Gourt Home::Gourt :: Newt
This article is about the animal called newt. For other meanings, see Newt (disambiguation).
Newts are small, usually bright-coloured semiaquatic salamanders of North America, Europe and North Asia, distinguished from other salamanders by the lack of rib or costal grooves along the sides of the body.
Newts have the ability to regenerate limbs, eyes and spinal cords. The cells at the site of the injury have the ability to de-differentiate, reproduce rapidly, and differentiate again to create a new limb or organ. One theory is that the de-differentiated cells are related to tumour cells since chemicals which produce tumours in other animals will produce additional limbs in newts.
Many newts produce toxins in their skin secretions as a defence mechanism against predators. The Taricha newts of western North America are particularly toxic; the Rough-skinned Newt (Taricha granulosa) of the Pacific Northwest produces more than enough tetrodotoxin to kill an adult human foolish enough to swallow a newt. Note that in order to produce harm, the toxins have to enter the body by being ingested or entering a break in the skin; it is safe to handle newts provided one thoroughly washes ones hands before eating.
Newts can take several years to reach sexual maturity. It is known that their main breeding season is between February and June. They are hatched as tadpoles from eggs laid in ponds or slow-moving streams (see image below) and then undergo metamorphosis, during which time they commonly leave the water, only to return to the water to live out their adult lives. During the time right after metamorphosis, many North American Newt species go through a phase called the eft phase. Their skin turns a reddish color and the animal lives its life on land, almost never seen in the water. It is not until the eft reaches adulthood will it begin to live its life in a more aquatic fashion, during which time it may rarely venture onto land.
Distribution
The three common British species are the Great Crested Newt (Triturus cristatus), Smooth Newt (Triturus vulgaris) and the Palmate Newt (Triturus helveticus). On the mainland of Europe exists such species as the Spanish Ribbed Newt (Plurodeles waltl), the largest species of newt, the Alpine Newt, and the Southern Crested Newt.
In North America, the Red-spotted Newt (Notophthalmus viridescens) is one of the most abundant species, but it is limited to the area east of the Rocky Mountains so it is also called the "Eastern Newt". The three species of Coastal newt are the Red Bellied Newt, the California Newt, and the Rough-skinned Newt, all of which belong to the genus Taricha, which is confined to the area west of the Rockies.
In Japan, the Sword-tail Newt (Cynops ensicauda) is becoming rare and is threatened by pollution and deforestation.
Etymology
The history of the word newt is interesting. The oldest form of the name is eft, which is still used for newly metamorphosed juveniles, but according to the Oxford English Dictionary it changed for unknown reasons first to euft and then to ewt. For some time it remained as an ewt, but the N from the indefinite article an shifted to form a newt. See A, an for other examples.
External references
Тритон | Madfall ddŵr | Molch (Biologie) | Salamandra salamandra | Tritone (anfibi) | イモリ | newt
"Newt"