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Smooth newt

Smooth newt
Triturus vulgaris maennchen cropped.jpg
Male during land phase
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Amphibia
Order: Urodela
Family: Salamandridae
Genus: Lissotriton
Species:
L. vulgaris
Binomial name
Lissotriton vulgaris
(Linnaeus, 1758)
Subspecies[2]
  • L. vulgaris ampelensis (Mertens and Wermuth, 1960)
  • L. vulgaris meridionalis (Boulenger, 1882)
  • L. vulgaris vulgaris (Linnaeus, 1758)
Lissotriton vulgaris distribution.svg
Synonyms

Over 60,[3] including:

  • Lacerta vulgaris Linnaeus, 1758
  • Triton palustris Laurenti, 1768
  • Molge punctata Merrem, 1820
  • Triturus vulgaris Dunn, 1918

The smooth newt, northern smooth newt or common newt (Lissotriton vulgaris) is a species of newt. It is widespread in much of Eurasia, from the British Isles to Central Asia, and introduced to Australia. Individuals are brown with an orange to white, spotted underside and reach a total length of 8–11 cm (3.1–4.3 in), with males being larger than females. The dry and velvety skin becomes smooth during the aquatic phase. Breeding males develop a more vivid colour pattern and a conspicuous skin seam (crest) on their back.

Originally described by Carl Linnaeus as a lizard, the smooth newt was later classified in the newt genus Triturus before being placed in Lissotriton. Three subspecies are currently accepted. Four former subspecies, all with more restricted ranges, are now classified as separate species, as they are distinct in appearance and genetically: the Caucasian, the Greek, Kosswig's and Schmidtler's smooth newt. Together with the smooth newt and the Carpathian newt, they form a complex of closely related species, some of which hybridise.

Smooth newts live on land for most of the year, where they are mostly nocturnal and hide during the day. They can adapt to a wide range of natural or semi-natural habitats, from forests over field edges to parks and gardens. The newts feed mainly on various invertebrates such as insects or earthworms and are themselves eaten by predators such as fish, birds or snakes. Between spring and summer, they breed in ponds or similar water bodies. Males court females with a ritualised underwater display. Females then lay their eggs on water plants, and larvae hatch after 10 to 20 days. They develop over around three months before metamorphosing into terrestrial juvenile efts. Maturity is reached after two to three years, and adults can reach an age of up to 14 years.

The smooth newt is one of the most common newts and classified as Least Concern species. It is however negatively affected by habitat destruction and fragmentation and the introduction of fish. Like other European amphibians, it is listed in the Berne Convention as a protected species.

Taxonomy

Swedish naturalist Carl Linnaeus described the smooth newt in 1758 as Lacerta vulgaris, placing it in the same genus as the green lizards.[4]:206 Later, the species was included in the genus Triturus, along with most European newts. This genus however was found to be polyphyletic, containing several unrelated lineages,[5][6][7] and the small-bodied newts, including the smooth newt, were therefore split off as separate genus Lissotriton in 2004.[8]:233 This genus name had first been introduced by the English zoologist Thomas Bell in 1839, and the smooth newt is the genus' type species.[9]:132 "Lissotriton" is a combination of Greek λισσός, lissós for "smooth" and the name of Triton, the ancient Greek god of the sea, while the species epithet vulgaris means "common" in Latin.[10]:17

Three subspecies are accepted: L. v. vulgaris, L. v. ampelensis and L. v. meridionalis. Four former subspecies from southern Europe and west Asia are now recognised as separate species, as they are morphologically and genetically distinct: the Greek smooth newt (L. graecus), Kosswig's smooth newt (L. kosswigi), the Caucasian smooth newt (L. lantzi) and Schmidtler's smooth newt (L. schmidtleri). The five smooth newt species and the Carpathian newt (L. montadoni), which is their sister species, have collectively been referred to as the "smooth newt species complex".[3][2][11]

To distinguish the smooth newt from its close relatives, the English name "northern smooth newt" has been suggested.[11] Other common names that have been used in the literature include: common newt, great water-newt, common water-newt, warty eft, water eft, common smooth newt, small newt, small eft, small evet, and brown eft.[3]

Description

Newt on soil, lying on the side and exposing its orange, black-spotted underside
Males have dark, round spots on throat and belly.
Swimming male newt, with well developed crest and bright colours
During breeding season, males develop vivid colours and a crest.
Detail of male newt showing swollen, dark-coloured cloaca
The cloaca is swollen in breeding males.
Female newt under water, sitting on leaf
Breeding females are drab in colour and have no dorsal crest.

