Himalayan Newt, Red Knobby Newt
Species Description: Nussbaum, R. A., Brodie, Jr., E. D., Yang, D. 1995. A Taxonomic Review of Tylototriton verrucosus Anderson (Amphibia: Caudata: Salamandridae). Herpetologica, 51(3): pp. 257-268.
© 1999 Henk Wallays (1 of 54)
Author: Axel Hernandez
Tylototriton verrucosus ANDERSON 1871
Diagnosis and taxonomyThe Western Himalayan crocodile newt is a primitive species with fossils dating back to the Miocene (13 - 25 Mya) from Europe (i.e., Switzerland) that suggest a vast prehistorical range (ANDERSON 1871). The current taxonomy of the "true" Tylototriton verrucosus is problematic. Because ANDERSON (1871) neither designated a type series nor mentioned the deposition of the specimens upon which the description of T. verrucosus was based, NUSSBAUM et al. (1995) designated a neotype (KIZ 74II0061 VI.6.) from Gongwa Village (10 km from Husa (Hotha) township), 1,600 m a.s.l., Longchuan County, Yunnan Province, China, because the presumed syntypes of ANDERSON’s were attributable to T. shanjing and did not correspond to his original description of the brown-colored type.
T. verrucosus and T. shanjing occur in parapatry in Yunnan (NUSSBAUM et al. 1995), yet share mitochondrial genomes (ZHANG et al. 2007), presumably from past introgression (PHIMMACHAK et al. 2015, HERNANDEZ 2016b). Three major groups are distributed in China (see T. shanjing). T. verrucosus occurs in southwestern Yunnan Province (southwestern reaches of the Gaoligong Mountains), in the Liuku-in Luxi area (to the west of the Nujiang River), and in the north-central Ailao mountain range. It appears that divergence of this kind would follow river valleys, as rivers such as Teesta, Brahmaputra and Honghe separate populations on mountains of the Himalayas and the Hengduan mountain range from those in Indochina and southern China to the Gulf of Tonkin. Thus, there are several populations in the northern parts (Nepal, Bhutan, India) that form the Clade C of the supraspecies verrucosus. For example, types from Laos, Myanmar, Thailand or Vietnam were formerly considered relict populations of T. verrucosus before molecular and morphological studies identified them as distinct species (T. uyenoi, T. panhai from Thailand, T. shanorum from Myanmar, T. anguliceps from Vietnam, and T. podichthys from Laos), and a recent study clarified the origin of the Yunnan populations (YU et al. 2013).
The Western Himalayan crocodile newt is diagnosed by the following characters: max. 16.5 cm TL; females are larger in size and have a distinctly rounded belly whereas males are smaller and have a slim to thin appearance and a protuberant cloaca (especially during the breeding period). This species furthermore exhibits vomerine teeth in two continuous series that run parallel anteriorly and diverge posteriorly, and a blunt-tipped, oval head with a flattened crown and depressed frontal and interorbital areas. The sides of the head are distinctly bony, and the glandular areas are elevated to the level of the upper eyelid. Viewed from above, the body sports two longitudinal series of 12 - 15 dorsolateral glandular warts. The tail is compressed laterally and bears a well-developed fin. The skin is finely granular. The ground color is dark brown above, and the glands on the neck and in the dorsolateral regions are lighter brown to reddish orange (especially during the breeding season). Ventrally, the chin, belly and ventrolateral regions are brown whereas the tail, fingers and toes are lighter brown to orange.
No subspecies of T. verrucosus are currently recognized, but some intermediate populations are known (see also T. shanjing). For example, the Sagaing type from Myanmar is known to be related to the nominotypical T. verrucosus, but a better understanding of its distribution in Myanmar and Yunnan Province is needed to infer the biogeography within this species.
