The
rough-skinned newt is a
North AmericaNorth America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
n
newtA newt is an aquatic amphibian of the family Salamandridae, although not all aquatic salamanders are considered newts. Newts are classified in the subfamily Pleurodelinae of the family Salamandridae, and are found in North America, Europe and Asia...
known for its strong poison.
Toxicity
Many newts produce toxins to avoid
predationIn ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
, but the toxins of the genus
TarichaThe genus Taricha consists of three species and four subspecies of Western Newts . All newts are part of the family Salamandridae...
are particularly potent. Toxicity is generally experienced only if the newt is ingested, although there are reports that some individuals experience skin irritation after dermal contact.
Toxin
The rough-skinned newt possesses
tetrodotoxinTetrodotoxin, also known as "tetrodox" and frequently abbreviated as TTX, sometimes colloquially referred to as "zombie powder" by those who practice Vodou, is a potent neurotoxin with no known antidote. There have been successful tests of a possible antidote in mice, but further tests must be...
, which in this species was formerly called
tarichatoxin. 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 snakeThe Common Garter Snake is a snake indigenous to North America. Most garter snakes have a pattern of yellow stripes on a brown or green background and their average length is about , maximum about .-Subspecies:...
(
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 T. granulosa newt and survive.
In evolutionary theory, the relationship between the rough-skinned newt and the common garter snake is considered an example of
co-evolutionIn biology, coevolution is "the change of a biological object triggered by the change of a related object." Coevolution can occur at many biological levels: it can be as microscopic as correlated mutations between amino acids in a protein, or as macroscopic as covarying traits between different...
. 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 raceIn evolutionary biology, an evolutionary arms race is an evolutionary struggle between competing sets of co-evolving genes that develop adaptations and counter-adaptations against each other, resembling an arms race, which are also examples of positive feedback...
and has resulted in the newts producing levels of toxin far in excess of what is needed to kill any other conceivable predator.
Distribution
HabitatsA habitat is an ecological or environmental area that is inhabited by a particular species of animal, plant or other type of organism...
of rough-skinned newts are found throughout the
West Coast of the United StatesWest Coast or Pacific Coast are terms for the westernmost coastal states of the United States. The term most often refers to the states of California, Oregon, and Washington. Although not part of the contiguous United States, Alaska and Hawaii do border the Pacific Ocean but can't be included in...
and
British ColumbiaBritish Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
. Their range extends south to
Santa CruzSanta Cruz is the county seat and largest city of Santa Cruz County, California in the US. As of the 2010 U.S. Census, Santa Cruz had a total population of 59,946...
,
CaliforniaCalifornia is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
and north to
AlaskaAlaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
. They are uncommon east of the Cascade Mountains though occasionally found (and considered exotic, and possibly artificially introduced) as far as Montana. One isolated population lives in several ponds just north of
Moscow, IdahoMoscow is a city in northern Idaho, situated along the Washington/Idaho border. It is the most populous city and county seat of Latah County and the home of the University of Idaho, the land grant institution and primary research university for the state...
and were most likely introduced.
Parasites
Parasites include the trematode
Helipegus occidualis, the adult form of which may infest the newt's esophagus and the anterior of their stomach.
See also
- Cosmocercoides
Cosmocercoides is a genus of nematode within the order Ascaridida. Nematodes within the genus Cosmocercoides have been found as parasites within the rough-skinned newt, Taricha granulosa...
- Salamander
Salamander is a common name of approximately 500 species of amphibians. They are typically characterized by a superficially lizard-like appearance, with their slender bodies, short noses, and long tails. All known fossils and extinct species fall under the order Caudata, while sometimes the extant...
- California Newt
The California newt is a newt. It is also referred to as the orange bellied newt. They can grow to be in length.- Physical description :T. torosa adult length can range from to...
- Red Bellied Newt
- Salamandridae
Salamandridae is a family of salamanders consisting of true salamanders and newts. Currently, 74 species have been identified in the northern hemisphere - Europe, Asia, the northern tip of Africa and North America...