General characteristics

Adult males of the smooth newt reach around 9–11 cm (3.5–4.3 in) head-to-tail length and are thus – as an exception among newts – slightly larger than the females, which reach 8–9.5 cm (3.1–3.7 in). The head is longer than wide, with 2–3 longitudinal grooves, and the elongated snout is blunt in the male and rounded in the female. Outside the breeding season, both sexes are yellow-brown, brown or olive-brown. The male has dark, round spots, while the females have smaller spots which sometimes form two or more irregular lines along the back. Males have an orange strip on the tail underside, and throat and belly in males are orange to white with small dark, rounded spots (lighter and with smaller spots in the female).[10]:80[12]:233–234

The body weight of adults varies between 0.3 and 5.2 g, and decreases during the breeding season. Size and colour vary with environment, and the newts tend to be smaller in northern latitudes. The skin is velvety and water-repellent on land but smooth during the aquatic phase; it contains mucus and toxin glands and its upper layer is shed off regularly. Albinistic and leucistic individuals have been described.[10]:80-93

The smooth newt is diploid and has 24 chromosomes.[10]:107

Breeding characteristics

During the aquatic breeding season, males develop a skin seam or crest, which runs uninterruptedly along the back and the tail. It is 1–1.5 mm high at mid-body, but higher along the tail. The tail also has a lower fin, and its end is pointed. The cloaca of breeding males is swollen, round and dark-coloured. The hindfeet have more or less well developed toe flaps, depending on the subspecies. Colours in general are more vivid than during the land phase. The dark spots grow larger, and the crest often has vertical dark and bright bands. The lower edge of the tail is red with a silver-blue flash and black spots. Females only develop low, straight tail fins but no crest or toe flaps, and are more drably coloured.[13]:26[12]:233–234

Subspecies differ slightly in male secondary characteristics: L. v. ampelensis has strongly developed toe flaps, its tail tapers into a fine thread (but not a distinct filament), and the body is slightly square in cross-section. L. v. meridionalis also has toe flaps and a pointed tail, its crest is smooth-edged, and its body is square-shaped. In the nominate subspecies, L. v. vulgaris, the crest is clearly denticulated, toe flaps are only weakly developed and the body is round.[12]:234–236

Larvae

The aquatic larvae are 6.5–7 mm long and yellow-brown with two longitudinal stripes at hatching. They initially have only two balancers at the sides of the head, which get resorbed within a few days.[12]:237 As in all salamanders, forelegs develop before the hindlegs. The colour becomes a more cryptic, darkly marbled yellow to brown in the growing larvae. Larvae are very slender and similar to the palmate newt (L. helveticus). They develop a skin seam from the neck to the pointed tail; the tail is as long as the head and trunk. The larvae grow to 3–4.5 cm (1.2–1.8 in) just before metamorphosis.[10]:188-192

Similar species

The smooth newt resembles the other, less widespread Lissotriton species. It can be confused especially with the closely related "smooth newt complex" species (marked with * in the table below) and the more distant palmate newt, which often occurs in the same area.[11][10]:25 Females are especially difficult to tell apart, as distinguishing features are mainly observed in the males at breeding season.[10]:19–41[12]:225–235

