Black Knobby Newt
|Taxonomic Notes: Fei, Ye & Jiang 2012 Colored atlas of Chinese amphibians place this species in what others consider subgenus Yaotriton. Tylototriton hainanensis was placed in the synonymy of T. asperrimus by Yuan et al 2011 Zool Res 32: 577-584.|
© 2006 Henk Wallays (1 of 8)
Country distribution from AmphibiaWeb's database: China, Viet Nam
Author: Axel Hernandez
Tylototriton asperrimus UNTERSTEIN 1930
Diagnosis and taxonomyOf the original two syntypic specimens, ZMB 34089 is now considered the holotype. While the Dayao crocodile newt was placed in the genus Echinotriton by ZHAO & HU (1988), more recent genetic studies suggest that T. asperrimus be better placed in Tylototriton (LARSON et al. 2003, WEISROCK et al. 2006, ZHANG et al. 2008, YUAN et al. 2011). It is characterized by a moderately large size of 13.8 cm TL at maximum (FEI et al. 2012), a flat and oval head that is slightly wider than long and has prominent bony ridges, a rounded snout, no labial fold, gular fold distinct, and body slender and flattened. When the limbs of one side are adpressed against the body, the digits will touch or slightly overlap. The vertebral ridge is distinct but low and segmented, the 10 - 13 dorsolateral glandular warts are present, the skin is rough with fine granules, small transverse wrinkles are present on the venter, and the tail is compressed laterally and tapering to a pointed tip (SPARREBOOM 2014). Its tail is shorter than the snout- vent length (ZHAO 1998). Males have a longer cloaca, in fact as long as the distance between the nostrils. Small papillae are present at the male’s cloaca, whereas the cloaca of a female will be much shorter and swollen during the breeding season (FEI et al. 2006, 2012). Tylototriton asperrimus is grayish black, with orange-red pigment being limited to the tips of the digits, cloaca and underside of the tail. It resembles T. wenxianensis and T. hainanensis, but differs from the former by its clearly separated, large, dorsolateral warts, and from the latter by a relatively narrower head and smaller body size. Some individuals have a few reddish orange dorsolateral warts, and in males living in the Dayao Mts., the rear parts of the parotoids will also be red during the breeding season (pers. obs.).
Some southern populations distributed in mountains in China and northern Vietnam are taxonomically problematic and classified in separate clades (Clade A: topotypic asperrimus, northeastern Guangxi to southern Guangdong; Clade B: T. cf. asperrimus “Baise”, western Guangxi; and Clade C: T. cf. asperrimus “Lao Cai/Hoa Binh”, northern Vietnam), of which T. asperrimus from Baise, Guangxi Province, in southern China (FEI et al. 2012, RAFFAËLLI 2007, 2013) is clustered with topotypic T. hainanensis and surely deserving of a new status (YUAN et al. 2011, PHIMMACHAK et al. 2015, HERNANDEZ 2016b, this study). On the other hand, recent phylogenies found that T. cf. asperrimus “Hoa Binh” and T. cf. asperrimus “Lao Cai” were morphologically and genetically similar and clustered with topotypic T. asperrimus in a separate clade (C) (NGUYEN et al. 2009, YUAN et al. 2011, HERNANDEZ 2015a, 2016a,b, PHIMMACHAK et al. 2015, this study). T. cf. asperrimus “Lao Cai”, of which a specimen from the Nam Tha Commune (21°55' N, 104°22' E, 850 m a.s.l.; Van Ban District, Lao Cai Province) might belong to an undescribed species within the supraspecies asperrimus and needs taxonomic revision, not at least for conservation purposes (HERNANDEZ 2016a,b). T. cf. asperrimus "Hoa Binh" is morphologically close to T. asperrimus, T. ziegleri and T. hainanensis. Adults are characterized by a large, wide head, short snout, enlarged parotoid glands, well-developed glandular and vertebral tubercular ridges, 15 to 17 large dorsolateral glandular warts on the dorsum, a laterally compressed tail, a dark brown coloration, and measuring about 13 - 14 cm TL (LUU et al. 2014).
