Necturus

Necturus is a genus of aquatic salamanders endemic to the eastern United States and Canada. They are commonly known as waterdogs and mudpuppies. The common mudpuppy (N. maculosus) is probably the best-known species – as an amphibian with gill slits, it is often dissected in comparative anatomy classes. The genus is under scrutiny by herpetologists. The relationship between the species is still being studied. Most recently, the Red River mudpuppy (N. louisianensis) was elevated to full species status, after being considered only a subspecies of the common mudpuppy (N. maculosus), but not all herpetologists agree on this change. There are seven species: The AmphibiaWeb lists only five species, not recognizing N. lodingi and N. louisianensis as distinct species. Two known fossil species, N. krausei and an unnamed species, are respectively known from the Paleocene of Saskatchewan and from Florida during the Pleistocene. Necturus are paedomorphic: adults retain larval-like morphology with external gills, two pairs of gill slits, and no eyelids. They are moderately robust and have two pairs of short but well-developed limbs and a large, laterally compressed tail. Lungs are present but small. Typical adult size is 20–25 cm (8–10 in) in total length, but Necturus punctatus is larger and may reach 40 cm (16 in). Necturus occur in surface waters, preferentially with clear water and rocky substrates without silt. They forage during the night and eat a variety of prey, but have preference for crayfish.