A newt is an aquatic amphibian of the family Salamandridae, although not all aquatic salamanders
are considered newts.
Newts are classified in the salamandrid subfamily Pleurodelinae, and are found in North America,
Europe and Asia.
Newts metamorphose through three distinct developmental life stages: aquatic larva,
terrestrial juvenile, and adult.
Adult newts have lizard-like bodies and may be either fully aquatic, living permanently
in the water, or semi-aquatic, living terrestrially but returning to the water each year to breed.
Names The Old English name of the animal was efte,
efeta, resulting in Middle English eft; this word was transformed irregularly into euft,
evete ewt(e).
The initial n was added from the indefinite article an by provection by the early 15th
century.
The form newt appears to have arisen as a dialectal variant of eft in Derbyshire and
Staffordshire, but entered Standard English by the Early Modern period.
The regular form eft, now only used for newly metamorphosed specimens, survived alongside
newt, especially in composition, the larva being called "water-eft" and the mature form
"land-eft" well into the 18th century, but use of the simplex "eft" as equivalent to
"water-eft" has been in use since at least the 17th century.
Dialectal English and Scots also has the word ask used for both newts and wall lizards,
from Old English āþexe, from Proto-Germanic *agiþahsijǭ literally "lizard-badger".
Latin had the name stellio for a type of spotted newt, now used for species of the Stellagama
genus.
Ancient Greek had the name κορδύλος, presumably for the water newt.
German has Molch, from Middle High German mol, olm, like the English term of unknown
etymology.
Newts are also known as Tritones in historical literature, and "triton" remains in use as
common name in some Romance languages, in Greek and in Russian.
The systematic name Tritones was introduced alongside Pleurodelinae by Tschudi in 1838,
based on the type genus named Triton by Laurenti in 1768.
Laurenti's Triton was renamed to Triturus by Rafinesque in 1815.
Tschudi's Pleurodelinae is based on the type genus Pleurodeles named by Michahelles in
1830.
Characteristics
Newts share many of the characteristics of their salamander kin, Caudata, including semi-permeable
glandular skin, four equal-sized limbs and a distinct tail.
The newt's skin, however, is not as smooth as that of other salamanders.
Aquatic larvae have true teeth on both upper and lower jaws, and external gills.
They have the ability to regenerate limbs, eyes, spinal cords, hearts, intestines, and
upper and lower jaws.
The Japanese fire belly newt can regenerate its eye lens 18 times over a period of 16
years and retain its structural and functional properties.
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.
Development
The main breeding season for newts is between the months of June and July.
After courtship rituals of varying complexity, which take place in ponds or slow moving streams,
the male newt transfers a spermatophore which is taken up by the female.
Fertilized eggs are laid singly and are usually attached to aquatic plants.
This distinguishes them from the free-floating eggs of frogs or toads, that are laid in clumps
or in strings.
Plant leaves are usually folded over and adhered to the eggs to protect them.
The tadpoles, which resemble fish fry but are distinguished by their feathery external
gills, hatch out in about three weeks.
After hatching they eat algae, small invertebrates or other tadpoles.
During the next few months the tadpoles undergo metamorphosis, during which they develop legs,
and the gills are absorbed and replaced by air-breathing lungs.
Some species, such as the North American newts, also become more brightly coloured during
this phase.
Once fully metamorphosised they leave the water and live a terrestrial life, when they
are known as "efts".
Only when the eft reaches adulthood will the North American species return to live in water,
rarely venturing back onto the land.
Conversely, most European species live their adult lives on land and only visit water to
breed.
Toxicity Many newts produce toxins in their skin secretions
as a defence mechanism against predators.
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, and some Native Americans of the Pacific Northwest
used the toxin to poison their enemies.
However, the toxins are only dangerous if ingested, and the newts can easily and safely
live in the same ponds or streams as frogs and other amphibians, or be safely kept as
pets.
The only predators of Taricha newts are garter snakes, some having developed a resistance
to the poison.
Most newts can be safely handled, provided that the toxins they produce are not ingested
or allowed to come in contact with mucous membranes, or breaks in the skin.
After handling, proper hand-washing techniques should be followed due to the risk from the
toxins they produce and bacteria they carry, such as salmonella.
It is, however, illegal to handle or disturb great crested newts in the UK without a licence.
As bioindicators Newts, as with salamanders in general, serve
as bioindicators because of their thin, sensitive skin and evidence of their presence can serve
as an indicator of the health of the environment.
Most species are highly sensitive to subtle changes in the pH level of streams and lakes
they live in.
Because their skin is permeable to water they absorb oxygen and other substances they need
through their skin.
Scientists will study the stability of the amphibian population when studying the water
quality of a particular body of water.
Systematics About two thirds of all species of the family
Salamandridae, comprising the following genera, are commonly called "newts":
The term "newt" has traditionally been seen as an exclusively functional term for salamanders
living in water, and not a systematic unit.
The relationship between the genera has been uncertain, although it has been suggested
that they constitute a natural systematic unit and newer molecular analyses tend to
support this position.
Newts only appear in one subfamily of salamanders, the Pleurodelinae, however, Salamandrina and
Euproctus, which are sometimes listed as Pleurodelinae, are not newts.
Whether these are basal to the subfamily or derived, making the newts an evolutionary
grade is currently not known.
Distribution The three common European genera are the crested
newts, the smooth and palmate newts and the banded newts.
Other species present in Europe are the Iberian ribbed newt, which is the largest of the European
newts, the Pyrenean brook newt; the European brook newt and the alpine newt.
In North America, there are the eastern newts, of which the red-spotted newt is the most
abundant species, but it is limited to the area east of the Rocky Mountains.
The three species of coastal or western newts 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 Southeast Asia and Japan, species commonly encountered in the pet trade include the fire
belly newts, the paddletail newts, the crocodile newts, and the warty newts.
In the Middle East there are the spotted newts.
Conservation status Yunnan lake newt is considered extinct.
Europe Some newt populations in Europe have decreased
because of pollution or destruction of their breeding sites and terrestrial habitats, and
countries such as the UK have taken steps to halt their declines.
In the UK, they are protected under the Wildlife and Countryside Act 1981 and the Habitat Regulations
Act 1994.
It is illegal to catch, possess or handle Great crested newts without a licence, and
it is also illegal to cause them harm or death, or to disturb their habitat in any way.
The IUCN Red List categorises the species as ‘lower risk’ Although the other UK
species, the Smooth newt and Palmate newt are not listed, the sale of either species
is prohibited under the Wildlife and Countryside Act, 1981.
In Europe, nine newts are listed as "strictly protected fauna species" under appendix II
of the Convention on the Conservation of European Wildlife and Natural Habitats:
The remaining European species are listed as "protected fauna species" under appendix
III.
In literature A newt plays a key role in Roald Dahl's children's
book Matilda when, in the chapter 'The First Miracle', Matilda's friend Lavender slips
a newt into the headmistress Miss Trunchbull's water.
The eponymous heroine Matilda Wormwood later tips it over by telekinesis.
References
External links Data related to Pleurodelinae at Wikispecies