Comparison of the smooth newt and related Lissotriton species[10]:19–41[12]:225–235
Species Distribution Breeding male characteristics Other
Body shape Dorsal crest Toe flaps (hind feet) Tail end
Smooth newt*
L. vulgaris
widespread from British Isles to Central Asia round to square (depending on subspecies) smooth or denticulated (depending on subspecies) weakly to well developed (depending on subspecies) pointed to elongated, no filament
Bosca's newt
L. boscai
West Iberian peninsula slightly square none none short filament belly with some dark spots, especially at sides
Carpathian newt*
L. montandoni
Carpathians square very low, smooth-edged weakly developed blunt, with filament belly unspotted
Caucasian smooth newt*
L. lantzi
Caucasus slightly square high (>1 mm at mid-body), denticulated (almost spine-shaped) moderately developed pointed, but no filament
Greek smooth newt*
L. graecus
Southern Balkans square low (<1 mm at mid-body), smooth-edged well developed long filament lower tail fin unspotted
Italian newt
L. italicus
Southern Italy slightly square none none pointed, no filament very small, 4.5–7.5 cm (1.8–3.0 in); throat with few or no spots; golden-yellow patch behind eyes in both sexes
Kosswig's smooth newt*
L. kosswigi
Northern Anatolia square low (<1 mm at mid-body) but higher at tail base strongly developed long filament
Palmate newt
L. helveticus
Western Europe square low, smooth-edged strongly developed long filament (both sexes) throat unspotted
Schmidtler's smooth newt*
L. schmidtleri
Anatolia and eastern Balkans slightly square high (>2 mm at mid-body), denticulated weakly developed elongated, no filament very small, 5–7 cm (2.0–2.8 in)

Distribution

Native range

The smooth newt has been described as "the most ubiquitous and widely distributed newt of the Old World".[12]:237 It ranges natively from Ireland (where it is the only newt species) and Great Britain in the west to central Asia (Siberia and northern Kazakhstan) in the east. In the north it reaches central Fennoscandia, and its southern limit is central France, southern Italy, the central Balkans and the dry Eurasian steppe of Ukraine and Russia.[14][11][12]:234–238[10]:42–44

The nominate subspecies, L. v. vulgaris, is most widespread. L. v. ampelensis only occurs in the Carpathians of Ukraine and the Danube delta of northern Romania, and L. v. meridionalis in the northern half of Italy, southern Switzerland, Slovenia and Croatia.[12]:234–235 In the Carpathians, the smooth newt generally prefers lower elevations than the Carpathian newt. In the Balkans, the precise contact zones with the Greek smooth newt and Schmidtler's smooth newt are not yet clear.[11]

Introduced range

The nominate subspecies, L. v. vulgaris, has been introduced to Australia. It was first recorded near Melbourne in 2011, and larvae were later found. This made it the first naturalised salamander species in the southern hemisphere. The newts probably originated from the pet trade, through which they were available before being declared a "controlled pest animal" in 1997. Negative impacts on the native fauna were feared, including predation and competition, toxicity, and disease spread. The smooth newt could spread further in south-eastern Australia, where wide areas have a suitable climate.[15]

Habitats

Sunny, water-filled ditch at the edge of f forest
Sun-exposed, shallow water bodies with abundant vegetation, such as this ditch, are typical breeding sites.

Mainly a lowland species, the smooth newt is only exceptionally found above 1,000 m (3,300 ft).[10]:78–80 It accepts a wide range of terrestrial and aquatic habitats. On land, it occurs in wooded areas (dense conifer woods are avoided) but also in more open areas such as damp meadows, field edges, parks and gardens. It readily adapts to urban environments. The newts hide under structures such as logs or stones or in small mammal burrows.[10]:120–134[14][12]:238

Aquatic breeding sites must be close to the land habitats. They are typically sun-exposed, free from fish, stagnant, permanent or water-filled for at least three months, close to similar water bodies, and have shallow areas with abundant water plants. They can range from small puddles to larger ponds or shallow parts of lakes. Water quality is less important; pH values from 4 to 9.6 are tolerated and in Germany, smooth newts have even been found in slightly brackish water.[10]:121–129 They often share breeding sites with other amphibians, including other newts; in northern France, ponds with five newt species – smooth, palmate, alpine (Ichthyosaura alpestris), northern crested (Triturus cristatus) and marbled newt (T. marmoratus) – have been described.[10]:151–152

