Taricha granulosa (Skilton, 1849)
Rough-skinned Newt, Roughskin Newt, Northern Rough Skin Newt, Crater Lake Newt
© 2006 Kim Cabrera (1 of 143)
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
The isolated 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
Possible reasons for amphibian decline
Habitat modification from deforestation, or logging related activities
This species was featured as News of the Week on 4 July 2022:
The co-evolutionary phenomenon where prey defense and the predator's ability to evade the defense escalate over time through reciprocal natural selection is often called an evolutionary 'arms race'. One textbook example is that of the tetrodotoxin-defended newts (Taricha sp.) and their tetrodotoxin-resistant garter snake predators (Thamnophis sp.). However, recent discoveries that bacteria on Taricha skin can produce tetrodotoxin (TTX) (Vaelli et al. 2020) and that the toxicity of individual newts varies over time (Bucciarelli et al. 2016) complicates the application of an arms-race model to these taxa. In a review of arms races between toxic animals and resistant predators, Bucciarelli et al. (2022) revisit the Taricha-Thamnophis ecosystem and propose a new model incorporating a potential role for skin bacteria and inducible variation in TTX defenses. Their study provides a new perspective that is likely to generate further research and discussion on the widely known newt - garter snake study system. (Written by Rebecca Tarvin)
This species was featured as News of the Week on 2 August 2021:
Most amphibians secrete distasteful or toxic substances from their skin. Several groups wield toxins that can be lethal to other animals, or even to themselves. Animals can evolve resistance to toxins through mutations in proteins that prevent toxins from binding. Although these mutations can provide resistance, they often occur in important regions of a protein, such as those critical to nervous system functions. Thus, a problem arises: how can animals avoid the negative effects of mutations that also provide resistance? A pair of recent studies, one on the toxic salamanders Taricha (Gendreau et al. 2021) and another on frogs of the genus Leptodactylus (Mohammadi et al. 2021), which consume toxic toads, suggest that gene duplication is the key; one gene copy can help animals develop toxin resistance while the other copy maintains a functional nervous system. Both studies also show evidence for a fascinating molecular process known as gene conversion, wherein duplicate copies of one gene retain more similar-than-expected DNA sequences. During homologous recombination, two copies of a genome line up and exchange pieces of DNA; however, when two copies of a gene are near each other in the genome, the wrong genes can line up and exchange genetic material, maintaining genetic similarity between duplicate copies of a gene. In newts, gene conversion appears to have copied resistance-conferring mutations from one gene domain to another. In Leptodactylus frogs, strong natural selection countered the force of gene conversion, resulting in one toxin-resistant gene and one toxin-sensitive gene. How newts and frogs regulate the use of these different gene copies remains unknown and will be an exciting future research topic. (Written by Rebecca Tarvin)
This species was featured as News of the Week on 28 September 2020:
Dangerously poisonous newts (Taricha granulosa), which sequester the toxin tetrodotoxin (TTX), and predatory garter snakes (Thamnophis sirtalis), which can evolve TTX resistance, are engaged in a classic coevolutionary arms race. While generally roughly matched, in western Oregon and Washington other factors are important. While local adaptation dominates, a study (Hague et al. 2020) of geographic variation found that toxin levels are clearly predicted by the phylogeographic population genetic structure of newts and by factors in local environments. Still, predators have higher levels of resistance than the toxins of co-existing newts, suggesting intense selection. What at first seems to be intense arm race coevolution is shown to be a landscape level pattern-- a geographic mosaic of coevolution based on a mixture of often intense natural selection as well as demographic and environmental effects. This study enriches our understanding of this fascinating phenomenon, which is taking place over a large expanse of time and space (Written by David B. Wake).
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 D.C. 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.
Originally submitted by: Meredith J. Mahoney (first posted 2000-07-28)
Distribution by: Michelle S. Koo (updated 2022-07-03)
Comments by: Michelle S. Koo (updated 2022-07-03)
Edited by: M. J. Mahoney, Kevin Gin (12/03), Ann T. Chang, Michelle S. Koo (2022-07-03)
Species Account Citation: AmphibiaWeb 2022 Taricha granulosa: Rough-skinned Newt <https://amphibiaweb.org/species/4288> University of California, Berkeley, CA, USA. Accessed Nov 26, 2022.
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Citation: AmphibiaWeb. 2022. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 26 Nov 2022.
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