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A newt is a
salamander Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All t ...
in the
subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus Genus ( plural genera ) is a taxonomic rank used in the biological classifica ...
Pleurodelinae. The terrestrial juvenile phase is called an eft. Unlike other members of the family
Salamandridae 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 ...
, 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 A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. ...
, terrestrial juvenile (eft), and adult. Adult newts have
lizard Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia altho ...
-like bodies and return to the water every year to breed, otherwise living in humid, cover-rich land habitats. Newts are threatened by
habitat loss Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...
, fragmentation and
pollution Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, th ...
. Several species are endangered, and at least one species, the Yunnan lake newt, has become
extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
recently.


Etymology

The
Old English Old English (, ), or Anglo-Saxon, is the earliest recorded form of the English language, spoken in England and southern and eastern Scotland in the early Middle Ages. It was brought to Great Britain by Anglo-Saxon settlers in the mid-5th ...
name of the animal was , (of unknown origin), resulting in
Middle English Middle English (abbreviated to ME) is a form of the English language that was spoken after the Norman conquest of 1066, until the late 15th century. The English language underwent distinct variations and developments following the Old Englis ...
; this word was transformed irregularly into , , or . The initial "n" was added from the indefinite article "an" by provection (juncture loss) ("an eft" → "a n'eft" → ...) by the early 15th century. The form "newt" appears to have arisen as a dialectal variant of ''eft'' in
Staffordshire Staffordshire (; postal abbreviation Staffs.) is a landlocked county in the West Midlands region of England. It borders Cheshire to the northwest, Derbyshire and Leicestershire to the east, Warwickshire to the southeast, the West Midlands C ...
, but entered Standard English by the Early Modern period (used by Shakespeare in ''
Macbeth ''Macbeth'' (, full title ''The Tragedie of Macbeth'') is a tragedy by William Shakespeare. It is thought to have been first performed in 1606. It dramatises the damaging physical and psychological effects of political ambition on those w ...
'' iv.1). 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 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'' (also ''awsk'', ''esk'' in Scots) used for both newts and wall lizards, from Old English '' āþexe'', from
Proto-Germanic Proto-Germanic (abbreviated PGmc; also called Common Germanic) is the reconstructed proto-language of the Germanic branch of the Indo-European languages. Proto-Germanic eventually developed from pre-Proto-Germanic into three Germanic br ...
'' *agiþahsijǭ'', literally "lizard-badger" or "distaff-like lizard" (compare German '' Eidechse'' and '' Echse'', both "lizard;" ''*agi-'' is ultimately cognate with Greek "snake," from
Proto-Indo-European Proto-Indo-European (PIE) is the reconstructed common ancestor of the Indo-European language family. Its proposed features have been derived by linguistic reconstruction from documented Indo-European languages. No direct record of Proto-Indo ...
'' *h₁ogʷʰis''). Latin had the name ''stellio'' for a type of spotted newt, now used for species of the genus ''
Stellagama ''Laudakia stellio '' is a species of agamid lizard.Baig KJ et al. (2012)"A morphology-based taxonomic revision of ''Laudakia'' Gray, 1845 (Squamata: Agamidae)".''Vertebrate Zoology'' 62 (2): 213–260. (''Stellagama'', new genus, p. 222). also ...
''. Ancient Greek had the name , presumably for the water newt (immature newt, eft). German has , from
Middle High German Middle High German (MHG; german: Mittelhochdeutsch (Mhd.)) is the term for the form of German spoken in the High Middle Ages. It is conventionally dated between 1050 and 1350, developing from Old High German and into Early New High German. Hig ...
''mol'', '' :wikt:olm'', like the English term of unknown etymology. Newts are also known as ''Tritones'' (viz., named for the mythological
Triton Triton commonly refers to: * Triton (mythology), a Greek god * Triton (moon), a satellite of Neptune Triton may also refer to: Biology * Triton cockatoo, a parrot * Triton (gastropod), a group of sea snails * ''Triton'', a synonym of ''Triturus'' ...
) in historical literature, and "triton" remains in use as common name in some Romance languages, in Greek, in Romanian, Russian, and Bulgarian. 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'' ("Triton-tail") by Rafinesque in 1815. Tschudi's Pleurodelinae is based on the type genus '' Pleurodeles'' (ribbed newt) named by Michahelles in 1830 (the name meaning "having prominent ribs," formed from "ribs" and "conspicuous").