Lifecycle and behaviour

Smooth newts live on land during most of the year and are mainly nocturnal. They also usually hibernate on land, often in congregations of several newts in shelters such as under logs or in burrows. The efts turn into mature adults at two to three years, and an overall age of 6–14 years can be reached in the wild.[12]:238

Reproduction

External video
video icon The life cycle of the newt, British Council, 1942. Educational film on the smooth newt (10:08 min).
Newt larva with feathery gills in side view
Well-developed larva shortly before metamorphosis
Two brown juvenile newts sitting closely together
Two juveniles (efts) after the transition to land

Migration to the breeding sites occurs as soon as February, but in the northern parts of the range and at higher altitudes, it may not start before summer. After entering the water, the breeding characters, especially the male's crest, take a few weeks to develop.[12]:238

Mating involves an intricate courtship display: The male attempts to attract a female's attraction by swimming in front of her and sniffing her cloaca. He then vibrates his tail against his body, sometimes violently lashing it, thereby fanning pheromones towards her. In the final phase, he moves away from her, the tail quivering. If she is still interested, she will follow him and touch his cloaca with her snout, whereupon he deposits a packet of sperm (a spermatophore). He then guides her over the spermatophore so she picks it up with her cloaca. Males often try to lead females away from displaying competitors.[12]:238–240

Eggs are fertilised internally, and progeny of one female usually has multiple fathers. It has been shown that females tend to mate preferentially with unrelated males, probably to avoid inbreeding depression.[16]

Females lay 100–500 eggs, usually folding them into waterplants. The eggs are 1.3–1.7 mm in diameter (2.7–4 mm with jelly capsule) and light brown to greenish or grey in colour. Larvae typically hatch after 10–20 days, depending on temperature, and metamorphose into terrestrial efts after around three months. Paedomorphism, where adults retain their gills and stay aquatic, occurs regularly.[12]:238–240

Diet and predators

Close-up view of snake eating a newt
Grass snake eating a smooth newt

Smooth newts, including the larvae, are unselective carnivores, feeding mainly on diverse invertebrates such as earthworms, snails or insects, or smaller plankton. Cannibalism also occurs, mainly by preying on eggs of its own species. Various predators eat smooth newts, including waterbirds, snakes and frogs, but also larger newts such as the northern crested newt.[12]:238

Evolution

Molecular phylogenetic analyses have shown that the smooth newt is distinct from its four close relatives – the Caucasian, Greek, Kosswig's, and Schmidtler's smooth newt – which were formerly considered subspecies (see section Taxonomy above). The relationships within this species complex have however have not been fully resolved. Within the smooth newt, and genetic groups do not completely match the currently accepted subspecies (ampelensis, meridionalis, vulgaris), described based on morphology.[2] The five smooth newt species collectively were estimated to have diverged from the Carpathian newt around four to six million years ago.[17][18]

Genetic analyses have also demonstrated ongoing gene flow between the smooth newt and its relatives. Although the Carpathian newt is morphologically clearly different, hybridisation between the two species is frequent;[10]:26 it has been shown that smooth newt mitochondrial DNA has introgressed into and completely replaced that of the Carpathian newt populations.[19] Partial introgression also occurred from the smooth newt to the Greek smooth newt.[2] These patterns are likely due to the range expansion and secondary contact of species after the Last Glacial Maximum, which they likely survived in refugia mainly in southern Europe[19][18] The palmate newt, although often occurring in the same habitats, almost never hybridises with the smooth newt.[10]:25 Artificial crosses with even more distant species such as the alpine and northern crested newt were however successful in laboratory experiments.[10]:29