DistributionThe type locality is the Dayaoshan National Nature Reserve, located in the central part of Guangxi Province, southern China, and actually lies in the vicinity of Luoxiang Township according to FAN (1931). This species is distributed in fragmented mountainous areas from southern Guizhou and northeastern Guangxi to southern Guangdong. In Guangxi Province, it is found from the northeastern part, Miao’er Shan, to the southern part at three known localities: Xian at Longsheng, Guilin; Xianglushan, Jinxiu County (at 1,116 m), and in the Melun National Nature Reserve. One population occurs in Libo County in Guizhou Province on the border to Guangxi. In southern Guangdong Province, a new population was found in Yangchun County, E’huangzhang Mountains during our field studies. The Baise population is located in southwestern Guangxi Province. These newts were found in subtropical rainforest mainly composed of bamboo at moderate elevations of about 750 to 1350 m a.s.l. Its distribution is not too far from topotypic T. asperrimus (Clade A) 200 km to the north, in the vicinity of Hechi Township and up to 300 km from the Vietnamese localities (Clade C). T. cf. asperrimus "Hoa Binh" has recently been found in the Thuong Tien Nature Reserve, Hoa Binh Province, Vietnam, and in the Cot Ca Forest, Quy Hoa Commune, Lac Son District, likewise in Hoa Binh, at an elevation of 720 m a.s.l., in 2009 (VFU A.2009.25, a male, and VFU B.2009.8, a female); they were encountered in a pond (ca. 3-4 m in diameter and about 30 cm deep) in a evergreen broadleaf forest. Several larvae were seen in this pond in July.
Vietnamese populations of T. asperrimus in Hoa Binh and Lao Cai Provinces (Văn Bàn District), and probably in Yen Bai Province as well, correspond to Clade C and are all located in northwestern Vietnam, through the southern Fansipan range, 600 km from the type locality Dayaoshan (Clade A) and about 300 km from Baise (Clade B). They are likewise situated in mountainous areas at moderate elevations. The Vietnamese localities are the southernmost ones known in the T. asperrimus complex.
Habitat, ethology and ecologyVery difficult to observe in its natural settings, this black crocodile newt has secretive habits. It is mainly terrestrial and lives under dead leaves or in root holes near water bodies in heavily shaded montane forests (ZHAO 1998). It feeds on various insects and their larvae, earthworms, gastropods, spiders, slugs and other small invertebrates (ZHAO 1998). In the Dayaoshan National Nature Reserve, it inhabits subtropical evergreen broadleaf forest, deciduous broadleaf mixed forest, and shrubbery where the canopy cover may exceed 75% coverage in some areas in the mountains at 1,320 to 1,400 m a.s.l. Here, it occurs near ponds at and in forests on hills with vegetation dominated by Castanopsis carlesii, C. eyrie, C. lamontii, Shima superba, Sloanea sinensis, and Gamblea pseudoevodiifolia. Its larval development plays out in ponds and small muddy pools with acidic rainwater. Andrias davidianus (Longan Cun in Dishui) and Pachytriton brevipes were recorded at higher elevations in rocky streams in the same mountain range (pers. obs.). In the Melun Nature Reserve, 1725 specimens were observed during a field survey in 2010 by QIN et al. (2012). This study also shed light on the ecological preferences of this species, revealing that it inhabits evergreen and deciduous broadleaf mixed forests composed of Itoa orientalis, Brassaiopsis glomerulata, Bridelia fordii, Cryptocarya microcarpa, Kmeria septentrionalis, Eurycorymbus calvacrici, Prunus phaeosticta, Sterculia lanceolata, Maesa japonica, Clausena excavate, Buxus latistyla, Murraya exotica, Selaginella uncinata, Epipremnum pinnatum, Alocasia macrorrhyza, Pilea longicaulis, Bulbophyllum andersonii, Nephrolepis auriculata, Elatostema sublineare, and Metabriggsia ovalifovia at elevations from 300 to 850 meters in hilly areas with spring pools 0.2 to 1.1 m deep where the temperature range is 15.0 to 18.0 °C and human activities take place.
ReproductionReproduction takes place in small temporary ponds within stands of bamboo and primary forests, triggered in April- May by rains and rising humidity values. The males will enter the water first. Courtship and mating have not yet been observed. Females deposit their 30 to 52 eggs under dead leaves on the sloped banks of a breeding pond in the manner of Echinotriton chinhaiensis (YE et al. 1993, XIE 1999, NGUYEN QUANG TRUONG pers. comm. 2015). They measure 3.0 - 3.4 mm in diameter within a gelatinous envelope that will swell to some 10 mm after absorbing water to capacity (YE et al. 1993, ZHAO 1998, XIE 1999). The aquatic larval development takes 2.5 to 3 months, during which period the larvae feed on small insects.
Status, threats and conservationAccording to the IUCN (2014), the major threat to this and all other species of the genus in China is their exploitation for traditional Chinese medicine. My observations suggest that habitat loss, degradation arising from agriculture, collection of wood, poaching for the pet trade, tourism (construction of roads), and electro-fishing are the most important threats today. As of 2015, this species was one of the most threatened species of crocodile newt in China and listed as Class-II protected under China's wildlife protection law. In Dayaoshan, rangers are trained to effectively manage, patrol and monitor reserves, develop ecotourism, and deter local people from collecting these newts for traditional medicine.
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Citation: AmphibiaWeb. 2021. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 14 May 2021.
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