Tylototriton asperrimus Unterstein, 1930
According to IUCN (2010), the major threat to this species in China is harvesting for use in traditional Chinese medicine. Habitat loss and degradation arise from agricultural practices and collection of wood is also a threat. It is listed as a class II protected species under China's wild animal protection law. However, recent occurrence of large numbers of this species in the Guangzhou pet market suggests that illegal collection for the pet trade forms a new threat (Wu, Y. pers. comm.).
This species is almost uniformly grayish black; orange red only at digit tips, cloaca and underside of tail. In some individuals from the type locality the first dorsolateral warts have orange coloration (Wu, Y., pers. comm.). Bony ridges prominent on head. 13–16 dorsolateral warts on each side. Separation between warts is clear (Fei et al., 2006).
2n=24, 1M, 2M, 3M, 4M, 5M, 6SM, 7M, 8SM, 9M, 10M, 11M, 12ST, from Gu and Gao (1996).
M: metacentric; SM: submetacentric; T: telocentric; ST: subtelocentric
The mitochondrial genome has been sequenced by Zhang et al. (2008).
This species resembles Tylototriton wenxianensis and T. hainanensis, but differs from T. wenxianensis by clearly separated large dorsolateral warts and from T. hainanensis by a relatively narrower head and smaller body size.
Medium-sized Tylototriton. Head flat and oval, with prominent bony ridges. Head width slightly larger than head length. Rounded snout. No labial fold. Gular fold conspicuous. Body slender and flattened. When limbs are adpressed, digits meet or slightly overlap. Dorsal ridge distinct but low and segmented; dorsolateral warts prominent. Skin rough, with fine granules. Small transverse wrinkles present on venter. Tail compressed laterally and ending in a pointed tip. Tail shorter than snout-vent length (Zhao, 1998). Males have a longer cloaca, as long as the distance between nostrils. Small papillae present in males’ cloaca. Cloaca of females is much shorter and swollen during breeding season (Fei et al., 2006). Tylototriton asperrimus is uniformly grayish black; orange red only at digit tips, cloaca and underside of tail. Some individuals from the type locality have a few orange tinted dorsolateral warts (Yunke Wu, pers. observ.).
All measurements are from Fei et al. (2006).
Male (20 specimens). Snout-vent length: 60.5–72 mm; Tail length: 54–71.7 mm; head length: 13.5–16.7 mm; head width: 15–17.9 mm; forelimb length: 17.6–21 mm; hind-limb length: 18.6–22.2 mm.
Tylototriton asperrimus shares some external characters with Echinotriton, such as pointed ribs piercing the skin, and reproductive habits, such as laying large eggs on land. This species was placed in Echinotriton by some authors (Zhao and Hu, 1988). But recent genetic work suggests that T. asperrimus is better placed in Tylototriton (Larson et al., 2003; Weisrock et al., 2006; Zhang et al., 2008).
The relationships among Tylototriton asperrimus, T. wenxianensis, T. hainanensis, T. vietnamensis and T. notialis are unclear due to a high degree of morphological similarities. Recent molecular work based on mitochondrial and nuclear sequence data revealed moderate to large genetic divergence among these four species, which form a monophyletic group (Weisrock et al., 2006; Stuart et al., 2010). Tylototriton asperrimus and T. wenxianensis are sister species, whereas T. hainanensis and T. notialis could be sister species. Tylototriton vietnamensis is the sister lineage to the other four species.
The species is widely distributed in southern China at altitudes of 400 to 1,700 m. It also occurs in northern Vietnam. Besides T. asperrimus, two more species are known from Vietnam, T. vietnamensis (Böhme et al., 2005) and T. verrucosus (Nguyen et al., 2009). Populations from central China were initially described as a subspecies and later elevated to a full species, namely T. wenxianensis (Fei et al., 1984; Fei et al., 1990). Populations from central Laos were described as T. notialis (Stuart et al., 2010).
Tylototriton asperrimus lives under dead leaves or root holes near water in heavily shaded forest in the mountains (Zhao, 1998). For reproduction small temporary ponds are used in bamboo and primary forest (IUCN, 2010). Outside the breeding season, the species lives on land, where it feeds on insects and their larvae, earthworms, spiders, slugs and other small invertebrates (Zhao, 1998).
Breeding season in April-May. Males enter the water, but reproductive behavior has not yet been observed. Females lay egg clutches on land under dead leaves as do Echinotriton chinhaiensis (Ye et al., 1993; Xie, 1999; Bain & Nguyen, 2004). Clutches of 30 to 52 eggs are laid on the slopes of a breeding pond, under dead leaves. Egg diameter 3.0-3.4 mm, diameter of gelatinous envelope after fully absorbing water is 10 mm (Ye et al., 1993; Zhao, 1998; Xie, 1999). Larvae develop in water.