Tiannan Crocodile Newt, Tiannan Knobby Newt, Yang’s Crocodile Newt
Species Description: Hou M, Li P, Lu S 2012 Morphological research development of genus Tylototriton and primary confirmation of the status of four cryptic species (in Chinese). J Huangshan Univ 14:61-65. (authors of name: Hou, Zhang, Zhou, Li and Lu).
© 2014 Kai Wang (1 of 25)
The average newly hatched aquatic larvae are between 10 – 12 mm in total length (Wang et al. 2017). The head is flat with a slender labial fold (Hernandez and Hou 2018). When hatched, larvae have large eyes, small forelimb buds, and three well-developed pairs of gills (Wang et al. 2017). They have nearly invisible costal grooves (Hernandez and Hou 2018). Their tail fins are considered to be deep with the dorsal fin starting posterior to the head and taking up approximately three fourths of the total length of the larvae (Wang et al. 2017, Hernandez and Hou 2018). The ventral fin takes up one third of the total length (Wang et al. 2017). During metamorphosis, the features the larvae are born with begin to disappear and the typical morphology of Tylototriton yangi adults appear (Wang et al. 2017, Hernandez and Hou 2018).
From other members of the subgenera Liangshantriton, Tylototriton and Yaotriton, T. yangi can be differentiated due to their black pigmentation located on the head, dorsum, and venter and bright orange at the corner of their mouths, paratoids dorsolateral warts, fingers, toes, cloaca, and tail. Tylototriton yangi looks like an intermediate form of T. kweichowensis and T. shanjing, however, unlike T. kweichowensis, T. yangi has 15 - 16 distinctly separated dorsolateral glandular warts. Additionally, T. yangi is differentiated from T. shanjing by the former having a black head and limbs, as well as the formation of a large cranial ridge. In contrast to T. taliangensis and T. verrucosus, T. yangi has bright orange pigmentation on the tail and dorsolateral glands, as well as enlarged edges on their cephalic region (Hernandez and Hou 2018). In general, bright markings in T. yangi differentiate it from T. shanorum. However, the immaculate ventrum of the Mount Dawei population of T. yangi also differentiated T. shanorum from the focal species (Nishikawa et al. 2014). The black anterior half of the head differentiates T. yangi from the orange anterior head of T. anguliceps (Le et al. 2015).
In life, the background dorsal and ventral color for T. yangi generally ranges from dark to black. This coloration gets darker as they grow older. There is bright orange coloration on the corners of the mouth, parotoids, dorsolateral glandular warts, fingers, toes, tail, and the cloacal region. Tylototriton yangi has bright orange spots on the tail that expand onto the entire tail in adulthood (Hernandez and Hou 2018).
Typically, in life, T. yangi larvae have a yellowish brown dorsal surface speckled with small white dots. At hatching they also have a large, bright yellow abdominal yolk sac. The gills are light pink and somewhat translucent in color. Just before metamorphosis, larvae begin to resemble adults with a broadened head, black coloration, traces of ridges, small orange warts and a lack of gills (Wang et al. 2017). As they develop, the dorsal white spots change color gradually and become warts. Additionally, spots on the tail grow to cover the whole tail and turn bright orange (Hernandez and Hou 2018).
Tylototriton yangi have both variation by population and between sexes. Tylototriton daweishanensis from Mount Dawei Pingbian County, Honghe (Yunnan, China) is considered a junior synonym of T. yangi but can be differentiated by individuals from Daweishan having yellow to orange pigmentation on the lower sides of the fingers and toes, the cloacal region, and the ventral caudal keel. Additionally, the dorsolateral glandular warts in the Mount Dawei population are less prominent and more distinct. Another population with similar morphological characteristics to T. yangi was found along the Lao border by Axel Hernandez around 2016 (Hernandez 2016) but analysis needs to be done to determine its genetic relatedness.
Tylototriton yangi display sexual dimorphism in size where females are larger than their male counterparts. Observed females had a maximum measurement of 172 mm in length whereas males grew up to 158 mm (Hernandez and Hou 2018).
Distribution and Habitat
Life History, Abundance, Activity, and Special Behaviors
For reproduction, they prefer to be in patches of mixed forests and plantations as these provide scrubs, grasses, and small pools with ideal humidity levels. The breeding season ranges from May to August and is stimulated by high humidity and high temperatures (Hernandez and Hou 2018; Wang et al. 2017). During the breeding season in Gejiu, the relative humidity level was 86% and air temperature ranged from 20.9 - 22.4°C (Hernandez and Hou 2018). Courtship takes place in scattered permanent ponds and various bodies of stationary water. Males typically aggregate and perform courtship behaviors at acidic water sites with an average pH of 6.7 (Wang et al. 2017, Hernandez and Hou 2018). The conservation of the T. yangi species depend highly on the presence of ephemeral ponds and water canals, which typically contain high vegetation and aquatic plant life. Additionally, the water sources that T. yangi inhabit tend to contain Arthropoda and Mollusca. (Hernandez and Hou 2018). Factors of the water body such as depth, resource availability, and risks of predation affect usage of these water bodies by T. yangi (Wang et al. 2017).