Distribution and habitats

Newts are found in North America, Europe, North Africa and Asia. The Pacific newts (''Taricha'') and the Eastern newts (''Notophthalmus'') with together seven species are the only representatives in North America, while most diversity is found in the Old World: In Europe and the Middle East, the group's likely origin, eight genera with roughly 30 species are found, with the ribbed newts (''Pleurodeles'') extending to northernmost Africa. Eastern Asia, from Eastern India over Indochina to Japan, is home to five genera with more than 40 species. Newts are semiaquatic, spending part of the year in the water for reproduction and the rest of the year on land. While most species prefer stagnant water bodies such as ponds, ditches, or flooded meadows for reproduction, some species such as the
Danube crested newt The Danube crested newt or Danube newt (''Triturus dobrogicus'') is a species of newt found in central and eastern Europe, along the basin of the Danube river and some of its tributaries and in the Dnieper delta. It has a smaller and more slender ...
can also occur in slow-flowing rivers. The European brook newts (''Calotriton'') and European mountain newts (''Euproctus'') have even adapted to life in cold, oxygen-rich mountain streams. During their terrestrial phase, newts live in humid habitats with abundant cover such as logs, rocks, or earth holes.


Characteristics

Newts share many of the characteristics of their salamander kin, Caudata, including semipermeable glandular skin, four equal-sized limbs, and a distinct tail. The newt's skin, however, is not as smooth as that of other salamanders. The cells at the site of an injury have the ability to un differentiate, reproduce rapidly, and differentiate again to create a new limb or organ. One hypothesis is that the undifferentiated cells are related to
tumor A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...
cells, since chemicals that produce tumors in other animals will produce additional limbs in newts.


Development

The main breeding season for newts (in the Northern Hemisphere) is in June and July. A single newt female can produce hundreds of eggs. For instance, the warty newt can produce 200–300 eggs (Bradford 2017). After courtship rituals of varying complexity, which take place in ponds or slow-moving streams, the male newt transfers a
spermatophore A spermatophore or sperm ampulla is a capsule or mass containing spermatozoa created by males of various animal species, especially salamanders and arthropods, and transferred in entirety to the female's ovipore during reproduction. 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
frog A frog is any member of a diverse and largely Carnivore, carnivorous group of short-bodied, tailless amphibians composing the order (biology), order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-f ...
s or
toad Toad is a common name for certain frogs, especially of the family Bufonidae, that are characterized by dry, leathery skin, short legs, and large bumps covering the parotoid glands. A distinction between frogs and toads is not made in scient ...
s, which are laid in clumps or in strings. Plant leaves are usually folded over and attached to the eggs to protect them. The
larvae A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. T ...
, 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 amphibian larvae. During the subsequent few months, the larvae undergo
metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some inse ...
, 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 colored during this phase. Once fully metamorphosed, 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
toxin A toxin is a naturally occurring organic poison produced by metabolic activities of living cells or organisms. Toxins occur especially as a protein or conjugated protein. The term toxin was first used by organic chemist Ludwig Brieger (1849 ...
s in their skin secretions as a defence mechanism against predators. ''Taricha'' newts of western North America are particularly toxic. The
rough-skinned newt The rough-skinned newt or roughskin newt (''Taricha granulosa'') is a North American newt known for the strong toxin exuded from its skin. Appearance A stocky newt with rounded snout, it ranges from light brown to olive or brownish-black on ...
''Taricha granulosa'' of the
Pacific Northwest The Pacific Northwest (sometimes Cascadia, or simply abbreviated as PNW) is a geographic region in western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Thou ...
produces more than enough
tetrodotoxin 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 discovere ...
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 or otherwise enter the body; for example, through a wound. Newts can safely live in the same ponds or streams as frogs and other amphibians or be kept as pets. The only predators of ''Taricha'' newts are garter snakes, some having developed a resistance to the toxin. Most newts can be safely handled, provided the toxins they produce are not ingested or allowed to come in contact with
mucous membrane A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It i ...
s or breaks in the skin.


