Description
The description of Tylototriton vietnamensis was based on three male specimens. No females were described. The snout-vent length ranged from 48.3 – 53.6 mm and the total length from 113.9 - 121.8 mm. Tylototriton vietnamensis has a moderately robust body with a head that is wider than its torso and slightly sloping when viewed in profile. The skull is broad. When viewed dorsally, the snout is short and truncate while in a profile view it is rounded and extends past the lower jaw. The nostrils in this species are positioned close to the end of the snout. Beneath the eyes, the thick and fleshy upper lip protrudes over the lower lip. Its maxillary teeth are positioned angular to the body axis. Two rows of vomeropalatine teeth start behind the last maxillary tooth, and the tongue of this species has a poorly developed tongue pad that does not have a free posterior margin (Böhme et al. 2005).

Tylototriton vietnamensis has small, rounded vertebral skin projection that extends down its back, like a ridge, following the path of its thirteen trunk vertebrae from the top of its head to the base of its tail. Two more ridges are present in the form of two lateral rows of larger warts that run from the insertion of the forearms to the base of the tail while smaller warts and glands cover the rest of the dorsal surface. These warts and glands do not extend to the ventral side, which is almost smooth in comparison. Enlarged paratoid glands are present on either side of the head and protrude slightly backward. Tylototriton vietnamensis lacks a gular fold and webbing between the fingers. It does, however, have basal webbing between the toes (Böhme et al. 2005).

The laterally compressed tail of T. vietnamensis has a moderately developed dorsal and ventral tail fin and acuminate tail tip when viewed in profile (Böhme et al. 2005).

The larval stage of this species has not been described, but the total length of one specimen was given as 45 mm. The larva of this species possesses large feathery gills that are absent in adults (Böhme et al. 2005).

Tylototriton vietnamensis is similar to several other species all within the genus Tylototriton. It is distinguished from other species such as Tylototriton kweichowensis and Tylototriton shanjing by its more slender body as well as the lack of orange-yellow markings on its dorsal area and an orange or yellow tail. It is smaller in size than Tylototriton verrucosus, and does not possess an orange or yellowish color on its dorsal area, tail, and flanks and exhibits a head that is wider than its body. Unlike Tylototriton taliangensis, it is lighter in color (tan compared to black), is stouter in shape, and does not possess red markings near the posterior corners of the parotoids. Compared to Tylototriton wenxianensis, T. vietnamensis has a greyish to brownish tan dorsal color instead of black, a shortened snout instead of rounded, and obvious, slightly flattened rib nodules that form ridges, whereas T. wenxianensis has inconspicuous rib nodules and ridges. Tylototriton vietnamensis can also be distinguished from Tylototriton asperrimus by its less protruding rib nodules and less distinct bony ridges on head. Unlike Tylototriton hainanensis, T. vietnamensis is smaller, has a light-colored dorsal area, and less rounded snout (Böhme et al. 2005).

The dorsal color of live specimens is a consistent greyish tan to brownish. The ventral side is tan while the rib nodules are tinged an orange-tan. Tylototriton vietnamensis has a yellow-orange ventral tail fin as well as yellow-orange finger and toe tips (Böhme et al. 2005).

In preservative, T. vietnamnesis’ dorsal and ventral color both become brownish tan. The finger and toe tips change from yellow-orange to cream-colored. The tail becomes brownish tan while the ventral tail fin becomes creamy-yellow along with the border around the cloacal region (Böhme et al. 2005).

Some variation was present in individuals of T. vietnamensis. Paratypes of this species displayed more extensive webbing on their toes, when compared to the holotype. In addition, individuals found in ponds have a lighter dorsal color while those found on the forest floor are darker in appearance (Böhme et al. 2005).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Viet Nam

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (6 records).

