Two subspecies are currently recognized which differ in geographic distribution (see below) and coloration. The mudpuppy (N. m. maculosus, sometimes called the common mudpuppy) is rusty brown to grey dorsally, with a gray venter that ranges from unspotted to densely spotted. The Red River mudpuppy (N. m. louisianensis, sometimes called the Louisiana mudpuppy or waterdog) is light yellowish brown to tan dorsally, sometimes with a dark dorsal stripe bordered by lighter stripes. The back and sides of the belly have large dark spots or blotches, but the midline of the venter is light colored with no spots (Conant and Collins 1991; Petranka 1998).
A genetic survey found little divergence between populations of mudpuppies from Massachusetts, Minnesota, and North Carolina (Ashton et al. 1980). Necturus beyeri, N. alabamensis, and N. maculosus are relatively closely related (Guttman et al. 1990).
- Ashton, R. E., Jr., Braswell, A. L. and Guttman, S. I. (1980). ''Electrophoretic analysis of three species of Necturus (Amphibia: Proteidae), and the taxonomic status of Necturus lewisi (Brimley).'' Brimleyana, 4, 43-46.
- Conant, R. and Collins, J. T. (1991). A Field Guide to Reptiles and Amphibians: Eastern/Central North America. Houghton Mifflin, Boston.
- Guttman, S. I., Weigt, L. A., Moler, P. E., Ashton, R. E., Jr., Mansell, B. W. and Peavy, J. (1990). ''An electrophoretic analysis of Necturus form the southeastern United States.'' Journal of Herpetology, 24(2), 163-175.
- Petranka, J. W. (1998). Salamanders of the United States and Canada. Smithsonian Institution Press, Washington and London.
- Pfingsten, R. A., and White, A. M. (1989). ''Necturus maculosus (Rafinesque). Mudpuppy.'' Salamanders of Ohio. Pfingsten, R. A., and F. L. Downs, eds., Ohio Biological Survey, Columbus, OH, 71-78.
- Shoop, C. R. (1965). "Aspects of reproduction in Louisiana Necturus populations." American Midland Naturalist, 74, 357-367.