Threats and conservation

The smooth newt is common over much of its range.[1][12]:237 The IUCN, in 2008, assessed its threat status as Least Concern and found no general decline in populations.[1] However, this assessment included subspecies now recognised as separate species (see section Taxonomy above) and needs updating.[11] Despite the overall low concern, the smooth newt is listed in some national red lists, e.g. in Switzerland, the Czech Republic, and the Netherlands.[10]:196 Like all amphibians, it is also listed as protected species in the Berne Convention (Appendix III).[20] Disturbance, capture, killing and trade are prohibited in Ireland under the Wildlife Act 1976,[21] and trade in the UK under the Wildlife and Countryside Act 1981.[22]

Threats to smooth newts are similar to those affecting other amphibians. They include especially the loss of breeding ponds through destruction or introduction of fish, and the fragmentation of population through roads.[10]:196-197 Secondary habitats can help sustain the species, e.g. former gravel pits or quarries left open.[10]:204-205 Garden ponds are readily colonised if they are sun-exposed, have abundant water plants, no fish, and hiding structures such as hedges or stone heaps in proximity.[10]:206-218 To track individuals and monitor populations, researchers have often amputated phalanges of fingers and toes but these re-grow quickly; a safer and less harmful alternative is recording the individual belly patterns through photography.[10]:223-224

Captivity

Smooth newts can be kept in captivity but must come from a legal source. They need a land and water phase, with hibernation for two to three months at 5–10 °C.[10]:210-215

