AmphibiaChina 中国两栖类.

Description
Paramesotriton hongkongensis is a relatively large, stocky newt. Males are smaller than females with a snout-vent length range of 62 – 68 mm and a total length of 104 - 124 mm, while females have a snout-vent length range of 60.0 - 77 .7 mm and a total length of 118 – 143 mm (Fei et al. 2006). Its flattened head is equal or slightly longer than it is wide, and it has a truncated snout. No maxillary teeth are present, but a single upside down “V” shaped vomerine tooth is present (CITES 2016). A cranial ridge runs from the tip of the snout to the parotid region and it has a bony median parietal ridge. The skin of the head and dorsum is thickly covered with low granular tubercles. Large warts occur in distinct dorsolateral ridges along the back, and a vertebral ridge is present (Myers and Leviton 1962, Sparreboom 2014). No costal grooves are present. The limbs are relatively long with unwebbed fingers and toes (Myers and Leviton 1962, CITES 2016). The hind limbs are slightly longer than the forelimbs (Fei et al. 2006) and overlap when adpressed along the body (CITES 2016). Its head-body length is longer than the tail, which is laterally compressed with a blunt tip (Myers and Leviton 1962, CITES 2016). Tails average 73% and 89% of snout-vent length in males and females respectively (Fu et al. 2013, CITES 2016).

Formerly considered a subspecies of Paramesotriton chinensis, P. hongkongensis can be differentiated by having smoother, tuberculated skin rather than warty skin, shorter and more clustered parasphenoid teeth, a broader head and interorbital region, a conspicuous median parietal ridge, stronger dorsolateral ridges, large orange to red spots in the gular region, and a continuous orange to red line along the ventral midline of the tail (Myers and Leviton 1961). Additionally, the more pronounced ridges of P. hongkongensis gives the body a more geometric shape and the tail is shorter and slightly taller (CITES 2016). In general, P. hongkongensis is larger and more robust (Zhang et al. 2011). Lastly, the two species also have different breeding seasons; P. hongkongensis breeds from November to February while P. chinensis breeds from May to June (Sparreboom 2014).

In life, P. hongkongensis adults are uniformly dark brown or black to olive green dorsally, except for the orange to red vertebral ridge, which varies in intensity. Ventrally, they are bluish-black with irregular orange to red splotching from the chin to the vent. This pattern is unique to each individual and can be used to identify specific individuals. Ventral patterning differs between the sexes with males having fewer, larger splotches against a lighter blue gray background, whereas females have smaller splotches against a more uniformly black stomach. Males always have a large orange to red patch just before the cloacal opening, whereas females do not. During the breeding season males have a swollen cloaca and a light whitish blue stripe along the tail (Romer 1951, Myer and Leviton 1962, Fu et al. 2013, Sparreboom 2014). The laterally flattened tail has a thin orange to red stripe along the ventral midline that fades towards the tip (Myer and Leviton 1962, Karsen et al. 1998).

In preservative, the dorsum of adults is uniformly brown with mottled yellow spots on the lateral surfaces. The throat and ventrum are dark brown with large yellowish blotches and yellow lines along the mandible and ventral midline of the tail (Myers and Leviton 1962).

There is sexual dimorphism in this species with females having a larger snout-vent length than males and males having a longer head and shorter tails than females (Romer 1951). Males also have a orange patch before the cloacal opening (Sparreboom 2014). Individuals found in intact forests are larger than those in disturbed forests (Fu 2010).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: China, Hong Kong

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (1 records).

This species is only found in coastal areas of Guangdong Province and the Hong Kong Special Administrative Region in China. In Guangdong the species is found in the vicinity of Shenzhen, Longmen, Dongguan, Conghua, and Zengcheng. In the Hong Kong Special Administrative Region the species can be found in isolated populations on the slopes of Tai Mo Shan of the mainland, Hong Kong Island, and Lantau Island, (Zhang et al. 2011, Fu et al. 2013, Sparreboom 2014, CITES 2016). The total distribution of the species is only 20,000 square kilometers (Lau and Chan 2004, CITES 2016).

