, making it the biggest of the three recognised amphiuma species found in the southeastern and south-central United States.
Why does the three-toed amphiuma have such tiny, seemingly useless legs?
The species has evolved an overwhelmingly aquatic, eel-like lifestyle relying on side-to-side body undulation for swimming rather than walking, and over evolutionary time its four limbs have become greatly reduced in size and function accordingly, retaining just enough structure to reflect its ancestry as a four-limbed salamander without providing much practical use for actual locomotion on land or in water.
Is it true that this eel-like animal can actually bite hard?
Yes, despite its smooth, limbless-looking, harmless appearance, the three-toed amphiuma has sharp teeth adapted for gripping slippery prey such as fish and crayfish, and it can deliver a surprisingly painful bite if handled carelessly or provoked, a defensive capability that often catches people off guard given how harmless the animal looks at first glance.
Does the three-toed amphiuma breathe through gills like an axolotl?
No, unlike fully neotenic salamanders such as the axolotl that retain external gills throughout adulthood, the three-toed amphiuma develops lungs and loses its external gills as it matures, though it still relies significantly on absorbing additional oxygen through its skin, an adaptation useful in the often low-oxygen, vegetation-choked wetland water it typically inhabits.