Systematics

Newts form one of three subfamilies in the family
Salamandridae 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 ...
, aside Salamandrinae and
Salamandrininae ''Salamandrina'', the spectacled salamanders, is a genus of salamander, the only of subfamily Salamandrininae in the family Salamandridae which is still alive, as one of its own relatives is extinct. The IUCN Red List follows Mattoccia et al. (20 ...
. They comprise most
extant Extant is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Extant taxon, a taxon which is not extinct, ...
species in the family, roughly 100, which are classified in sixteen genera: * ''
Calotriton ''Calotriton'', or the European brook newts, is a genus of newts native to the Pyrenees and central Catalonia (Catalan Pre-coastal Range). These amphibians were formerly placed within genus ''Euproctus'', but the genus was resurrected in 2005. ...
'' * ''
Cynops The fire belly newt or fire newt is a genus (''Cynops'') of newts native to Japan and China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by pop ...
'' (incl. ''Hypselotriton'') * '' Echinotriton'' * ''
Euproctus ''Euproctus'', the European mountain salamanders, is a genus of salamanders in the family Salamandridae from Sardinia and Corsica Corsica ( , Upper , Southern ; it, Corsica; ; french: Corse ; lij, Còrsega; sc, Còssiga) is an island in t ...
'' * '' Ichthyosaura'' * ''
Laotriton The Laos warty newt (''Laotriton laoensis'') is a species of salamander in the family Salamandridae. It is found only in the Saysomboun Special Zone and Phou Kout District in Xiangkhouang Province, Laos. Its natural habitats are subtropical or ...
'' * ''
Lissotriton ''Lissotriton'' is a genus of newts native to Europe and parts of Asia Minor. As most other newts, they are aquatic as larvae and during breeding time but live in terrestrial, humid environments over the rest of the season. These rather small sp ...
'' * ''
Neurergus ''Neurergus'' is a genus of salamanders, more specifically newts, in the family Salamandridae. They are found in the Middle East (predominantly in Turkey and Iran), and are kept and bred in captivity for their bright colors. In nature, they inha ...
'' * ''
Notophthalmus ''Notophthalmus'' is a genus of newt 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 aqua ...
'' * ''
Ommatotriton ''Ommatotriton'' or ''banded newts'' is a genus of salamanders in the family Salamandridae. The genus occurs in Western Asia and Caucasus The Caucasus () or Caucasia (), is a region between the Black Sea and the Caspian Sea, mainly compris ...
'' * ''
Pachytriton ''Pachytriton'', also known as the paddle-tail newts or Chinese newts, is a genus of salamanders in the family Salamandridae Salamandridae is a family of salamanders consisting of true salamanders and newts. Salamandrids are distinguished fr ...
'' * ''
Paramesotriton ''Paramesotriton'', also known as warty newts or Asian warty newts, is a genus of salamanders in the family Salamandridae. The genus is found in southwestern and southern China and in northern Vietnam. Most of the species are endemic to China, a ...
'' * '' Pleurodeles'' * ''
Taricha 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, ...
'' * '' Triturus'' * ''
Tylototriton ''Tylototriton'' is a genus of newt 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 ...
'' (incl. ''Liangshantriton'') ''Hypselotriton'' and ''Liangshantriton'' are regarded as separate genera by some authors, but this is not unanimous. The term "newt" has traditionally been seen as an exclusively functional term for salamanders living in water, and not a
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...
.
Phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups ...
analyses have however shown that species in the Salamandridae traditionally called newts do form a
monophyletic group A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...
. Other, more distantly related salamander families also contain fully or in part aquatic species, such as the mole salamanders, the Proteidae, or the Sirenidae. Classification of all genera of the Pleurodelinae subfamily after Pyron and Weins, revised by Mikko Haaramo.


