| Rough-skinned newt | |
|---|---|
 | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Amphibia |
| Order: | Urodela |
| Family: | Salamandridae |
| Genus: | Taricha |
| Species: | T. granulosa |
| Binomial name | |
| Taricha granulosa (Skilton, 1849) | |
The rough-skinned newt or roughskin newt (Taricha granulosa) is a North American newt known for the strong toxin exuded from its skin.
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. [2] [3] The skin is granular, but males are smooth-skinned during breeding season. They measure 6 to 9 cm (2.4 to 3.5 in) in snout-to-vent length, and 11 to 18 cm (4.3 to 7.1 in) overall. [3] 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. [2] Males can be distinguished from females during breeding season by large swollen vent lobes [3] and cornified toe pads. [2]
Habitats of rough-skinned newts are found throughout the Pacific Northwest. 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 was most likely introduced. [4]
A number of subspecies have been defined based on local variants, but only two subspecies have wider recognition: [2] [5]
It is now believed that the Taricha granulosa mazamae subspecies is no longer valid, as specimens that look similar to T.g.m. have been found in areas of Alaska as well.
Many newts produce toxins from skin glands as a defense against predation, but the toxins of the genus Taricha are particularly potent. An acrid smell radiates from the newt, which acts as a warning for animals to stay away. [6] 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. In 1979, a 29-year-old man from Oregon died after ingesting a rough-skinned newt. [7]
The newt produces a neurotoxin called tetrodotoxin (TTX), which in this species was formerly called "tarichatoxin". It is the same toxin found in pufferfish and a number of other marine animals. [8] This toxin targets voltage-gated sodium channels via binding to distinct but allosterically coupled sites. Because TTX is much larger than a sodium ion, it acts like a cork in a bottle and prevents the flow of sodium. The reverse binding to sodium channels in nerve cells blocks electrical signals necessary for conducting nerve impulses. This inhibition of firing action potentials has the effect of inducing paralysis and death by asphyxiation.
Throughout much of the newt's range, the common garter snake (Thamnophis sirtalis) has been observed to exhibit resistance to the tetrodotoxin produced in the newt's 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. Successful predation of the rough-skinned newt by the common garter snake is made possible by the ability of individuals in a common garter snake population to gauge whether the newt's level of toxin is too high to feed on. T. sirtalis assays toxin levels of the rough-skinned newt and decides whether or not the levels are manageable by partially swallowing the newt, and either swallowing or releasing the newt. [9] 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. [10] 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 the amount of newt 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 because the two species compete in developing adaptations and counter adaptations against each other. This has resulted in the newts producing levels of toxin far in excess of what is needed to kill any other conceivable predator. Some newts secrete enough toxins to kill several adult humans. It appears that in some areas, the common garter snake has surpassed the newt in the evolutionary arms race by developing such a strong resistance to the toxin that the newt is unable to compete with its production of the toxin. [6] There has been phylogenetic evidence that indicates elevated resistance to TTX has originated independently and only in certain species of garter snakes. The resistance has evolved in at least two unrelated species in the genus Thamnophis and at least twice within T. sirtalis. [11]
The toxin, when injected into animals, may not kill resistant animals; however, they are normally slowed down by its toxic effects. In snakes, individuals who showed some resistance tended to move slower after TTX injection, while those with less resistance become paralyzed. [12]
Newts are not immune to their own toxin; they only have a heightened resistance. The toxin in newts consists of a tradeoff. Each time they release the toxin, they inject themselves with a few milligrams. The TTX becomes concentrated in certain parts of the tissue after passing through cell membranes. As a result of tissue exposure to the toxin, newts have evolved a protection mechanism via a single amino acid substitution to the voltage-gated sodium channel normally affected by TTX. Puffer fishes show a similar amino acid sequence that allows them to survive from their own toxin exposure. [8]
