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Photo credit: N. Thach & M. Lang.
Comparative Anatomy Guide to Amphiuma tridactylumCreated By: Misty Lang and Nina Thach with assistance and edits from Dr. Heidi Schutz


Amphiuma are nocturnal salamanders that reside in the bottom of lakes and swamps. They are known for their elongated body and four vestigial limbs that have no significant function but have remained as an evolutionary remnant.

  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Amphibia
  • Order: Caudata
  • Family: Amphiumidae
  • Genus: Amphiuma
  • Species: tridactylum

Common Names:

Three-toed Amphiuma, Congo eel, Congo snake, ditch eel, conger eel, lamprey, lamp-eater, lamp eel, lamprey eel (P‍‍‍‍‍‍‍‍‍etranka 1998‍‍‍‍‍‍‍‍‍).

Distribution and Habitat:

Amphiuma tridactylum can be found in the southern United States between east Texas to west Alabama, and as far north as Missouri and west Kentucky (Fig. 1). Their preferred habitat tends to be highly vegetated areas such as lakes, ponds, bayous, streams, sloughs, swamps, and drainage ditches (‍‍‍‍‍‍‍‍‍Bishop 1943,‍‍‍‍‍‍‍‍‍ Petranka 1998).


Figure 1. A. tridactlyum distribution in United States after Petranka 1998. Created by N. Thach by modification of Blank USA map from Wikemedia commons. by Lokal_Profil under CC-BY-SA-2.5 image


A. tridactylum are nocturnal feeders with a diet primarily of crayfish and earthworms. They are also known to consume fish, insects, spiders, snails, ground kins, and vegetation (Petranka 1998).

Physical Description:

A. tridactylum has an elongated body (Fig. 2). Whereas the specimen we studied was approximately 68 centimeters long, some have been recorded to be a meter in length. A. tridactylum has four limbs approximately four millimeters long, with three digits on every limb. The color of their skin varies from brown, grey, and black in appearance. Internal organs are also elongated as shown in Figure 2.

Figure 2. Amphiuma organs externalized. Photo credit: M. Lang & N. Thach. Editing credit: N. Thach.


As predators, A. tridactylum hides in vegetation until prey approaches, and darts out quickly, ambushing their prey with a bite. It thrashes the prey from side to side repeatedly. As for sexual behavior, the mating season occurs from the beginning of January through May, peaking in March. Females reproduce every two years, while males do so every year. Courting can involve large groups of A. tridactylum in shallow pools (‍‍‍‍‍‍‍‍‍Petranka 1998‍‍‍‍‍‍‍‍‍).

System Descriptions:


Bishop, S. C. (1943). Handbook of salamanders: The salamanders of the United States, of Canada, and of Lower California. Ithaca, New York: Comstock Pub. Co., 131, 136-137 p.

Petranka, J. W. (1998). Salamanders of the United States and Canada. Washington: Smithsonian Institution Press. 54 p.