Rough-skinned newt
| Rough-skinned newt | |
|---|---|
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| Conservation status | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Amphibia |
| Order: | Caudata |
| Family: | Salamandridae |
| Genus: | Taricha |
| Species: | T. granulosa |
| Binomial name | |
| Taricha granulosa |
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The rough-skinned newt (Taricha granulosa) is a North American newt known for its strong toxin exuded from its skin.
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Appearance
A stocky newt with rounded snout, it ranges from light brown to olive or brownish-black on top, with the underside, including the head, legs, and tail, a contrasting orange to yellow.[1][2] The skin is granular, but males are smooth-skinned during breeding season. They measure 6 to 9 cm in snout-to-vent length, and 11 to 18 cm overall.[2] They are similar to the California newt (Taricha torosa) but differ in having smaller eyes, yellow irises, V-shaped tooth patterns, and uniformly dark eyelids.[1] Males can be distinguished from females during breeding season by large swollen vent lobes[2] and cornified toe pads.[1]
Distribution
Habitats of rough-skinned newts are found throughout the West Coast of the United States and British Columbia. Their range extends south to Santa Cruz, California, and north to Alaska. They are uncommon east of the Cascade Mountains, though occasionally are found (and considered exotic, and possibly artificially introduced) as far as Montana. One isolated population lives in several ponds just north of Moscow, Idaho, and were most likely introduced.[3]
Toxicity
Many newts produce toxins from skin glands as a defence against predation, but the toxins of the genus Taricha are particularly potent. Toxicity is generally experienced only if the newt is ingested, although some individuals have been reported to experience skin irritation after dermal contact, particularly if the eyes are touched after handling the animal without washing hands. On a dare, a 29-year-old man in Oregon swallowed a 20-cm rough-skinned newt and died.[4]
Toxin
The newt's toxin is a neurotoxin called tetrodotoxin, which in this species was formerly called "tarichatoxin". It is the same toxin found in pufferfish and a number of other marine animals. This toxin binds reversibly to sodium channels in nerve cells and interferes with the normal flow of sodium ions in and out of the cell. This has the effect of inducing paralysis and death.
Toxin resistance and predation
Throughout much of the newt’s range, the common garter snake (Thamnophis sirtalis) has been observed to exhibit resistance to the tetrodotoxin produced in its skin. While in principle the toxin binds to a tube-shaped protein that acts as a sodium channel in the snake's nerve cells, researchers have identified a genetic disposition in several snake populations where the protein is configured in such a way as to hamper or prevent binding of the toxin. In each of these populations, the snakes exhibit resistance to the toxin and successfully prey upon the newts. Toxin-resistant garter snakes are the only known animals today that can eat a rough-skinned newt and survive.
In evolutionary theory, the relationship between the rough-skinned newt and the common garter snake is considered an example of co-evolution.[5] The mutations in the snake’s genes that conferred resistance to the toxin have resulted in a selective pressure that favors newts which produce more potent levels of toxin. Increases in newt toxicity then apply a selective pressure favoring snakes with mutations conferring even greater resistance. This cycle of a predator and prey evolving to one another is sometimes termed an evolutionary arms race and has resulted in the newts producing levels of toxin far in excess of what is needed to kill any other conceivable predator.
Parasites
Parasites include the trematode Helipegus occidualis, the adult form of which may infest the newt's esophagus and the anterior of its stomach.[6]
See also
Line notes
- ^ a b c Nelson, Nate (2003). "Taricha granulosa". Caudata Culture website. Retrieved February 28, 2013.
- ^ a b c Hallock, L. A. (2005). "Rough-skinned newt". Washington Herp Atlas. Dept. of Natural Resources, Washington State. Retrieved February 28, 2013.
- ^ Natureserve Explorer
- ^ Bradley, Susan G.; Klika, Larry J. (July 1981). "A fatal poisoning from the Oregon rough-skinned newt (Taricha granulosa)". JAMA : The Journal of the American Medical Association 246 (3): 247. doi:10.1001/jama.1981.03320030039026. PMID 7241765.
- ^ American Book Company, Liz Thompson (2006). Passing the New Jersey High School Proficiency Assessment in Science. American Book Company. p. 106. ISBN 1-59807-103-3 [Amazon-US | Amazon-UK].
- ^ Marvin Clinton Meyer, Oliver Wilford Olsen (1975). Essentials of parasitology (2, illustrated ed.). W. C. Brown Co. p. 79. ISBN 0-697-04682-6, 9780697046826 Check
|isbn=value (help).
References
- Hammerson (2004). Taricha granulosa. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 12 May 2006.
- "Taricha granulosa: Rough-skinned Newt". Caudata Culture. Retrieved 2006-07-26.
- Geffeney, Shana L., et al. “Evolutionary diversification of TTX-resistant sodium channels in a predatorÂ-prey interaction”. Nature 434 (2005): 759–763.
- "Taricha granulosa granulosa – Rough-Skinned Newt". California Herps. Retrieved 2006-12-10.
- C. Michael Hogan (2008) Rough-skinned Newt (Taricha granulosa), Globaltwitcher, ed. N. Stromberg [1]
External links
Data related to Taricha granulosa at Wikispecies 
Media related to Taricha granulosa at Wikimedia Commons