Predation on newts by T. sirtalis also shows evidence that tetrodotoxin may serve as protection of eggs by the mother. While TTX is mainly located in the glands of the skin, the rough-skinned newt, as well as some other amphibians also possesses TTX in the ovaries and eggs. The higher the skin toxin levels were in the female, the higher the toxin level found in the egg. This is evidence that high toxin levels of the skin may, in fact, be under indirect selection. Since egg toxin levels would ultimately increase the survivability from predators, such as the garter snake, of the offspring, egg toxin levels may be under direct selection by mates, which is detectable via skin toxin levels. [13]
The rough skinned newt uses a form of chemical based avoidance behavior to avoid being eaten by predators, mainly the common garter snake. The snakes, after swallowing, digesting, and metabolizing a rough-skinned newt, release a chemical signature. This stimulus can be detected by a nearby newt and trigger an avoidant response, which allows them to minimize predation risks. In this way, newts are able to differentiate whether a snake is resistant or sensitive to the toxin in order to avoid being preyed upon. However, newts do not avoid the corpses of a recently digested newt that has been left to decompose. This behavior is unlike salamanders that have been documented in avoiding other injured salamanders. [14]
Parasites include the trematode Halipegus occidualis , the adult form of which may infest the newt's esophagus and the anterior of its stomach. [15]
Tetrodotoxin (TTX) is a potent neurotoxin. Its name derives from Tetraodontiformes, an order that includes pufferfish, porcupinefish, ocean sunfish, and triggerfish; several of these species carry the toxin. Although tetrodotoxin was discovered in these fish, it is found in several other animals. It is also produced by certain infectious or symbiotic bacteria like Pseudoalteromonas, Pseudomonas, and Vibrio as well as other species found in symbiotic relationships with animals and plants.
The Mutillidae are a family of more than 7,000 species of wasps whose wingless females resemble large, hairy ants. Their common name velvet ant refers to their resemblance to an ant, and their dense pile of hair, which most often is bright scarlet or orange, but may also be black, white, silver, or gold. Their bright colors serve as aposematic signals. They are known for their extremely painful stings,, and has resulted in the common name "cow killer" or "cow ant" being applied to the species Dasymutilla occidentalis. However, mutillids are not aggressive and sting only in defense. In addition, the actual toxicity of their venom is much lower than that of honey bees or harvester ants. Unlike true ants, they are solitary, and lack complex social systems.
Salamandridae is a family of salamanders consisting of true salamanders and newts. Salamandrids are distinguished from other salamanders by the lack of rib or costal grooves along the sides of their bodies and by their rough skin. Their skin is very granular because of the number of poison glands. They also lack nasolabial grooves. Most species of Salamandridae have moveable eyelids but lack lacrimal glands.
A xenobiotic is a chemical substance found within an organism that is not naturally produced or expected to be present within the organism. It can also cover substances that are present in much higher concentrations than are usual. Natural compounds can also become xenobiotics if they are taken up by another organism, such as the uptake of natural human hormones by fish found downstream of sewage treatment plant outfalls, or the chemical defenses produced by some organisms as protection against predators. The term xenobiotic is also used to refer to organs transplanted from one species to another.
Garter snake is the common name for small to medium-sized snakes belonging to the genus Thamnophis in the family Colubridae. Native to North and Central America, species in the genus Thamnophis can be found in all of the lower 48 United States, and nearly all of the Canadian provinces south of the Northwest Territories and Nunavut—with the exception of Newfoundland and Labrador. They are found from the subarctic plains of west-central Canada east through Ontario and Quebec; from the Maritime Provinces and south to Florida, across the southern and central U.S. into the arid regions of the southwest and Mexico, Guatemala and south to the neotropics and Costa Rica.
The common garter snake is a species of snake in the subfamily Natricinae of the family Colubridae. The species is indigenous to North America and found widely across the continent. There are several recognized subspecies. Most common garter snakes have a pattern of yellow stripes on a black, brown or green background, and their average total length is about 55 cm (22 in), with a maximum total length of about 137 cm (54 in). The average body mass is 150 g (5.3 oz). The common garter snake is the state reptile of Massachusetts.