DistributionT. verrucosus is distributed all along the western Gaoligong mountain range from Nujiang Autonomous Prefecture (Lushui County [Pianma Town]) via the western parts of Baoshan Prefecture (Baoshan and Tengchong [Teng-yue-chow, Momien] Counties), and south to the Dehong Autonomous Prefecture (Longchuan [Husa (Hotha) Town and Gongwa] and Yingjiang Counties) (FEI et al. 2006, 2012, HOU et al. 2012, HERNANDEZ 2016b). ANDERSON (1871) did not specify an exact type locality, but merely mentioned some localities/areas (=valleys and counties) located along the Gaoligong Mountains, including the Nantin, Momien, Hotha, Ponsee and Nampoung valleys in the west of Yunnan Province. SCLATER (1892) subsequently considered specimens ZSIC 10397, 11396, 10366–81 to be syntypes of the holotype BMNH 18220.127.116.11 (FEI, HU, YE & HUANG 2006). NUSSBAUM et al. (1995) discussed some localities mentioned by ANDERSON (1871) and confirmed its occurrence in the Nantin, Momien, and Hotha valleys in western Yunnan. Nantin and Momien (Momien is one of the former Chinese Shan States) are problematic, though, because T. shanjing-type newts occur in these areas (HOU et al. 2012), and intermediate populations from hybridization could exist, as is the case with the Baoshan population (in Teng-yue-chow, Tengchong County, Momien) that is genetically close to the T. verrucosus neotype while its morphological characters are similar to the more robust T. shanjing type with well-developed costal warts (KHATIWADA et al. 2015). The two species also occur in Nantin and their delimitation is unclear there as well (NUSSBAUM et al. 1995). Thus, most of these populations attributed in the past to T. verrucosus stricto sensu are not valid to this date and could be reevaluated later with T. shanjing. A comprehensive comparative study of molecular traits is required to provide clarity on the specific identities (T. verrucosus or T. shanjing) of the populations in most of the northern areas mentioned above. Until such information becomes available, it is suggested that only localities where typical T. verrucosus occur are regarded as harboring this species: in the southwestern parts of the range in Longchuan County including Husa (Hotha) and Gongwa Townships, in Dehong Prefecture, Yunnan Province, China, and probably neighboring portions of Myanmar.
Habitat, ethology and ecologyT. verrucosus is found from 1,350 to 2,000 m a.s.l. near streams and ponds in dense primary and secondary forests and open areas. In China, some populations were found at 950 - 1,800 meters in dense primary and secondary forests and open areas near human habitations (pers. obs.). Adults are terrestrial to semi-fossorial, sheltering under rocks or logs and within leaf litter for most of the year. They have an unspecialized diet, and mainly feed on aquatic insects like dytiscid beetles, gastropods and bivalved mollusks (Sphaerium indicum, Corbicula fluminea), snails, decapod crustaceans (land crabs, Potamon potamiscus sikkimense), lumbricid and megascolecid earthworms, larvae and pupae of Diptera and Coleoptera, and nymphs of Odonata, but also on the tadpoles of anurans and even the eggs concealed in the foam nests of rhacophorid frogs (MIAN HOU pers. obs. 2016 in Chinese specimens). The larvae are bottom feeders and mainly predate on bacteria, protozoa, diatoms and zooplankton during the initial developmental stages and on chironomid larvae, tubificid worms, soil nematodes, and mosquito larvae later (DASGUPTA 1983, 1996, KUZMIN et al. 1994, DEVI 2005).
BRODIE (1984) reviewed the defensive mechanisms in salamanders and presumed that the orange coloration in this species was aposematic because the glandular excretions were noxious and toxic (see also STEBBINS & COHEN 1995). The positioning of the blunt-tipped ribs below the overlying glands is supposed to serve a defensive purpose in that they can exert pressure on the poison glands from below when the animal is disturbed, or the force of a predator’s grip/bite might press the glands against the tips of the ribs and so induce the excretion of poison. Natural predators of adult specimens include the snake-headed fishes Channa burmanica or C. gachua. Cannibalistic tendencies have also been reported. Some individuals have been recorded as living in laboratories for more than 25 years, whereas their average life expectancy is only 10 to 15 years in the wild.