The newts occur at elevations between 0 m and 940 m, breeding in slow moving, clear streams and deep pools with aquatic vegetation, plenty of rocks for cover, and some hanging vegetation (Karsen et al. 1998, Lau and Chan 2004, Fu et al. 2013, CITES 2016). Adults spend the wet season in the terrestrial habits surrounding these aquatic environments, preferring forested areas to grasslands (Fu et al. 2013).

Life History, Abundance, Activity, and Special Behaviors
Paramesotriton hongkongensis is predominantly nocturnal and alternates between terrestrial and freshwater environments. The non-reproductive phase is spent in terrestrial environments while during the reproductive phase individuals return to water to breed and lay eggs. Once they return to their aquatic phase, adults can be found on rocks at the bottom of streams or along riversides (CITES 2016). Despite early reports by Romer (1951), the time spent in aquatic habitats for reproductive purposes is only about 45 days (Fu et al. 2013, Sparreboom 2014), which indicates that these newts inhabit terrestrial areas, thought to be in crevices or under rocks with abundant vegetation, for almost 10 months out of the year (Fu et al. 2013, CITES 2016).

Paramesotriton hongkongensis migrate to pools to breed during the dry season in November to February. Dry season breeding is atypical for amphibians in this region, and this behavior reproductively isolates the species from the closely related P. chinensis (Sparreboom 2014). A dry breeding season also decreases the availability of breeding pools, therefore causing males to be more aggressive and bite conspecifics. The cue for reproduction may be dependent the amount of rainfall and temperature (Fu et al. 2013).

Reproductive behavior is initiated when the male tenuously approaching the female. If she allows him to get close, he will start gently nudging his snout against the female’s body. Following this the male will dash alongside the female, stop in front of her head, and begin a lateral, fanning display with his tail, which has developed a white or bluish marking. If amenable to his advances, the female moves forward to lightly nudge the male’s cheek or back. The male then responds by completely turning away from her to present his tail. At this point he will wag his tail in a “S” shape in front of the female's snout. To show her interest, the female uses her snout to nuzzle the male’s tail, which prompts the male to inch forward in order to drop a spermatophore. If she is receptive to fertilization, the female will follow the male and move forward to collect the spermatophore with her cloaca (Arnold 1972, Fu et al. 2013, Sparreboom 2014, CITES 2016).

The female will deposit her egg between February and March by adhesively securing her clutch to submerged vegetation or leaves near the edges of pools (Karsen et al. 1998). Eggs are laid singly or in a series. While this is happening, the female uses her hind legs to press the leaves of aquatic plants around the eggs so that all her eggs are secured in the same leave patch (Sparreboom 2014). In the lab, one female laid eggs over the course of three weeks (Romer 1951). In general, the average clutch of eggs is approximately 115 - 120 small eggs, which are characterized as pale grey, gelatinous, and oval (Karsen et al. 1998). In terms of size, P. hongkongensis eggs exceed those of most other salamander species. Each egg is about 2.9 mm in diameter, with an enclosing jelly capsule that is 6 x 4.5 mm (Romer 1951, Kong and Tong 1986, Sparreboom 2014). The upper hemisphere of the egg is brown and the lower is a pale, whitish color (Romer 1951).

After deposition it takes 3 to 6 weeks before eggs hatch into their aquatic environment with a total length of 10 – 14 mm (Kong and Tong 1986). No form of parental attendance is documented for this species (Fu et al. 2013). The larvae spend about 7 ½ months after hatching in the water before beginning metamorphosis (Fu et al. 2013, Sparreboom 2014) but may overwinter as larvae (Romer 1951). At this point gills recede as larvae move onto land. Within 1 year, they metamorphose and in 2 – 4 more years, they sexually mature (Fu et al. 2013, Sparreboom 2014, CITES 2016). The species’ total life span is thought to be around 10 years (Fu et al. 2013, CITES 2016).

The species is a generalist predator that exhibits cannibalism. Adults primarily consume shrimp and snails, but also consume insects, earthworms, tadpoles, fish fry, shed skin, and plant fragments. Adult males show a preference for large food items while adult females are more likely to be cannibalistic on larvae and eggs than adult males. Larvae are carnivorous and also exhibit cannibalism, eating both eggs and other larvae (Fu et al. 2013, Sparreboom 2014).