In evolutionary biology, an evolutionary arms race is an ongoing struggle between competing sets of co-evolving genes, phenotypic and behavioral traits that develop escalating adaptations and counter-adaptations against each other, resembling the geopolitical concept of an arms race. These are often described as examples of positive feedback. The co-evolving gene sets may be in different species, as in an evolutionary arms race between a predator species and its prey, or a parasite and its host. Alternatively, the arms race may be between members of the same species, as in the manipulation/sales resistance model of communication or as in runaway evolution or Red Queen effects. One example of an evolutionary arms race is in sexual conflict between the sexes, often described with the term Fisherian runaway. Thierry Lodé emphasized the role of such antagonistic interactions in evolution leading to character displacements and antagonistic coevolution.
The Chinese fire belly newt is a small black newt, with bright-orange aposematic coloration on their ventral sides. C. orientalis is commonly seen in pet stores, where it is frequently confused with the Japanese fire belly newt due to similarities in size and coloration. C. orientalis typically exhibits smoother skin and a rounder tail than C. pyrrhogaster, and has less obvious parotoid glands. C. orientalis is native to subtropical forests in China and prefers to live in shallow, semiaquatic environments such as abandoned paddies and ponds with dense vegetation.
The Siskiyou Mountains salamander, also called the Siskiyou Mountain salamander, exists only in isolated locations along the Klamath River in northern California and southern Oregon. It is a close relative of the Del Norte salamander, and some herpetologists believe it may be a subspecies of that animal.
The genus Taricha consists of four species of highly toxic newts in the family Salamandridae. Their common name is Pacific newts, sometimes also western newts or roughskin newts. The four species within this genus are the California newt, the rough-skinned newt, the red-bellied newt, and the sierra newt, all of which are found on the Pacific coastal region from southern Alaska to southern California, with one species possibly ranging into northern Baja California, Mexico.
The California newt or orange-bellied newt, is a species of newt endemic to California, in the Western United States. Its adult length can range from 5 to 8 in. Its skin produces the potent toxin tetrodotoxin.
The greater blue-ringed octopus is one of four species of extremely venomous blue-ringed octopuses belonging to the family Octopodidae. This particular species of blue-ringed octopus is known as one of the most toxic marine animals in the world.
The San Francisco garter snake is a slender multi-colored subspecies of the common garter snake. Designated as an endangered subspecies since the year 1967, it is endemic to San Mateo County and the extreme northern part of coastal Santa Cruz County in California.
The Sierra newt is a newt found west of the Sierra Nevada, from Shasta county to Tulare County, in California, Western North America.
Atelopus oxyrhynchus is a species of toad in the family Bufonidae. It is endemic to Venezuela. Its natural habitats are subtropical or tropical moist montane forests, rivers, and intermittent rivers. It is threatened by habitat loss.
A newt is a salamander in the subfamily Pleurodelinae. The terrestrial juvenile phase is called an eft. Unlike other members of the family Salamandridae, newts are semiaquatic, alternating between aquatic and terrestrial habitats. Not all aquatic salamanders are considered newts, however. More than 100 known species of newts are found in North America, Europe, North Africa and Asia. Newts metamorphose through three distinct developmental life stages: aquatic larva, terrestrial juvenile (eft), and adult. Adult newts have lizard-like bodies and return to the water every year to breed, otherwise living in humid, cover-rich land habitats.
The Coastal Range newt is a subspecies of the California newt. It is endemic to California, from Mendocino County south to San Diego County.
Poisonous amphibians are amphibians that produce toxins to defend themselves from predators.
There are 14 species of amphibians and 5 species of reptiles known to occur in Mount Rainier National Park.
Data related to Taricha granulosa at Wikispecies 
Media related to Taricha granulosa at Wikimedia Commons