ReproductionT. verrucosus breeds in large ponds, ditches and sometimes in artificial water bodies after the first heavy monsoon rains from March, April and May through September. Breeding was observed in rainwater ponds of about 30 cm in depth around Nantin, China. The water here was crystal clear (as is common in T. himalayanus of Clade C) or muddy (as is common in T. verrucosus of Clade A) with temperatures ranging from 15 - 21.0°C. These pools were surrounded by grass and located near rice paddies and other agricultural lands at an elevation of around 1,650 m a.s.l.
The adults will make synchronized migrations to their local breeding sites and intraspecific interactions, motivated both by territoriality and courtship, can be observed then, including raising the body off the ground, lowering the head, circling, and even biting (MATHIS et al. 1995). Courtship displays are similar to those known from Pleurodeles and other species of Tylototriton (CHANG 1936). Mating follows a fairly extended courtship in the water, with the female taking in pheromones released by the male, attracting the male by her movements, making him follow her, letting him stop her by positioning himself before her, and conducting a face-to- face roundabout dance. The male will eventually take hold of the female by wrapping his arms around hers from below prior to depositing spermatophores, as is typical of many salamandrids (CHANG 1936, THORN 1968). This procedure is repeated several times. Some days after the amplexus, the female will deposit her eggs on submerged vegetation and the bottom of the breeding pond, rarely outside the water. Subsequent maternal care has been observed. The eggs measure less than 2.5 mm in diameter (ZHAO et al. 1988) and will typically be deposited one by one or in pairs (ZHAO et al. 1988, NUSSBAUM & BRODIE 1982). The larvae have well-developed balancers (NUSSBAUM & BRODIE 1982).
In captivity, courtship and mating takes place from March to April. An average clutch contains some 30 eggs, even though large females may produce as many as 100. The eggs are deposited one by one on waterweed or Java moss and, measuring hardly 2.5 mm. It is best to remove them with their plants just before the embryos hatch and transfer them to a separate tank. The percentage of unfertilized eggs is high in this species. A separate tank is needed for incubating the eggs and then for raising the larvae. It should offer the same water quality and temperature as for the adults. The bottom of the larva tank is covered with small round pebbles between which the young larvae can hide, and Java moss placed in the middle of the tray will oxygenate the water naturally; a water depth of 5 cm is sufficient. At a temperature between 17.0 and 20.0 °C, the larvae hatch after 3 to 4 weeks. They will measure 15 mm in total length (TL), are beige in coloration dorsally and have black eyes. Initially, they will feed on mosquito larvae. A little later they can also handle bloodworms and Tubifex in addition to these. Their water needs to be exchanged at regular intervals. There should be enough food for all larvae, otherwise they will tend to attack each other. Only 4 - 6 larvae must be kept per tank, at a fairly low temperature of between 17 - 18.0 °C in order to let them grow for as long as possible. This is necessary because the transition from an aquatic to a terrestrial lifestyle is quite tricky and larval mortality is high. Metamorphs resemble the adults and have light brown legs, parotoid glands, tails and heads. Their costal nodes are visible as small dots aligned along either side of the body. After spending the period of metamorphosis on the banks, half in the water, half on land, the juveniles will eventually return to the water and stay there. They can now be fed with whole bloodworms (Chironomus plumosus), and will reach sexual maturity within three to four years (DEUTI & HEGDE 2007).
Status, threats and conservationThe status of individual populations differs geographically, with some being highly threatened by anthropogenic activities such as agriculture (mainly rice and tea), as is currently the situation in China. The species is classified as “Least Concern” (IUCN 2011) due to its purportedly vast geographical distribution. This could change drastically if a comprehensive review revealed this taxon to actually comprise several distinct taxa. Also, many Chinese populations have limited ranges and their trends need to be re-assessed individually.
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Citation: AmphibiaWeb. 2020. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 10 Jul 2020.
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