Description
Laotriton laoensis is a salamander with a snout vent length of 83.6 ± 3.8 mm in males and about 82.2 ± 2.6 in females. It has a black heavy built physique with various dorsum orange-red spotting. The broad head has sloping profile and is proportional to the width of the body, head width about 21.4 ± 1.0 mm and about 28.2 ± 1.3 mm long; maxillaries are positioned angular to the axis of the body. The snout exceeds the lower jaw despite being short, truncated, and rounded in profile with the nares located near the tip; internostril distance about 5.7 ± 0.3 mm. Below the snout rests the lips, the fleshy bottom lip overlaps the upper thick lip under the eye area. Laotriton laoensis possess a total of three tubercular back ridges extending from the top of the head to the base of the tail: one midline and two lateral. Most of the dorsal and ventral surfaces are covered by glands and warts, has large backward projecting paratoids, and also posses a gular fold. As for the limbs, there are four fingers on each hand and five toes on each foot, all lacking webbing. The tail has a total length of 86.7 ± 4.5 mm and depth of 13.8 ± 1.0 mm, which is laterally compressed. Lastly, the dorsal tail fin and indistinct ventral tail fin are round in profile (Stuart and Papenfuss 2002).

Due to its broad skull with angular oriented maxillaries, morphological charactristics of the skeleton, hyoid apparatus of warty newts, and twelve trunk vertebrae, this species was initially allocated to the genus Paramesotriton. However further work demonstrated it was different enough to be in its own genus (Dubois & Rafaelli 2009; Frost 2011). The tan coloration of back stripes, warts, and glands help distinguish Laotriton Laoensis from all other Paramesotriton. It is slightly more difficult to distinguish from P. fuzhongensis physically but regionally P. fuzhongensis is found in China; L. laoensis is exclusive to a small geographic region of about 4,800 km² in Laos (see “Distribution and Habitat”). What makes Laotriton laoensis distinguishable from all other Asian salamandrides except Pachytriton is its reduced tongue pad lacking a free posterior margin. Even though Laotriton laoensis shares similar tongue characteristics with Pachytriton, the latter has a narrow skull with maxillaries oriented parallel to the body axis rather than oriented angular to the body axis. Concerning other Asian salamandrid genera, Cynops has thirteen trunk vertebrae, Echinotriton possesses a side row of large warts supported by rib tips, and lastly, Tylototriton has a uniformly pigmented venter and 13 - 15 trunk vertebrae, making them distinguishable from Laotriton laoensis and its 12 trunk vertebrae (Stuart and Pappenuss 2002).

Color in life is composed of an entire black body with tan tubercular dorsal ridges and parotoid glands. A spot on the back of the snout, dorsum of forelegs at junction with body, and some region extending obliquely from the back corner of the eye near the corner of the mouth are also tan. A very distinctive trait is the large irregular orange-red spots on the underside, chin, underside of axillae, and cloaca. Smaller similar spots are also present interspersed on venter and on underside of the tail base. Coloration in preservative tends to fade the tan dorsal stripes to yellow or white; back orange-red also fades to yellow or white (Stuart and Papenfuss 2002).

Males are slightly larger in almost every physical aspect: snout vent length, head length, head width, interocular distance, distance between anterior corner of the right eye to right nostril, internostril distance, distance between axillae on right side, right anterior limb length, right posterior limb length. Females tend to have larger tail lengths, tail depth, and total length. Other variations overall consists of the width of dorsal tan stripes, in some cases even merging to cover nearly the entire backside. Ventral spots also vary in shape and arrangement (Stuart and Papenfuss 2002).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Lao People's Democratic Republic

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (14 records).

