Amphiuma tridactylum

Amphiuma tridactylum: The Three-Toed Amphiuma

Amphiuma tridactylum, known commonly as the three-toed amphiuma, is a species of aquatic salamander found in the Southeastern United States. Its appearance is notably eel-like, with an elongated body that is typically dark gray-black or brown. The species possesses tiny, vestigial legs, each featuring three toes, and small, lidless eyes. A significant biological characteristic is its possession of the largest recorded red blood cells of any animal.

Distribution and Habitat

The geographic range of the three-toed amphiuma extends across the Gulf of Mexico states from Alabama to Texas, and northward into Missouri, Arkansas, Tennessee, and Kentucky. It is frequently found in bottomland marshes and lakes, seeps, bayous, cypress sloughs, and streams, particularly in areas with limestone bedrock. This species often occupies crayfish burrows and can also be found in manmade ditches.

Behavior and Diet

Amphiuma tridactylum exhibits nocturnal and carnivorous behavior. It spends the majority of its time concealed within densely vegetated sections of permanent, slow-moving water bodies such as swamps, ponds, and lakes. While primarily aquatic, they may emerge from the water following significant rainfall. Their diet is broad, encompassing earthworms, fish, other amphibians, small reptiles, crustaceans (especially crayfish), and various small invertebrates like insects and snails. Due to this varied diet, amphiumas are often caught as bycatch by fishermen.

Reproduction

This species engages in internal fertilization, a characteristic that distinguishes it from some other amphiumas. The mating period occurs from December to June, followed by nesting from April to October. Females lay approximately 200 eggs in a single strand, typically deposited in an underwater cavity. Male amphiumas possess specialized cloacal glands that may facilitate mating with multiple females in succession, contributing to a polygynous reproductive dynamic.