Both adults and eggs of P. hongkongensis contain toxins but are not deadly to humans (Brodie et al. 1974). Despite this, the species may also feign death when threatened by predators (CITES 2016).

Larva
Larvae measure 10 -14 mm in total length when they hatch, and 40 - 44 mm in total length when they metamorphose to their terrestrial form. The depressed head is longer than broad with a blunt snout and feathery external gills. The distance between the eyes is greater than the distance from the eye to the snout tip. The body is horizontally compressed and the tail is pointed. The dorsal fin of the tail starts on the dorsum and the ventral fin begins at the vent (Romer 1951, Sparreboom 2014).

In life, larvae are black dorsally with lighter colored tails and unpigmented margins on the dorsal fin. There is a white to yellow spot on the snout between their nostrils. The bellies are black and have sporadic pale yellow speckles. The ventral surfaces of the head and limbs are paler and the ventral surfaces of the limbs have traces of yellow. The ventral surface of the tail fin closes to the body has pale yellow coloration. The gills are pink with black patches closer to the base of the gills. The irises are golden with a horizontal black bar through the center of both the iris and pupil (Romer 1951, Sparreboom 2014).

Trends and Threats
Despite being a common species in their range, populations of P. hongkongensis are declining. The species is listed as “Near Threatened” on the IUCN Red List of Threatened Species and is close to qualifying for “Vulnerable” status (Lau and Chan 2004, CITES 2016). The main threats to the species are illegal harvesting of individuals for the pet trade and habitat loss and degradation (Lau and Chan 2004, Fu et al. 2013, CITES 2016).

Although the species is protected under local statutes, regulations are rarely enforced and illegal collection is still rampant, especially in mainland China. Harvested individuals are usually breeding adults, depleting the parent stock and leading to even sharper declines (CITES 2016). This species can be bred in captivity (Lau and Chan 2004).

Although the species can be found in many protected areas on both the mainland and the island of Hong Kong, within those areas increases in tourism have led to localized extinctions due to pollution and channelization of streams. In areas that are not protected, hydropower and other developments have destroyed and degraded natural habitats and increased water pollution (CITES 2016).

Asian salamanders in the pet trade have been linked to the lethal chytrid fungus, Batrachochytrium salamandrivorans (Bsal), outbreak in Europe. On January 13, 2016, P. hongkongensis was listed as one of 201 salamander species banned from import to the United States of America due to fears of the spread of Bsal. In the fall of 2016, CITES (Convention of International trade in Endangered Species of Wild Fauna and Flora) proposed listing the species as Appendix II to lessen illegal collection of the species and mitigate Bsal risk (CITES 2016).

Relation to Humans
Paramesotriton hongkongensis is collected for pet trade and traditional Chinese medicine (Fu et al. 2013, CITES 2016). The species can also be bred in captivity (Lau and Chan 2004).

Possible reasons for amphibian decline

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

Comments
Bayesian Inference of ND2, tRNA^Trp, and tRNA^Ala mtDNA sequences indicate that P. hongkongensis is sister to the clade composed of P. chinensis and P. qixilingensis. Together, these three species are sister to a clade composed of P. deloustali, P. fuzhongensis, P. guangxiensis and P. yunwuensis. However, these relationships are poorly supported (Yuan et al. 2014).

A larger Bayesian analysis of the Salamandridae family using 14,461 basepairs of mtDNA, which omitted P. chinensis but included P. hongkongensis, indicate that the genus Paramesotriton is sister to the genus Cynops (Zhang et al. 2008).

AFLP analysis of two mainland Hong Kong populations of P. hongkongensis and the population at Hong Kong island indicate that the two mainland populations, separated by the highest mountain (Tai Mo Shan) in Hong Kong, are more distantly related to each other than either are from the island population. These results were surprising in that they indicate that a terrestrial barrier was more significant than a 6000 year-old marine barrier. Two explanations were proposed to explain this result: that the genetic divergence between the mainland populations occurred before the marine barrier was created, or that the rate of divergence between the mainland populations was more rapid than between the mainland and island populations (Zhang et al. 2011).

