Rough-skinned Newt, Roughskin Newt, Northern Rough Skin Newt, Crater Lake Newt
Gerald and Buff Corsi
© 2007 California Academy of Sciences (1 of 134)
Taricha granulosa may be distinguished from T. torosa by the V-shaped pattern of the palatine teeth (compared to Y-shaped), dark lower eyelid, and less protruberant eyes. These species also differ in their defensive posture (see below) (Stebbins 1985).
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Canada, United States
U.S. state distribution from AmphibiaWeb's database: Alaska, California, Idaho, Montana, Oregon, Washington
Canadian province distribution from AmphibiaWeb's database: British Columbia
Populations in Idaho are considered introduced by the Idaho State Department of Fish and Game (https://idfg.idaho.gov/species/taxa/15503).
Life History, Abundance, Activity, and Special Behaviors
While T. granulosa is the most toxic newt in North America, all species of Taricha possess the potent neurotoxin known as tetrodotoxin. This serves the newt as an antipredator defense, and is also harmful to humans (Brodie et al. 1974; Petranka 1998). Despite their toxicity, newts are subject to predation by racoons and garter snakes (Thamnophis.) Thamnophis sirtalis is a specialist predator on newts and has evolved resistance to the tetrodotoxin (Brodie and Brodie 1990; Petranka 1998; Motychak et al. 1999). When harassed, Taricha assume the “unken reflex” where the head is raised, the tail is turned up and held straight over the body, the limbs are extended, and the eyes are closed (Riemer 1958; Brodie 1977). This action exposes the bright aposomatic coloration found on the newt's belly. The exact pattern of this reflex is a species-specific character, distinguishable from sympatric T. torosa, which holds the tail straight, while T. granulosa curls the tip (Stebbins 1985; Petranka 1998).
Trends and Threats
Relation to Humans
This species was featured in the News of the Week, 11 May 2020:
Many salamandrids possess tetrodotoxin (TTX), the same neurotoxin found in pufferfish. Although TTX in marine animals derives from symbiotic bacteria or diet, the source in amphibians has been controversial. Populations of rough-skinned newts (Taricha granulosa) possess different amounts of TTX due to the evolution of TTX resistance in populations of predatory garter snakes. Vaelli et al. (2020) examined the skin microbiome in high- and low-TTX populations of newts and found that bacterial diversity was lower in the highly toxic population, suggesting their skin microbiota is tightly regulated. Several strains of bacteria, particularly Pseudomonas, cultured from the skin of toxic newts were shown to produce TTX in the lab, and Pseudomonas were significantly more abundant in toxic than non-toxic newts. The ability of rough-skinned newts to resist TTX appears to derive from mutations in the target of the toxin, voltage-gated sodium channels (NaVs); all six NaV genes possess mutations in the TTX-binding region of the channel, and electrophysiological experiments with the most widely expressed channel (NaV1.6) verify the mutations confer resistance to almost infinite concentrations of TTX. They show an important role that symbiotic microbes play in the physiology and evolution of their multicellular hosts. (Heather Eisthen and Patric Vaelli)
This species was featured in the News of the Week, 4 April 2016:
The Rough-skinned Newt, Taricha granulosa, is engaged in an evolutionary arms race with its only known significant predator, the Common Garter Snake, Thamnophis sirtalis. In regions where snakes are absent (such as some islands near Vancouver Island, Canada), newt toxicity is low to absent, whereas in sites where toxicity-resistant snakes are common (various sites in California and Oregon), newt toxicity is high to very high. The authors of a new paper (Hague et al. 2016) studied newts in southeast Alaska, where snakes are absent, and as expected, toxicity levels were low at most sites examined. However, puzzling variation was found. In one lake on Wrangell Island, no toxicity was found, but newts from another lake on the same island displayed surprisingly high levels, rivaling those in some areas where snake predators have high toxin resistance. Various explanations are offered, but reciprocal selection does not fully explain the toxicity variation in newts (David B. Wake).
See another account at californiaherps.com.
Aubry, K. B., and Hall, P. A. (1991). ''Terrestrial amphibian communities in the southern Washington Cascade Range.'' Wildlife and Vegetation of Unmanaged Douglas-fir Forests, General Technical Report PNW-GTR-285. Ruggiero, L. F., Aubry, K. B., Carey, A. B., and Huff, M. H., technical coordinators, eds., USDA Forest Service, Northwest Research Station, Olympia, Washington., 326-338.
Brodie, E. D., III, and Brodie, E. D., Jr. (1990). ''Tetrodotoxin resistance in garter snakes: An evolutionary response of predators to dangerous prey.'' Evolution, 44, 651-659.
Brodie, E. D., Jr. (1977). "Salamander antipredator postures." Copeia, 1977, 523-535.
Brodie, E. D., Jr., Hensel, J. L., and Johnson, J. A. (1974). ''Toxicity of the urodele amphibians Taricha, Notophthalmus, Cynops, and Paramesotriton (Family Salamandridae).'' Copeia, 1974(2), 506-511.
Corn, P. S. and Bury, R. B. (1991). ''Terrestrial amphibian communities in the Oregon Coast Range.'' Wildlife and Vegetation of Unmanaged Douglas-fir Forests, General Technical Report PNW-GTR-285. K. Ruggiero, B. Aubry, A. B. Carey, and M. H. Huff, technical coordinators, eds., USDA Forest Service, Pacific Northwest Research Station, Olympia, Washington., 304-317.
Motychak, J. E., E. D. Brodie, Jr., and E. D. Brodie, III (1999). "Evolutionary response of predators to dangerous prey: Preadaptation and the evolution of tetrodotoxin resistance in garter snakes." Evolution, 53, 1528-1535.
Nussbaum, R. A., and Brodie, E. D., Jr. (1981). ''Taricha granulosa (Skilton). Rough-skinned Newt.'' Catalogue of American Amphibians and Reptiles. Society for the Study of Amphibians and Reptiles, 272.1-272.4.
Petranka, J. W. (1998). Salamanders of the United States and Canada. Smithsonian Institution Press, Washington and London.
Riemer, W. J. (1958). "Variation and systematic relationships within the salamander genus Taricha." University of California Publications in Zoology, 56(3), 301-390.
Stebbins, R. C. (1985). A Field Guide to Western Reptiles and Amphibians. Houghton Mifflin, Boston.
Stebbins, R.C. (1951). Amphibians of Western North America. University of California Press, Berkeley.
Written by Meredith J. Mahoney (molge AT yahoo.com), Museum of Vertebrate Zoology, UC Berkeley
First submitted 2000-07-28
Edited by M. J. Mahoney, Kevin Gin (12/03); updated Ann T. Chang, Michelle S. Koo (2020-05-14)
Species Account Citation: AmphibiaWeb 2020 Taricha granulosa: Rough-skinned Newt <http://amphibiaweb.org/species/4288> University of California, Berkeley, CA, USA. Accessed Jun 3, 2020.
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Citation: AmphibiaWeb. 2020. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 3 Jun 2020.
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