Triturus is a genus of newts comprising the crested and the marbled newts, which are found from Great Britain through most of continental Europe to westernmost Siberia, Anatolia, and the Caspian Sea region. Their English names refer to their appearance: marbled newts have a green–black colour pattern, while the males of crested newts, which are dark brown with a yellow or orange underside, develop a conspicuous jagged seam on their back and tail during their breeding phase.
Crested and marbled newts live and breed in vegetation-rich ponds or similar aquatic habitats for two to six months and usually spend the rest of the year in shady, protection-rich land habitats close to their breeding sites. Males court females with a ritualised display, ending in the deposition of a spermatophore that is picked up by the female. After fertilisation, a female lays 200–400 eggs, folding them individually into leaves of water plants. Larvae develop over two to four months before metamorphosing into land-dwelling juveniles.
Historically, most European newts were included in the genus, but taxonomists have split off the alpine newts (Mesotriton), the small-bodied newts (Lissotriton) and the banded newts (Ommatotriton) as separate genera. The closest relatives of Triturus are the European brook newts (Calotriton). Two species of marbled newts and seven species of crested newts are accepted, of which the Anatolian crested newt was only described in 2016. Their ranges are largely contiguous but where they do overlap, hybridisation may take place.
Although not immediately threatened, crested and marbled newts suffer from population declines caused mainly by habitat loss and fragmentation. Both their aquatic breeding sites and the cover-rich, natural landscapes upon which they depend during their terrestrial phase are affected. All species are legally protected in Europe, and some of their habitats have been designated as special reserves.
Taxonomy
The genus name Triturus was introduced in 1815 by the polymath Constantine Samuel Rafinesque, with the northern crested newt (Triturus cristatus) as type species. That species was originally described as Triton cristatus by Josephus Nicolaus Laurenti in 1768, but Linnaeus had already used the name Triton for a genus of sea snails ten years before, making a new genus name for the newts necessary.
Triturus included most European newt species until the end of the 20th century, but was substantially revised after it was shown to be polyphyletic. Three separate genera now accommodate former members of the genus: the small-bodied newts (Lissotriton), the banded newts (Ommatotriton), and the alpine newt (Ichthyosaura). The monophyly of the genus Triturus in the strict sense is supported by molecular data and synapomorphies such as a genetic defect causing 50% embryo mortality (see below, Egg deposition and development).
As of 2020, the genus contains seven species of crested newts and two species of marbled newts. Both groups were long considered as single species, Triturus cristatus and T. marmoratus, respectively. Substantial genetic differences between subspecies were, however, noted and eventually led to their recognition as full species, with the crested newts often collectively referred to as "T. cristatus superspecies". The Balkan and the Anatolian crested newt, the most recent species formally described (2013 and 2016, respectively), were only recognised through genetic data; together with the Southern crested newt, they form a cryptic species complex with no morphological differences known.
Description
Common characteristics
Triturus is a genus of rather large-bodied newts. They typically have a total length of between , with some crested newts of up to described. Size depends on sex and the environment: females are slightly larger and have a proportionally longer tail than males in most species, and the Italian crested newt seems to be larger in colder parts of its range.
Crested newts are dark brown, with black spots on the sides, and white stippling in some species. Their belly is yellow to orange with black blotches, forming a pattern characteristic for individuals. Females and juveniles of some species have a yellow line running down their back and tail. During breeding phase, crested newts change in appearance, most markedly the males. These develop a skin seam running along their back and tail; this crest is the namesake feature of the crested newts and can be up to 1.5 cm high and very jagged in the northern crested newt. Another feature of males at breeding time is a silvery-white band along the sides of the tail.
Marbled newts owe their name to their green–black, marbled colour pattern. In females, an orange-red line runs down back and tail. The crest of male marbled newts is smaller and fleshier than that of the crested newts and not indented, but marbled newt males also have a whitish tail band at breeding time.
Species identification Apart from the obvious colour differences between crested and marbled newts, species in the genus also have different body forms. They range from stocky with sturdy limbs in the Anatolian, Balkan and the southern crested newt as well as the marbled newts, to very slender with short legs in the Danube crested newt. These types were first noted by herpetologist Willy Wolterstorff, who used the ratio of forelimb length to distance between fore- and hindlimbs to distinguish subspecies of the crested newt (now full species); this index however sometimes leads to misidentifications.Action Plan for the Conservation of the Crested Newt Triturus cristatus Species Complex in Europe The number of rib-bearing vertebrae in the skeleton was shown to be a better species indicator. It ranges from 12 in the marbled newts to 16–17 in the Danube crested newt and is usually observed through radiography on dead or sedated specimens.