This is the only salamander found on the island of Hong Kong, hence the species epithet, “hongkongensis” (Zhang et al. 2011).

When described by Myers and Leviton (1962), the species was named Trituroides honkongensis. Shortly thereafter it was moved to the genus Paramesotriton. Despite being described as a full species, P. hongkongensis was considered a subspecies of P. chiensis between 1990 and 2009 (Frost 2019).

References

Brodie, E. D., Jr., Hensel, J. L., and Johnson, J. A. (1974). ''Toxicity of the urodele amphibians Taricha, Notophthalmus, Cynops, and Paramesotriton (Family Salamandridae).'' Copeia, 1974(2), 506-511.

CITES (2016). “Proposal for amendment of Appendix I or II.” Seventeenth meeting of the Conference of the Parties Johannesburg (South Africa), 24 September – 5 October 2016, CoP17 Prop. 41.< https://cites.org/sites/default/files/eng/cop/17/prop/060216/E-CoP17-Prop-41.pdf> Downloaded 25 June 2019

Fei, L., Hu, S.-q., Ye, C.-y., Huang, Y.-z. (2006). Fauna Sinica, Amphibia. Volume 1. General Accounts of Gymnophiona and Urodela. Chinese Academy of Sciences. Science Press, Beijing.

Frost, D. (2019). “Paramesotriton hongkongensis (Myers and Leviton, 1962).” Amphibian Species of the World. http://research.amnh.org/vz/herpetology/amphibia/Amphibia/Caudata/Salamandridae/Pleurodelinae/Paramesotriton/Paramesotriton-hongkongensis. Downloaded on 1 July 2019.

Fu, W.K., Karraker, N. E., Dudgeon, D. (2013). ''Breeding dynamics, diet, and body condition of the Hong Kong Newt (Paramesotriton hongkongensis).'' Herpetological Monographs, 27(1), 1-22. [link]

Karsen, S.J., Lau, W.-N. M., Bogadek, A. (1998). Hong Kong Amphibians and Reptiles. Provisional Urban Council, China.

Kong, Y., Tong T. (1986). ''The developmental stages of Paramesotriton hongkongensis (Myers & Leviton).'' Acta Herpetologica Sinica, 5, 106-118.

Lau, M.W.N., Chan, B. (2004). “Paramesotriton hongkongensis”. The IUCN Red List of Threatened Species 2004: e.T59460A11945539. Downloaded in June 2019

Myers, G. T. Leviton, A. E. (1962). ''The Hong Kong Newt described as a new species.'' Occasional papers by the Division of Systematic Biology of Stanford University, 10, 1-10. [link]

Romer, J.D. (1951). ''Observations on the habits and life-history of the Chinese Newt, Cynops chinensis Gray.'' Copeia, 1951(3), 213-219. [link]

Sparreboom, M. (2014). Salamanders of the Old World: The Salamanders of Europe, Asia and Northern Africa. Zeist, Brill, The Netherlands.

Yuan, Z., Zhao, H., Jiang, K., Hou, M., He, L., Murphy, R.W., Che, J. (2014). ''Phylogenetic relationships of the genus Paramesotriton (Caudata: Salamandridae) with the description of a new species from Qixiling Nature Reserve, Jiangxi, southeastern China and a key to the species.'' Asian Herpetological Research , 5, 67-79. [link]

Zhang, P., Papenfuss, T. J., Wake, M. H., Qu, L., Wake, D. B. (2008). ''Phylogeny and biogeography of the family Salamandridae (Amphibia: Caudata) inferred from complete mitochondrial genomes.'' Molecular Phylogenetics and Evolution, 49(2), 586-597. [link]

Zhang, Y. X., He, C. Z., Dudgeon, D., Zhang, Z. Y., Wang, G. M. (2011). ''Mountain ridge and sea: Geographic-barrier effects on genetic diversity and differentiation of the Hong Kong Newt (Paramesotriton hongkongensis) revealed by AFLP.'' Annales Zoologici Fennici, 48(2), 119-127. [link]

Species Account Citation: AmphibiaWeb 2023 Paramesotriton hongkongensis: Hong Kong Warty Newt <https://amphibiaweb.org/species/5918> 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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