Amphiuma is a small genus of fully aquatic salamanders native to the freshwater wetlands, swamps and slow-moving waters of the southeastern United States. These animals are unmistakable for their long, eel-like bodies, smooth skin and very small, paddle-like limbs. Each limb bears a reduced number of toes—one, two or three—a convenient field mark reflected in common names such as one-toed, two-toed and three-toed amphiuma. They make up the single living genus in the family Amphiumidae and are amphibians, not fish.

Physical characteristics and physiology

Adults are relatively large for salamanders and use rib and body undulations to swim. Although aquatic for most or all of their lives, amphiumas breathe with well-developed lungs and can absorb gases through their skin and oral membranes. Larval amphiumas have external gills, but these are lost as they metamorphose to the adult form. The very large amount of DNA in amphiuma cells has attracted scientific attention; their genome size is among the largest reported for vertebrates, a feature often linked to abundant repetitive and non-coding sequences (source).

Taxonomy and species

Modern classifications place Amphiuma in the order Caudata (salamanders). The genus contains a few recognized species, commonly cited by toe count and scientific names such as Amphiuma tridactylum, Amphiuma means and Amphiuma pholeter. For general overviews of aquatic salamanders and comparative information, see resources on aquatic amphibians and field guides (further reading). The genus name and taxonomic history are discussed in specialist works and museum treatments (Amphiuma entries).

Behavior, diet and life history

Amphiumas are largely nocturnal and secretive. They feed on fish, crustaceans (especially crayfish), aquatic insects and smaller amphibians, using a sit-and-wait or ambush strategy among submerged vegetation and leaf litter. Reproduction typically involves eggs laid in hidden, moist cavities or nests; females often guard eggs and developing larvae. Amphiumas can tolerate seasonal drying by burrowing into mud and entering a dormant state until water returns.

Conservation and human interactions

While not globally endangered, amphiuma populations depend on healthy wetland habitats and can be affected by drainage, pollution and habitat fragmentation. They are encountered occasionally by anglers and collectors, and are sometimes kept in captivity by experienced aquarists because of their size and specialized aquatic requirements. Conservation efforts emphasize protection of slow-water wetlands and water-quality management to support amphibian communities.

  • Common names: often misleadingly called "conger eels" or "congo snakes" though they are salamanders.
  • Field ID: toe count (1, 2, or 3) is a practical diagnostic feature.
  • Genomic interest: notable for very large genome size among vertebrates (genome studies).
  • Resources: consult field guides and amphibian biology texts for regional details (regional resources, taxon accounts).