Mudpuppies or waterdogs are aquatic salamanders of the family Proteidae. Their name originates from the misconception that they make a dog-like barking sound. The range of the genus Necturus runs from southern central Canada, through the midwestern United States, east to North Carolina and south to Georgia and Mississippi. The range of the olm, the only extant member of the genus Proteus, is limited to the Western Balkans.

Proteidae, is divided into two extant genera, Necturus with five North American species, and Proteus with one European species. They represent an ancient group, known from fossils since the Miocene.

Family Proteidae

In contrast to many salamanders, mudpuppies never lose their gills during maturation from larvae. This aspect of their physiology is known as pedomorphosis. Despite having lungs, which appear to provide little use in respiration, mudpuppies spend their entire lives underwater. The adult gills resemble fish gills in many ways, but differ from fish gills in that they are external and lack any form of operculum or covering. The bright red exposed gills are often found closed against the body in cool, highly oxygenated water. In warmer, poorly oxygenated water, the gills expand to increase water circulation and provide greater surface area for oxygen intake. Mudpuppies also absorb oxygen through their skin and by occasionally breathing air at the surface.