Tylototriton vietnamensis is found only in northeastern Vietnam in the Bac Giang and Quang Ninh provinces with an estimated extent of occurrence of 1,345 km² (IUCN). It is more commonly associated with higher elevations (Bernardes et al. 2013), occurring at an elevation range between 181 to 512 meters above sea level (IUCN). It occurs in lowland evergreen forests that have bamboos, hardwoods, and shrubs (IUCN). The biggest population is present in the Tay Yen Tu Nature Reserve. Most of their suitable habits are not in protected areas (Bernardes et al. 2013). Like other Tylototriton species in Vietnam, populations are typically distributed irregularly and are rare (Thien et al. 2013).

Life History, Abundance, Activity, and Special Behaviors
Tylototriton vietnamensis breeds during the rainy season in shallow ponds and pools that form on the secondary forest floor (Böhme et al. 2005). They are otherwise terrestrial (IUCN). In breeding sites in the Tay Yu Ten Nature Reserve and Yen Tu Protection Area, the breeding areas range between 0 - 460 m² on average. The species is absent in ponds with high concentrations of nitrates and nitrites, as well as ponds with a pH below 4.3 (Bernardes et al. 2013). Females are ovoviviparous and lay eggs in water that hatch into aquatic larvae and develop in the ponds (IUCN; Bernardes et al. 2013).

Larvae were found from June to October (Böhme et al. 2005).

Trends and Threats
The current population of T. vietnamensis is declining (Ziegler 2010). This trend is most likely due to the species’ main threats; habitat loss and the pet trade. (IUCN, Rowley et al. 2016)

Relation to Humans
Tylototriton vietnamensis is collected locally for traditional medical use and has also been known to show up from time to time in the pet trade (IUCN; Rowley et al. 2016; Thien et al. 2013)

Possible reasons for amphibian decline

General habitat alteration and loss
Intensified agriculture or grazing
Intentional mortality (over-harvesting, pet trade or collecting)

Comments
The species authority is: Böhme, W., Schöttler, T., Truong, N. Q., and Köhler, J. (2005). “A new species of salamander, genus Tylototriton (Urodela: Salamandridae), from Northern Vietnam.” Salamandra, 41(4), 215-220.

Tylototriton is a monophyletic group most closely related to the genus Echinotriton (Phimmachak et al. 2015; Weisrock et al. 2006). Tylototriton and Echinotriton are sister taxa in the family Salamandridae (Phimmachak et al. 2015). The genus Tylototriton includes many recently discovered species, including T. vietnamensis (Weisrock et al. 2006). Based on Bayesian analysis of 3,121 base pairs of mitochondrial DNA, T. vietnamensis falls under subgenus Yaotriton and is found to be most closely related to T. panhai (Phimmachak et al. 2015).

The species epithet comes from the country where it was discovered; Vietnam (Böhme et al. 2005).

According to a survey done in 2013 for chytrid fungus, Batrachochytrium dendrobatidis (Bd), in the genus Tylototriton, Bd was not present in any of the Tylototriton individuals collected and tested, concluding that Bd has not yet reached these vietnamese salamanders in northern Vietnam (Thien et al. 2013). However, their rarity, patchy distribution, and habitat conditions make them highly susceptible to Bd and are therefore in danger of possible extinction if Bd ever reached them (Thien et al. 2013).

Tylototriton vietnamensis, brought to Europe for the pet trade, have been found to carry Batrachochytrium salamandrivorans (Bsal), a chytrid fungus related to Bd. This fungus is thought to have originated in Asia where Asian salamanders, like T. vietnamensis, have evolved resistance to it; however, it has begun to spread to highly susceptible salamander populations in Europe due to the pet trade of these Asian salamanders who are carriers of the fungus (Martel et al. 2014).

In 2017, Laking et al. confirmed that Bsal was present in wild T. vietnamensis, along with seven other Southeast Asian species at low endemic levels (<3% prevalence). They also reported two key discoveries: Bsal and Bd co-existenced within populations, and Bsal was found in warmer than the expected water bodies.