During courtship, observed in both captive and wild T. yangi, the male will initiate specific behaviors to show interest in the female. After receiving the attention of a female, the male newt moves towards the female and repeatedly makes contact with his head to her head and lateral body, focusing on her orange warts. In turn, the female nudges the male back with her snout. It is unclear if newts are nudging or smelling each other during this part of the courting process. The male continues to rub against the female once she becomes more responsive towards him. The female trembles her tail when the male rubs her body with his cheek and snout. At this stage of courting, the male curls the posterior part of his body and folds his tail in an “S-shaped posture”, with the tip of his tail close to its base; he rapidly fans the dorsal part of his tail toward the female after, finishing the courting process. The displays of T. yangi’s extensive nose rubbing and nudging prior to tail fanning has been observed in other local Tylototriton but has not been observed in other species in the exotic pet-trade (Wang 2017).
Like all newts, Tylototriton transfer sperm by means of a spermatophore; it is placed on the substrate by the male and is taken up into the cloaca of the female (Houck and Arnold et. al 2003). Captive individuals under observation have shown a complete amplexus (Hernandez 2016).
Tylototriton yangi eggs are non-adhesive and are laid singularly, unlike similar species who have small clutches of adhesive eggs (Wang et al. 2017). They have a hatching period of approximately 15 days and a metamorphose period of 115 days. The larvae tend to stay in small ponds with high relative humidity and temperatures (Hernandez and Hou 2018). These ponds were noted as slow-flowing streams with high amounts of biodiversity; mollusks, fish, other tadpoles and crabs were seen in these ponds. Ephemeral water ponds and canals are crucial for survival and conservation as this is where the majority of animals were found between the months of April and September. During these months, the ponds are semi-transparent and have high concentrations of phytoplankton and zooplankton; two of the main parts of the T. yangi diet (Hernandez and Hou 2018). In captivity, the larvae were fed with live bloodworms (Wang 2017).
Tylototriton yangi are predated on by crabs and potentially by fishes, due to their cohabitation in water sites (Hernandez and Hou 2018).
Trends and Threats
Tylototriton yangi is listed as “Vulnerable” by IUCN. After the discovery of of the species in 2012, wild populations have been on a declining trend due to illegal trafficking, over-exploitation, habitat loss, and pollution. Unfortunately, T. yangi are morphologically similar and commonly mistaken with T. kweichowensis, which was the most common Tylototriton species sold in United States pet markets (Wang et al. 2017). This oversight and misclassification of the species may have contributed to unintentional capturing of T. yangi, although the Asian newt importation ban may have decreased these sales (Rowley et al. 2016). Populations affected by capture and sale for the terrarium animal trade have been relocated to novel regions in Europe, such as France, Germany, and Russia (Hernandez 2016).
From May to July, populations of adult T. yangi are harvested seasonally by locals to be dried, sold, and used for traditional medicine (Wang et al. 2017).
Other substantial threats to the species are caused by agrochemical pollutants from tin and coal mining activities, which has led to general habitat loss (Hernandez 2016). The animal is in grave danger of extinction due of its overlapping distribution with tin-mining sites in Southern China (Hernandez and Hou 2018). In addition to complete loss of habitat due to deforestation, remaining terrestrial habitats were fragmented and breeding ponds were contaminated (Wang et al 2017). The conservation of T. yangi is dependent on the presence of ephemeral ponds and water canals, which typically contain high vegetation and aquatic plant life (Hernandez and Hou 2018).
The Chinese Government has added T. yangi to its List of Endangered Species of China as a Class II nationally protected species. The government has also increased law enforcement of the Wildlife Protection Act of China during the newt’s breeding season. Restoration of natural plant communities and construction of artificial breeding ponds has also begun. As more research is being done on this species, institutions have initiated captive-breeding programs, which have also declined its wild population numbers. Since the public has increased its attention of T. yangi, conservation activity has increased significantly in hopes of restoring the species population (Wang et al. 2017).
Relation to Humans
Possible reasons for amphibian decline
General habitat alteration and loss
Bayesian Inference and Maximum Likelihood analyses of 988 bp of ND2 mtDNA sequence indicate that T. yangi is basal to the clade formed by the T. verrucosus-shanjing complex, T. uyenoi and T. anguliceps (Nishikawa et al. 2014, Le et al. 2015).
The genus name, Tylototriton was coined by John Anderson, M.D., Curator of the Indian Museum, in his paper “Description of a new genus of newts from western Yunan”. The name is derived from the Greek word “tulos” meaning “swelling” and the generic name, Triton, which refers to the Greek god of the sea (Hernandez 2016).
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Wang, K., Yuan, Z., Zhong, G., Li, G., Verrell PA. (2017). ''Reproductive biology of Tylototriton yangi (Urodela: Salamandridae), with suggestions on its conservation.'' Amphibian and Reptile Conservation, 11(2), 33-43. [link]
Written by Sean Ashley Calalang (sascalalang AT ucdavis.edu), University of California, Davis
First submitted 2019-12-05
Edited by Ann T. Chang (2019-12-09)
Species Account Citation: AmphibiaWeb 2019 Tylototriton yangi: Tiannan Crocodile Newt <http://amphibiaweb.org/species/7874> University of California, Berkeley, CA, USA. Accessed Jul 5, 2020.
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Citation: AmphibiaWeb. 2020. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 5 Jul 2020.
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