References

  1. ^ a b c Arntzen, J.W.; Kuzmin, S.; Beebee, T.; et al. (2009). "Lissotriton vulgaris". IUCN Red List of Threatened Species. 2009: e.T59481A11932252. doi:10.2305/IUCN.UK.2009.RLTS.T59481A11932252.en. Retrieved 1 November 2020.
  2. ^ a b c d Pabijan, M.; Zieliński, P.; Dudek, K.; Stuglik, M.; Babik, W. (2017). "Isolation and gene flow in a speciation continuum in newts". Molecular Phylogenetics and Evolution. 116: 1–12. doi:10.1016/j.ympev.2017.08.003. ISSN 1055-7903. PMID 28797693.
  3. ^ a b c Frost, D.R. (2020). "Lissotriton vulgaris (Linnaeus, 1758). Amphibian Species of the World: an Online Reference. Version 6.1". New York, USA: American Museum of Natural History. doi:10.5531/db.vz.0001. Retrieved 18 April 2020. Cite journal requires |journal=
  4. ^ Linnaeus, C. (1767). Systema Naturae per Regna Tria Naturae, Secundum Classes, Ordines, Genera, Species, cum Characteribus, Differentiis, Synonymis, Locis (in Latin) (10 ed.). Stockholm, Sweden: L. Salvii. doi:10.5962/bhl.title.37256.
  5. ^ Titus, T.A.; Larson, A. (1995). "A molecular phylogenetic perspective on the evolutionary radiation of the salamander family Salamandridae". Systematic Biology. 44 (2): 125–151. doi:10.1093/sysbio/44.2.125. ISSN 1063-5157.
  6. ^ Weisrock, D.W.; Papenfuss, T.J.; Macey, J.R.; et al. (2006). "A molecular assessment of phylogenetic relationships and lineage accumulation rates within the family Salamandridae (Amphibia, Caudata)". Molecular Phylogenetics and Evolution. 41 (2): 368–383. doi:10.1016/j.ympev.2006.05.008. ISSN 1055-7903. PMID 16815049.
  7. ^ Steinfartz, S.; Vicario, S.; Arntzen, J.W.; Caccone, A. (2007). "A Bayesian approach on molecules and behavior: reconsidering phylogenetic and evolutionary patterns of the Salamandridae with emphasis on Triturus newts". Journal of Experimental Zoology Part B: Molecular and Developmental Evolution. 308B (2): 139–162. doi:10.1002/jez.b.21119. ISSN 1552-5007. PMID 16969762.
  8. ^ García-París, M.; Montori, A.; Herrero, P. (2004). Amphibia: Lissamphibia. Fauna Iberica. 24. Madrid: Museo Nacional de Ciencias Naturales, Consejo Superior de Investigaciones Científicas. ISBN 8400082923.
  9. ^ Bell, T. (1839). "A History of British Reptiles". London: John van Voorst. doi:10.5962/bhl.title.5498. Cite journal requires |journal=
  10. ^ a b c d e f g h i j k l m n o p q r s t u v Große, W-R. (2011). Der Teichmolch [The smooth newt]. Die neue Brehm-Bücherei (in German). 117. Magdeburg, Germany: VerlagsKG Wolf. ISBN 978-3-89432-476-6. ISSN 0138-1423.
  11. ^ a b c d e f Wielstra, B.; Canestrelli, D.; Cvijanović, M.; et al. (2018). "The distributions of the six species constituting the smooth newt species complex (Lissotriton vulgaris sensu lato and L. montandoni) – an addition to the New Atlas of Amphibians and Reptiles of Europe" (PDF). Amphibia-Reptilia. 39 (2): 252–259. doi:10.1163/15685381-17000128.
  12. ^ a b c d e f g h i j k l m n o p Sparreboom, M. (2014). Salamanders of the Old World: The Salamanders of Europe, Asia and Northern Africa. Zeist, The Netherlands: KNNV Publishing. doi:10.1163/9789004285620. ISBN 9789004285620.
  13. ^ Beebee, T & Griffiths, R. (2000) The New Naturalist: Amphibians and reptiles – a natural history of the British herpetofauna; Harper Collins Publishers, London.
  14. ^ a b Kuzmin, S. (1999). "AmphibiaWeb – Lissotriton vulgaris". Archived from the original on 19 April 2019. Retrieved 26 April 2020.
  15. ^ Tingley, R.; Weeks, A.R.; Smart, A.S.; et al. (2014). "European newts establish in Australia, marking the arrival of a new amphibian order" (PDF). Biological Invasions. 17 (1): 31–37. doi:10.1007/s10530-014-0716-z. hdl:11343/216887. ISSN 1387-3547. S2CID 18950725.
  16. ^ Jehle, R.; Sztatecsny, M.; Wolf, J.B.W; et al. (2007). "Genetic dissimilarity predicts paternity in the smooth newt (Lissotriton vulgaris)". Biology Letters. 3 (5): 526–528. doi:10.1098/rsbl.2007.0311. PMC 2391198. PMID 17638673.
  17. ^ Zieliński, P.; Nadachowska-Brzyska, K.; Dudek, K.; Babik, W. (2016). "Divergence history of the Carpathian and smooth newts modelled in space and time". Molecular Ecology. 25 (16): 3912–3928. doi:10.1111/mec.13724. ISSN 0962-1083. PMID 27288862. S2CID 206183624.
  18. ^ a b Pabijan, M.; Zieliński, P.; Dudek, K.; et al. (2015). "The dissection of a Pleistocene refugium: phylogeography of the smooth newt, Lissotriton vulgaris, in the Balkans". Journal of Biogeography. 42 (4): 671–683. doi:10.1111/jbi.12449. ISSN 0305-0270.
  19. ^ a b Babik, W.; Branicki, W.; Crnobrnja-Isailovic, J.; et al. (2005). "Phylogeography of two European newt species - discordance between mtDNA and morphology". Molecular Ecology. 14 (8): 2475–2491. doi:10.1111/j.1365-294X.2005.02605.x. ISSN 0962-1083. PMID 15969729. S2CID 7484766.
  20. ^ "Convention on the Conservation of European Wildlife and Natural Habitats". Bern: Council of Europe. 1979. Retrieved 1 November 2020.
  21. ^ Nelson, B.; Cummins, S.; Fay, L.; et al. (2019). "Checklists of protected and rare species in Ireland" (PDF). Irish Wildlife Manuals. National Parks and Wildlife Service, Department of Culture, Heritage and the Gaeltacht. 116. ISSN 1393-6670. Retrieved 1 November 2020.
  22. ^ "Wildlife and Countryside Act 1981". Article 9,Actof1981. United Kingdom.

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