Phylogenetics

Phylogenetic analyses estimated the origin of the newt subfamily in the
Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', ...
to
Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', ...
. Several fossil salamanders have also been referred to the Pleurodelinae, including: * '' Archaeotriton'' * '' Brachycormus'' * ''
Carpathotriton 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 aquat ...
'' * '' Chelotriton'' * '' Koalliella'' * '' Palaeopleurodeles''


Anatomy and physiology


Circulation

The heart of newts, like that of most amphibians, consists of two atria and one ventricle.(Miyachi, Y. 2011. The Unusual Circulation of the Newt Heart after Ventricular Injury and Its Implications for Regeneration. Anatomy Research International:1-7). Blood flows from the anterior and posterior caval veins into the right atrium; blood that entered the heart from the left atrium is then expelled out of the ventricle. Newts do not have a
coronary artery The coronary arteries are the arterial blood vessels of coronary circulation, which transport oxygenated blood to the heart muscle. The heart requires a continuous supply of oxygen to function and survive, much like any other tissue or organ o ...
on the ventricle, due to circulation that is found in the conus arteriosus. Newts contain a special circulatory adaptation that allows them to survive ventricular penetration: when a newt's ventricle is punctured, the heart will divert the blood directly into an ascending aorta via a duct located between the ventricle and the conus arteriosus. Newts begin to regenerate the ventricle by a thickening of the
epicardial The pericardium, also called pericardial sac, is a double-walled sac containing the heart and the roots of the great vessels. It has two layers, an outer layer made of strong connective tissue (fibrous pericardium), and an inner layer made o ...
layer that protrudes to allow the new vessels to form, and conclude with a regeneration of the entire myocardial wall. In early stages of development in amphibians, ventilator gas transport and hemoglobin gas transport are independent mechanisms and not yet coupled as they are in adulthood.(Pelster, B. 1999. Environmental Influences on the Development of the Cardiac System in Fish and Amphibians. Comparative Biochemistry and Physiology Part A 124:407-412) In juvenile amphibians, there is no cardiovascular response in conditions of hypoxia. When newts are induced into anemia, they are able to respire without the need of blood cells.(Casale. G.P, Khairallah. E. A., Grasso. J. A. 1980. An Analysis of Hemoglobin Synthesis in Erythropoietic Cells. Developmental Biology 80:107-119. ) In ''T. carnifex'', around two weeks after anemia is induced, the newts produced a mass of cells that helps to revitalize the already circulating red blood cell mass.


Respiration

Adult crested newts (''Triturus cristus'') were found to breathe mainly via the skin but also through the lungs and the buccal cavity. Lung breathing is mainly used when there is a lack of oxygen in the water, or at high activity such as during courtship, breeding, or feeding.(Eddy, F. B., P. McDonald. 1978. Aquatic respiration of The Crested Newt Triturus Cristatus. Comparative Biochemical Physiology. 59: 85-88) A form of compensatory respiration is the ability to release stored erythrocytes when needed, for example under hypoxia.(Giuliano Frangioni, Mario Santoni, Stefano Bianchi, Marco Franchi, Giancarlo Fuzzi, Stefano Marcaccini, Carlo Varlani, Gianfranco Borgioli. 2006. Function of the Hepatic Melanogenesis in the Newt, Triturus Carnifex. Journal of Experimental Zoology. 303A:123-131.)(Frangioni, G., G. Borgioli. 1996. Variations in blood pressure of newts according to their respiratory conditions. Italian Journal of Zoology. 63:3, 201-206). Spleen size can increase as the temperature declines for adults – in larvae, there is no dramatic change in spleen size.(Frangioni, G., G Borgioli. 1997. Blood and splenic respiratory compensation in larval newts. Italian Journal of Zoology. 64:3, 221-226) During hibernation, an increase in liver pigment cells allows for storage of oxygen, as well as other important ions and free radicals.(Barni et al 1999)


