Comprehensive DescriptionRead full entry
Completely aquatic and gilled throughout life. Among mudpuppies and waterdogs (genus Necturus), this species is medium-sized. All mudpuppies and waterdogs have bushy external gills, two gill slits, a laterally compressed tail, and four toes on front and hind feet. Adult N. lewisi are 9-17 cm snout to vent length (16.5-28 cm total length). The dorsum is rusty brown with numerous, large bluish or black spots or blotches. Spots tend to be smaller on the head. The venter is dull brown to gray also with smaller spots. Spots on N. lewisi are larger but less numerous than on N. maculosus. The snout is dorsally compressed. Sexually mature males can be distinguished by the swollen cloaca and pair of enlarged cloacal papillae that project posteriorly. Hatchlings are 15-16 mm snout to vent length (22-24 mm total length). The venter of larvae is unspotted in contrast to the pigmented sides and back. In larvae up to 41 mm snout to vent length, there is a broad, light tan dorsal stripe, usually flanked by darker lateral stripes, extending from the head to the tail. Lateral stripes fade with age (Ashton 1990; Petranka 1998).