Comprehensive DescriptionRead full entry
A large, eel-like aquatic salamander. All four limbs are present, but extremely tiny, and there are only two toes on each. As in other species of Amphiuma (Family Amphiumidae), there is a single gill slit, no external gills, and the eyes are lidless (Petranka 1998). Adult two-toed amphiumas range in size from 46 - 116 cm total length. There are 57 - 60 costal grooves (average 58). The laterally compressed tail is 20-25% of the total body length. The dorsum is black to dark brown or grey and the venter is only slightly lighter (Salthe 1973; Petranka 1998). A dark patch on the chin is difficult to see against the ground coloration (Salthe 1973). Hatchlings are about 55 mm total length and all four limb are functional at the time of hatching. Gills are resorbed almost immediately after hatching. Juveniles are similar in color to adults. See Petranka (1998) and references therein.
The three species of Amphiuma are similar but can be differentiated based on the number of toes (one, two, or three), coloration, and body size.
Amphiuma means and A. tridactylum are genetically similar, while A. pholeter is quite distinct and represents an ancient evolutionary offshoot (Karlin and Means 1994). Some authors have argued that A. means and A. tridactylum should be treated as conspecifics. These species, which are sympatric over much of their ranges, differ in coloration, number of toes, and some body proportions. See Salthe (1973) for discussion of this issue.