Osmoregulation

In experiments, dehydrated eastern newts were prone to a loss of motor control: After only 22% water weight loss, newts in the aquatic phase lost their ability to remain upright and mobile. However, after adaptation to a terrestrial phase, they could lose 30% before a loss of motor control was recorded. Newts in the terrestrial phase were found to dehydrate much quicker than newts in the aquatic phase, but conversely, during rehydration, dehydrated terrestrial animals will go through water gain 5x faster than dehydrated newts that are in the aquatic phase.P. Walters, L. Greenwald. 1977. Physiological adaptations of aquatic newts (Notophtalmus viridescens) to a terrestrial environment. Physiological Zoology. 50(2): 88-98. In the Italian crested newt, it was shown that during winter months,
prolactin Prolactin (PRL), also known as lactotropin, is a protein best known for its role in enabling mammals to produce milk. It is influential in over 300 separate processes in various vertebrates, including humans. Prolactin is secreted from the pi ...
is released into the circulatory system, which drives the newts into the aquatic environment and reduces the active transport of sodium ions.Lodi, G., Biciotti, M., and Viotto, B. 1981. Cutaneous Osmoregulation in Triturus cristatus carnifex (Laur.) (Urodela). General and Comparative Endocrinology 46: 452-457. In contrast to prolactin, which decreases osmotic permeability,
vasotocin Vasotocin is an oligopeptide homologous to oxytocin and vasopressin found in all non-mammalian vertebrates (including birds, fishes, and amphibians) and possibly in mammals during the fetal stage of development. Arginine vasotocin (AVT), a hormone ...
increases the permeability and is secreted during the summer months.Brown, M., Brown, S., Bisceglio, I., and Lemke, S. 1983. Breeding Condition, Temperature, and the Regulation of Salt and Water by Pituitary Hormones in the Red-Spotted Newt, Notophthalmus viridescens. General and Comparative Endocrinology 51, 292-302. Arginine vasotocin not only increases cutaneous water permeability, but promotes increased cutaneous blood flow.Minoru Uchiyama, Norifumi Konno, Hormonal regulation of ion and water transport in anuran amphibians, General and Comparative Endocrinology, Volume 147, Issue 1, 15 May 2006, Pages 54-61,


Thermoregulation

Thermoregulation, in combination with seasonal acclimation, describes the major mechanisms of how newts, as ectotherms cope with the changing temperatures existing in their environments. This regulation is most often achieved through behavioral thermoregulation.(M. Hadamova, L. Gvozdik. 2011. Seasonal acclimation of preferred body temperatures improves the opportunity for thermoregulation in newts. Physiological and Biochemical Zoology. 84(2):166-174. ) They are thermoconformers, which means they will acclimate to their surrounding environmental temperatures. When there is a large range of environmental temperatures, newts are insensitive to a thermal gradient profile.(V. Marek, L. Gvozdik. 2012. The insensitivity of thermal preferences to various thermal gradient profiles in newts. Journal of Ethology. 30(1): 35-41) To escape predators, newt larvae have been found to shift their microhabitat to a temperature range that exists outside the predator's preferred temperature range.(R. Smolinsky, L. Gvozdik. 2009. The ontogenetic shift in thermoregulatory behavior of newt larvae: testing the “enemy-free temperature” hypothesis. Journal of Zoology. 279(2): 180-186. doi: 10.1111/j.1469-7998.2009.00603.x) Larvae that are in the metamorphosizing stage tend to prefer warmer temperatures than those in the stage following metamorphosis. Therefore, the larvae in this stage will undergo a much more precise thermoregulation process than those in the intermediate stage. Reproductive females of the Italian crested newt were shown to regulate their body temperature more precisely and prefer higher temperatures than non-reproductive females and males.(L. Gvozdik. 1995. Does reproduction influence temperature preference in newts. Canadian Journal of Zoology. 83(8): 1038-1044. doi: 10.1139/z05-096)