The two marbled newts are readily distinguished by size and colouration. In contrast, separating crested newt species based on appearance is not straightforward, but most can be determined by a combination of body form, coloration, and male crest shape. The Anatolian, Balkan, and southern crested newt however are cryptic, morphologically indistinguishable species. Triturus newts occupy distinct geographical regions (see Distribution), but hybrid forms occur at range borders between some species and have intermediate characteristics (see Hybridisation and introgression).
Based on the books of Griffiths (1996) and Jehle et al. (2011), with additions from articles on recently recognised species. NRBV = number of rib-bearing vertebrae, values from Wielstra & Arntzen (2011). Triturus anatolicus, T. ivanbureschi and T. karelinii are cryptic species and have only been separated through genetic analysis.
+ Image Species Length and build Back and sides Underside Male crest NRBV T. anatolicus (Anatolian crested newt),T. ivanbureschi (Balkan or Buresh's crested newt),T. karelinii (southern or Persian crested newt) 10–13 cm, exceptionally up to 18 cm; stocky Dark brown with black spots, heavy white stippling, white markings on cheeks Orange with numerous black spots, also on throat; tail underside bright orange Fairly indented 13 T. carnifex(Italian or alpine crested newt) Up to 17 cm (females); medium build, legs large Dark brown with black spots, no or little white stippling; females and juveniles often with yellow or greenish dorsal line Yellow or orange with some large, round, grey to black, blurred spots High 14 T. cristatus(northern or great crested newt) 15–16 cm; moderately slender, legs medium-sized Dark brown with black spots and white stippling Yellow or orange, black blotches with sharp edges Very high (up to 1.5 cm) and jagged 15 T. dobrogicus(Danube crested newt) 13–15 cm; slender, legs short Dark brown with black spots and white stippling Orange to red with small to medium-sized, well defined black blotches Very high and jagged, starting between eyes and nostrils 16–17 T. macedonicus(Macedonian crested newt) 14–16 cm; medium build, legs large Dark brown with black spots, dense white stippling on sides Yellow with black blotches smaller than in T. carnifex, not blurred High 14 T. marmoratus(marbled newt) 15–16 cm; stocky Dark-spotted, reticulate or marbled on green background; sometimes fine white stippling on flanks; females often with orange-red line from back to tail Blackish with fine white spots, but no yellow markings Fleshy, with vertical black bars 12 T. pygmaeus(southern or pygmy marbled newt) 10–12 cm; stocky Dark-spotted, reticulate or marbled on green background; females often with orange-red line from back to tail Yellow-cream with large black and smaller white spots Fleshy, with vertical black bars 12
Lifecycle and behaviour
Like other newts, Triturus species develop in the water as larvae, and return to it each year for breeding. Adults spend one-half to three-quarters of the year on land, depending on the species, and thus depend on both suitable aquatic breeding sites and terrestrial habitats. After larval development in the first year, juveniles pass another year or two before reaching maturity; in the north and at higher elevations, this can take longer. The larval and juvenile stages are the riskiest for the newts, while survival is higher in adults. Once the risky stages passed, adult newts usually attain an age of seven to nine years, although individuals of the northern crested newts have reached 17 years in the wild.
Aquatic phase
The aquatic habitats preferred by the newts are stagnant, mid- to large-sized, unshaded water bodies with abundant underwater vegetation but without fish, which prey on larvae. Typical examples are larger ponds, which need not be of natural origin; indeed, most ponds inhabited by the northern crested newt in the UK are human-made. Examples of other suitable secondary habitats are ditches, channels, gravel pit lakes, garden ponds, or (in the Italian crested newt) rice paddies. The Danube crested newt is more adapted to flowing water and often breeds in river margins, oxbow lakes or flooded marshland, where it frequently co-occurs with fish. Other newts that can be found in syntopy with Triturus species include the smooth, the palmate, the Carpathian, and the alpine newt.
Adult newts begin moving to their breeding sites in spring when temperatures stay above . This usually occurs in March for most species, but can be much earlier in the southern parts of the distribution range. Southern marbled newts mainly breed from January to early March and may already enter ponds in autumn. The time adults spend in water differs among species and correlates with body shape: while it is only about three months in the marbled newts, it is six months in the Danube crested newt, whose slender body is best adapted to swimming. Triturus newts in their aquatic phase are mostly nocturnal and, compared to the smaller newts of Lissotriton and Ichthyosaura, usually prefer the deeper parts of a water body, where they hide under vegetation. As with other newts, they occasionally have to move to the surface to breathe air. The aquatic phase serves not only for reproduction, but also offers the animals more abundant prey, and immature crested newts frequently return to the water in spring even if they do not breed.
Terrestrial phase