The Cologne Zoo in Germany supports in situ conservation projects through WAZA (World Association of Zoos and Aquariums), including forest protection and research programs in Tay Yen Tu Nature Reserve, located in northeastern Vietnam, where T. vietnamensis has been found (Ziegler 2010). Tylototriton vietnamensis is currently being studied by scientists through student thesis work under the provision of Cologne Zoo’s WAZA projects.

Ex situ conservation efforts for T. vietnamensis have been carried out by the Cologne Zoo, which established a housing and breeding facility near Hanoi, Vietnam, in 2004. Tylototriton vietnamensis has been bred successfully in this facility since 2007 (Ziegler 2010).

References

Bernardes, M., Rödder, D., Nguyen, T. T., Pham, C. T., Nguyen, T. Q., and Ziegler, T. (2013). ''Habitat characterization and potential distribution of Tylototriton vietnamensis in northern Vietnam.'' Journal of Natural History, 47(17-18), 1161-1175.

IUCN SSC Amphibian Specialist Group. 2016. Tylototriton vietnamensis. The IUCN Red List of Threatened Species 2016: e.T135868A88920562. http://dx.doi.org/10.2305/IUCN.UK.2016-3.RLTS.T135868A88920562.en. Downloaded on 20 February 2017.

Martel, A., Blooi, M., Adriaensen, C., Van Rooij, P., Beukema, W., Fisher, M. C., Farrer, R. A., Schmidt, B. R., Tobler, U., Goka, Lips, K. K. R., Muletz,C., Zamudio, K. R., Bosch, J., Lötters, S., Wombwell, E., Garner, T. W. J., Cunningham, A. A., Spitzen-van der Sluijs, A., Salvidio, S., Ducatelle, R., Nishikawa, K., Nguyen, T. T., Kolby, J. E., Van Bocxlaer, I., Bossuyt, F., Pasmans, F. (2014). ''Recent introduction of a chytrid fungus endangers Western Palearctic salamanders.'' Science, 346(6209), 630-631.

Phimmachak, S., Aowphol, A., Stuart, B.L. (2015). ''Morphological and molecular variation in Tylototriton (Caudata: Salamandridae) in Laos, with description of a new species.'' Zootaxa, 4006(2), 285-310.

Rowley, J. J. L., Shepherd, C. R., Stuart, B. L., Nguyen, T. Q., Hoang, H. D., Cutajar, T. P., Wogan, G. O. U., Phimmachak, S. (2016). ''Estimating the global trade in Southeast Asian newts.'' Biological Conservation, 199(7), 96-100. [link]

Thien, T. N., Martel, A., Brutyn, M., Bogaerts, S., Sparreboom, M., Haesebrouck, F., Fisher, M. C., Beukema, W., Van, T. D., Chiers, K., Pasmans, F. (2013). ''A survey for Batrachochytrium dendrobatidis in endangered and highly susceptible Vietnamese salamanders (Tylototriton spp.).'' Journal of Zoo and Wildlife Medicine, 44(3), 627-633.

Weisrock, D. W., Papenfuss, T. J., Macey, J. R., Litvinchuk, S. N., Polymeni, R., Ugurtas, I. H., Zhao, E., Jowkar, H., Larson, A. (2006). ''A molecular assessment of phylogenetic relationships and lineage accumulation rates within the family Salamandridae (Amphibia, Caudata).'' Molecular Phylogenetics and Evolution, 41, 368-383.

Ziegler, T. (2010). “Breeding, Research, and Conservation of Tropical Herpetodiversity: Linking ex situ with in situ Approaches.” Paper presented 65th Annual WAZA Conference: Biodiversity is Life, Cologne, Germany. 73-76.

Species Account Citation: AmphibiaWeb 2017 Tylototriton vietnamensis: Vietnamese Crocodile Newt <https://amphibiaweb.org/species/6679> University of California, Berkeley, CA, USA. Accessed Nov 4, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 4 Nov 2024.

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