Laotriton laoensis can be found in Northern Laos at seven localities in six streams in the Xaysamboun District of Vientiane Province, Phoukhout and Pek districts of Xiengkhouang Province, and Phoukhoun District of Louangphabang Province; it has a limited geographic region of about 4,800 km². Despite not having forest near, the streams are lined by tall grasses and banana trees with little to no shade from canopy on the streams. The terrain is mainly flat with substrate of silt, gravel, rocks, and submerged rocks. All streams are located approximately above 1,100 m elevation, and are small, cold (13 - 25 Celsius), slightly acidic, and contain rock substrate (Stuart and Papenfuss 2002; Phimmachak et al. 2012).

Life History, Abundance, Activity, and Special Behaviors
Laotriton laoensis can be seen actively moving in the sunlit pool bottoms of the Houay Sang Kat and Houay Pa Tin streams in Lao. Constantly emerging from rocks and crevices, they are cryptic even by day because of the tan dorsal markings that blend with the dappled sunlight in the pool bottom. Laotriton laoensis is considered to be fully aquatic but does occasionally move overland during and after heavy rain. Male diets consist of a wide variety of aquatic invertebrates, earthworms, and gastropods. Female diet consists of conspecific eggs in addition to what males eat. Mating tends to take part during the driest and coldest part of the year (November to February), this then enables the eggs to be laid for a long period between dead leaves on the bottom of stream pools; under observation the duration of the laying process took approximately 19 days. The larvae metamorphose into terrestrial efts after their initial aquatic state, terrestrial eft stage duration is unknown (Stuart and Papenfuss 2002; Phimmachak et al. 2012).

Trends and Threats
Laotriton laoensis was originally classified as “Data Deficient” but according to Phimmachak et al. (2012) it warranted “Endangered” status. Shortly after the first species description, which included the precise locality information, pet trade collectors exploited the locality and brought the species close to extinction in the wild. Scientists are now working closely with relevant governmental agencies to coordinate publication of the description with legislation or management plans that hinder overexploitation and avoid contributing to species decline (Stuart et al. 2006; Phimmachak et al. 2012).

Relation to Humans
Its few populations are heavily impacted by over-collection for the pet trade. See “Trends and Threats” section.

Possible reasons for amphibian decline

Intentional mortality (over-harvesting, pet trade or collecting)

Comments
Originally assigned to the Paramesotriton genus because of the skull and vertebral characters. Later, molecular analyses of the ND2 and the 12S-16S rDNA regions showed that this species as the sister taxon to a clade containing Paramesotriton and Pachytriton. An accumulation of these findings, distinct coloration, locality, and its unique morphology led to it being placed in its own genus, Laotriton (Gu et al. 2012; Phimmachak et al. 2012).

References

Dubois, A., Raffaelli, J. (2009). ''A new ergotaxonomy of the family Salamandridae Goldfuss, 1820 (Amphibia, Urodela).'' Alytes, (26), (1–4) (1–85). [link]

Gu, X., Wang, H., Chen, R., Tian, Y., Li, S. (2012). ''The phylogenetic relationships of Paramesotriton (Caudata: Salamandridae) based on partial mitochondrial DNA gene sequences.'' Zootaxa, (3150), 59-68.

Phimmachak, S., Stuart, B.L., Sivongxay, N. (2012). ''Distribution, Natural History, and Conservation of the Lao Newt (Laotriton laoensis) (Caudata: Salamandridae).'' Journal of Herpetology, 46(1), 120-128.

Stuart, B.L., Papenfuss, T.J. (2002). ''A new Salamander of the Genus Paramesotriton (Caudata: Salamandridae) from Laos.'' Journal of Herpetology, 36(2), 145-148.

Stuart, B.L., Rhodin, A.G.J., Grismer, L.L., Hansel, T. (2006). ''Scientific description can imperil species.'' Science (Washington D C), 312(5777), 1137.

Species Account Citation: AmphibiaWeb 2021 Laotriton laoensis: Laos Warty Newt; Laotriton de Laos <https://amphibiaweb.org/species/5980> University of California, Berkeley, CA, USA. Accessed Nov 21, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 21 Nov 2024.

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