Susceptibility to pollution

Larvae, with their great number of lamellae in their gills,(Brunelli, E., E. Sperone, M. Maisano, and S. Tripepi. 2009. Morphology and ultrastructure of the gills in two Urodela species: Salamandrina terdigitata and Triturus carnifex. Italian Journal of Zoology. 76(2): 158-164) are more susceptible to pollutants than adults.
Cadmium Cadmium is a chemical element with the Symbol (chemistry), symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12 element, group 12, zinc and mercury (element), mercury. Li ...
, a heavy metal released into the environment from industrial and consumer waste, has been shown to be detrimental to the
Italian crested newt The Italian crested newt (''Triturus carnifex'') is a species of newt in the family Salamandridae. Habitat ''Triturus carnifex'' is found in parts of the Balkans and Italy. It is an aquatic breeder that can spend up to four months in the wat ...
even at a concentrations below Italian and European thresholds, by disrupting the activity of the
adrenal gland The adrenal glands (also known as suprarenal glands) are endocrine glands that produce a variety of hormones including adrenaline and the steroids aldosterone and cortisol. They are found above the kidneys. Each gland has an outer cortex ...
.(Gay, F., V. Laforgia, I. Caputo, C. Esposito, M. Lepretti, and A. Capaldo, “Chronic Exposure to Cadmium Disrupts the Adrenal Gland Activity of the Newt Triturus carnifex(Amphibia, Urodela),” BioMed Research International.) In experiments allowing Italian crested newts to be exposed to nonylphenol, an
endocrine disruptor Endocrine disruptors, sometimes also referred to as hormonally active agents, endocrine disrupting chemicals, or endocrine disrupting compounds are chemicals that can interfere with endocrine (or hormonal) systems. These disruptions can cause ...
common in leakage from sewers, there was a decrease in
corticosterone Corticosterone, also known as 17-deoxycortisol and 11β,21-dihydroxyprogesterone, is a 21-carbon steroid hormone of the corticosteroid type produced in the cortex of the adrenal glands. It is of minor importance in humans, except in the very rar ...
and
aldosterone Aldosterone is the main mineralocorticoid steroid hormone produced by the zona glomerulosa of the adrenal cortex in the adrenal gland. It is essential for sodium conservation in the kidney, salivary glands, sweat glands, and colon. It plays a c ...
, hormones produced by the
adrenal gland The adrenal glands (also known as suprarenal glands) are endocrine glands that produce a variety of hormones including adrenaline and the steroids aldosterone and cortisol. They are found above the kidneys. Each gland has an outer cortex ...
and important for stress response.(A. Capaldo, F. Gay, S. Valiante, M. DeFalco, R. Sciarrillo, M. Maddaloni, V. Laforgia. 2012. Endocrine-disrupting effects of nonylphenol in the newt, Triturus carnifex (Amphibia, Urodela). Comparative Biochemistry and Physiology. 155(2): 352-358. doi: 10.1016/j.cbpc.2011.10.004)


Conservation status

Although some species, such as the
rough-skinned newt The rough-skinned newt or roughskin newt (''Taricha granulosa'') is a North American newt known for the strong toxin exuded from its skin. Appearance A stocky newt with rounded snout, it ranges from light brown to olive or brownish-black on ...
(''Taricha granulosa'') and Eastern newt (''Notophthalmus viridescens)'' in North America or the smooth newt (''Lissotriton vulgaris'') in Europe, are still relatively common, populations of newts throughout their distribution range suffer from
habitat loss Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...
, fragmentation, and
pollution Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, th ...
. This affects especially the aquatic breeding sites they depend on, but also their land habitats. Several species, such as the Edough ribbed newt (''Pleurodeles poireti''),
Kaiser's spotted newt ''Neurergus kaiseri'', the Luristan newt, Kaiser's mountain newt, Kaiser's spotted newt or emperor spotted newt (not to be confused with '' Tylototriton shanjing''), is a species of very colourful salamander in the family Salamandridae. It is en ...
(''Neurergus kaiseri''), or the
Montseny brook newt The Montseny brook newt ( ca, tritó del Montseny; ''Calotriton arnoldi'') is a species of salamander in the family Salamandridae. It is endemic to the Montseny Massif (Catalan Pre-Coastal Range) in northeast Spain. Before it was formally descri ...
(''Calotriton arnoldi'') are considered threatened by the
IUCN The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...
, and the Yunnan lake newt is an example of a newt species that has gone extinct recently. 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 The Wildlife and Countryside Act 1981 is an Act of Parliament in the United Kingdom implemented to comply with European Council Directive 79/409/EEC on the conservation of wild birds. In short, the act gives protection to native species (especia ...
and the Habitat Regulations Act 1994. It is illegal to catch, possess, or handle
great crested newts The northern crested newt, great crested newt or warty newt (''Triturus cristatus'') is a newt species native to Great Britain, northern and central continental Europe and parts of Western Siberia. It is a large newt, with females growing up to ...
without a licence, or to cause them harm or death, or to disturb their habitat in any way. The
IUCN Red List The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is the world's most comprehensive inventory of the global conservation status of biolo ...
categorises the species as ‘lower risk’ Although the other UK species, the smooth newt and
palmate newt The palmate newt (''Lissotriton helveticus'') is a species of newt found in Western Europe, from Great Britain to the northern Iberian peninsula. It is long and olive or brown with some dark spots. The underside is yellow to orange, and the thr ...
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: *''
Calotriton asper The Pyrenean brook salamander or Pyrenean newt ( an, guardafuents pirenenco; ca, tritó pirinenc; eu, uhandre piriniarra; es, tritón pirenaico), ''Calotriton asper'', is a largely aquatic species of salamander in the family Salamandridae. It ...
'' *''
Euproctus montanus The Corsican brook salamander or Corsican mountain newt (''Euproctus montanus'') is a species of salamander in the family Salamandridae. It is endemic to Corsica, an island in the Mediterranean Sea. The Corsican brook salamander is found primari ...
'' *''
Euproctus platycephalus ''Euproctus'', the European mountain salamanders, is a genus of salamanders in the family Salamandridae from Sardinia and Corsica. Species There are two species: The Pyrenean brook salamander used to be included in this genus as ''Euproctus ...
'' *'' Lissotriton italicus'' *''
Lissotriton montandoni The Carpathian newt, or Montandon’s newt, (''Lissotriton montandoni'') is a species of salamander in the family Salamandridae found in Czech Republic, Poland, Romania, Slovakia, and Ukraine. The total length of adults of this species is arou ...
'' *''
Triturus carnifex The Italian crested newt (''Triturus carnifex'') is a species of newt in the family Salamandridae. Habitat ''Triturus carnifex'' is found in parts of the Balkans and Italy. It is an aquatic breeder that can spend up to four months in the wate ...
'' *''
Triturus cristatus The northern crested newt, great crested newt or warty newt (''Triturus cristatus'') is a newt species native to Great Britain, northern and central continental Europe and parts of Western Siberia. It is a large newt, with females growing up to ...
'' *''
Triturus dobrogicus The Danube crested newt or Danube newt (''Triturus dobrogicus'') is a species of newt found in central and eastern Europe, along the basin of the Danube river and some of its tributaries and in the Dnieper delta. It has a smaller and more slender ...
'' *''
Triturus karelinii The southern crested newt (''Triturus karelinii'') is a terrestrial European newt. It is similar to the northern crested newt (''Triturus cristatus'') except larger and more robust. In 2013, the Balkan-Anatolian crested newt (''Triturus ivanbure ...
'' The remaining European species are listed as "protected fauna species" under appendix III.


