Description
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).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: United States

U.S. state distribution from AmphibiaWeb's database: North Carolina

View distribution map in BerkeleyMapper.

This species is endemic to the Neuse and Tar-Pamlico River drainages in North Carolina. This species requires high water oxygen content and quality (Ashton 1990; Petranka 1998). Preferred habitat is streams with channels over 15 m wide and 1 m deep (Braswell and Ashton 1985). Animals may be found in areas with clay or hard soil substrate or leaf beds (Petranka 1998).

Life History, Abundance, Activity, and Special Behaviors
Partial courtship has been described. Mating occurs from December through March and possibly April or May. Females oviposit beneath large rocks in fast current during April and May. One nest has been found consisting of 35 eggs attended by a male. It is not clear whether the male was protecting the eggs. Animals are active away from cover at night. During the day they retreat to streambank burrows or cavities under large rocks. Retreats may be constructed by shoveling sand and gravel with the snout. Animals are less active when stream temperatures are high, over 18ºC. Diet includes ostracods, copepods, mayflies, beetles, earthworms, cladocerans, snails, and isopods. Adults tend to eat larger items including slugs, leaches, hellgrammites, fish, salamanders, and small snakes (Ashton 1985; Cooper and Ashton 1985; Ashton and Braswell 1979). Fish are potential predators, but the skin of N. lewisi produces noxious secretions and may defend against predation (Neill 1963; Braswell and Ashton 1985; Petranka 1998).

Trends and Threats
Populations have been found throughout the range of the species, but in areas with pollution few or no specimens were found (Braswell and Ashton 1985).

Relation to Humans
Mudpuppies and waterdogs are sometimes seen in the pet trade.

Comments
Necturus lewisi and N. punctatus may be sister species (Guttman et al. 1990).

This species was featured as News of the Week on 8 October 2018:

Amphibians have some of the largest and smallest known genomes of all tetrapods. Liedtke et al. (2018) shows that, although genome size is incredibly variable across amphibians, the majority of amphibian genome size evolution has occurred gradually over time. The best supported evolution model for genome size shows a single jump in size occurring as genome size increased in the ancestor of salamanders. Salamanders have the largest amphibian genomes, with the Neuse River Waterdog (Necturus lewisi) holding the title for largest tetrapod genome size (140 pg)! Furthermore, they found no support for the hypothesis that amphibian genome size evolves in association with changes in development (shifts such as changes from larval to direct development) but did see an association between genome size and length of development and climate (temperature and humidity). Despite amphibians having the widest range of tetrapod genome sizes, the evolution of genome size in this group can be largely explained by random, gradual change over time and appears to have little to do with the drastic changes in development that have repeatedly evolved within amphibians (Written by Molly Womack).

References

Ashton, R. E., Jr. (1985). "Field and laboratory observations on microhabitat selection, movements, and home range of Necturus lewisi (Brimley)." Brimleyana, 10, 83-106.

Ashton, R. E., Jr. (1990). ''Necturus lewisi Brimley. Neuse River Waterdog.'' Catalogue of American Amphibians and Reptiles. Society for the Study of Amphibians and Reptiles, 456.1-456.2.

Ashton, R. E., Jr., and Braswell, A. L. (1979). ''Nest and larvae of the Neuse River Waterdog, Necturus lewisi (Brimley) (Amphibia: Proteidae).'' Brimleyana, 1, 15-22.

Braswell, A. L., and Ashton, R. E., Jr. (1985). ''Distribution, ecology, and feeding habits of Necturus lewisi (Brimley).'' Brimleyana, 10, 13-35.

Cooper, J. E., and R. E. Ashton, Jr. (1985). "The Necturus lewisi study: Introduction, selected literature review, and comments on the hydrologic units and their faunas." Brimleyana, 10, 1-12.

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.

Neill, W. T. (1963). "Notes on the Alabama waterdog, Necturus alabamensis Viosca." Herpetologica, 19, 166-174.

Petranka, J. W. (1998). Salamanders of the United States and Canada. Smithsonian Institution Press, Washington D.C. and London.

Species Account Citation: AmphibiaWeb 2019 Necturus lewisi: Neuse River Waterdog <https://amphibiaweb.org/species/4225> University of California, Berkeley, CA, USA. Accessed Nov 24, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 24 Nov 2024.

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