Hynobius leechii Boulenger, 1887
This salamander is abundant and relatively wide-spread, listed as of least concern in the IUCN Red List of Threatened Species (IUCN, 2010). But habitat destruction is a threat to populations in China (Zhao, 1998).
The overall size is small, around 110 mm. Labial fold absent. Irregular dark spots present on dorsum and tail. 11–13 costal grooves, rarely 14. Dorsal caudal fin present. Tubercles prominent on palms and soles (Fei et al., 2006).
Karyotype:
2n=56, 1M, 2M, 3M, 4ST, 5M, 6M, 7SM, 8SM, 9M, 10SM, 11SM, 12SM, 13M, 14M, 15M, 16M, 17M, 18M, 19M, m (20–28), from Zeng et al. (1997).
M: metacentric; SM: submetacentric; T: telocentric; ST: subtelocentric; m: micro-chromosome
The mitochondrial genome has been sequenced by Zhang et al. (2006). Allozyme data are available from Zeng & Fu (2004).
Small salamander. Tail shorter than snout-vent length. Head a little longer than wide, slightly depressed; snout short and round, big eyes. Vomerine teeth (31–36) in V-shaped pattern. Gular fold present. Body almost cylindrical, with 11–12 costal grooves (Litvinchuk & Borkin, 2003). Fei et al. (2006) note 11–13 (rarely 14) costal grooves. Limbs of moderate length, fingers and toes not meeting when fore- and hindlegs are laid along the body. Base of tail cylindrical, gradually compressed toward the tip and ending in an obtuse tip. During the breeding season the female can be recognized by the swollen abdomen and cloaca (Kang & Yoon, 1975; Park & Park, 2000), the male has a higher tail fin and swollen cloaca (Kim et al., 2009). Females have shorter legs than males; in juveniles legs are proportionately longer (Dunn, 1923). Color olive brown to blackish-brown above, mottled with irregular gray-brown spots; tail grayish brown with some dark spotting. Light gray below. Juveniles speckled with small light-colored spots. Total length 9 to 14 cm (Zhao, 1998) but more usually 11–12 cm; the female is a little larger than the male (Park et al., 1996).
All measurements are from Fei et al. (2006).
Male (3 specimens). Total length: 85–105 mm; snout-vent length: 48–60 mm; Head length: 13–14.5 mm; Head width: 8–9 mm.
Female (3 specimens). Total length: 90–110 mm; snout-vent length: 58–62 mm; Head length: 13–14.5 mm; Head width: 9.5–10 mm.
Hynobius mantchuricus, a species described from Xiongyue county of Liaoning, is considered a synonym of H. leechii because specimens from Xiongyue show no difference to H. leechii from northern China in both morphological and genetic characters (Zeng & Fu, 2004). Genetic diversity is very low in Chinese populations, which is in strong contrast to the high diversity in Korean populations (Yang et al., 1997; Lee et al., 1998). Within the genus, H. leechii is closest related to Korean and some Japanese species, not to other Chinese species from central to southern China (Nishikawa et al., 2010).
The species ranges from northeastern China (Liaoning, Jilin, Heilongjiang; Fei et al., 2006) southward to North and South Korea. Southern limits of range are in the south of South Korea, where it is replaced by H. quelpaertensis in the SW coastal zones and by H. yangi at the SE coast (Kim, 2009).
Outside the breeding season, this salamander is found under rotten leaves, stones or logs near streams or ponds at elevations of 200–850 mm. It is mostly nocturnal but is active during rain. It feeds on insects, snails, slugs and earthworms. Hibernation takes place under thick rotten leaves, watery soft soil or stones. In the breeding season, adults gather in lentic ponds covered by forest canopy. Visibility is low. There are thick rotten leaves and abundant twigs in the pond (Ma et al., 2003).
In China the animals enter the water in the beginning of April when water temperatures are 2–5℃. The breeding season extends from mid April to mid May when water temperatures range from 4–12℃ (Liu et al., 1984). In South Korea the animals may enter the water earlier, late February, and the breeding season lasts from early March to early April. Males arrive at a breeding site two to three days earlier than females and stay there for approximately ten days (Sung et al., 2005; Lee & Park, 2008). Males outnumber the females present in the water. This male-biased operational sex ratio implies a fierce competition among males to monopolize and fertilize the eggs. In general, three to four males simultaneously mate with a single female. As a result multiple fertilizations of egg sacs of one female occur, with the competing males scrambling over the egg sacs (Park & Park, 2000; Kim et al., 2009). Sexual behavior consists of three stages: identification, courtship and fertilization. The male identifies the female by sniffing and making snout contact. He courts the female with several behavior patterns, involving rubbing his chin against the female’s head, undulating his body and tail, sniffing and so-called digging displays, during which the male moves under the female’s body using his head and forelimbs. Shortly before the egg sacs appear, the male clasps the female’s back with fore and hind limbs. He may then free his fore legs from the female, while keeping his hind legs positioned near the female’s cloaca; he grabs the egg sacs with his fore legs and chin, and pulls them out of the female’s body. When the eggs are separated from the female, the male wraps his body around the egg sacs, held between his forelimbs, mouth and hind limbs; he scratches the eggs with his hind feet and releases his sperm over the eggs (Park et al., 1996). After fertilization the male may keep his body wrapped round the eggs for some time, and do so repeatedly, a posture interpreted as egg guarding behavior (Park & Park, 2000). When two males meet, this encounter may end in moving away of one of the two, or in one animal biting the other in the chin and shaking his neck (Park et al., 1996). Hynobius leechii shows two different types of vibration signals, a body undulation for mating display to the female or male (Kim et al., 2009) and a tail undulation for aggressive display to rival males. Males often display this behavior, during which only the distal part of the tail waves, before and after attacking other males (Park et al., 2008).
The female produces a pair of egg sacs, containing 57-125 eggs. When fully hydrated, the egg sacs reach 12-14 cm in length and 12 mm in width. Egg sacs are attached to stones or twigs under water in streams, ponds and rice fields. Fertilized eggs normally hatch within three to four weeks and larvae have an aquatic period of one to two years (Park & Park, 2000). Zhao (1998) and Liu et al. (1984), however record a hatching time of 10-16 days, due to keeping them at higher temperatures in the laboratory. Upon hatching larvae measure 12-13 mm and have three pairs of external gills and well-developed balancers. When the larva starts swimming the dorsal fin takes about two thirds of the back, starting from the level where the gills end. At a length of 30-35 mm the balancers disappear. Metamorphosis takes place at a length of approximately 40 mm, and life on land begins (Liu et al., 1984).Larvae feed on small aquatic invertebrates and, like many salamander species, also cannibalize on amphibian larvae, including conspecific larvae. Foraging experiments have shown that cannibalistic larvae discriminate siblings from non-siblings and that small siblings are more vulnerable to cannibalism by large siblings than large ones (Park et al., 2005).