As bioindicators

Newts, as with salamanders in general and other amphibians, serve as bioindicators because of their thin, sensitive skin and evidence of their presence (or absence) can serve as an indicator of the health of the environment. Most species are highly sensitive to subtle changes in the pH level of the streams and lakes where they live. Because their skin is permeable to water, they absorb oxygen and other substances they need through their skin. Scientists study the stability of the amphibian population when studying the water quality of a particular body of water.


As pets

Chinese warty newt The Chinese warty newt (''Paramesotriton chinensis'') is a species of salamander in the family Salamandridae. It is found only in China, with a range extending from Chongqing to Hunan, Anhui, Zhejiang, Fujian, Guangdong, and Guangxi Provinces i ...
s, Chinese fire belly newts, eastern newts, paddletail newts, Japanese fire belly newts, Chuxiong fire-bellied newts, '' Triturus'' species,
emperor newt ''Tylototriton shanjing'', the emperor newt, Mandarin newt or Mandarin salamander, is a highly toxic newt native to China. Description ''Tylototriton shanjing'' can grow up to long. It has a ridged orange head from which a single orange ridge ...
s,
Spanish ribbed newt The Iberian ribbed newt, gallipato or Spanish ribbed newt (''Pleurodeles waltl'') is a newt endemic to the central and southern Iberian Peninsula and Morocco. It is the largest European newt species and it is also known for its sharp ribs which ...
s ( leucistic genes exist), and red-tailed knobby newts are some commonly seen newts in the pet trade. Some newts rarely seen in the pet trade are
rough-skinned newt The rough-skinned newt or roughskin newt (''Taricha granulosa'') is a North American newt known for the strong toxin exuded from its skin. Appearance A stocky newt with rounded snout, it ranges from light brown to olive or brownish-black on ...
s,
Kaiser's spotted newt ''Neurergus kaiseri'', the Luristan newt, Kaiser's mountain newt, Kaiser's spotted newt or emperor spotted newt (not to be confused with '' Tylototriton shanjing''), is a species of very colourful salamander in the family Salamandridae. It is en ...
s, banded newts and yellow-spotted newts.


References


External links

* {{Authority control * Extant Late Cretaceous first appearances