Ranodon sibiricus Kessler, 1866
The range of this species is severely fragmented and the current range is continuing to decline. Human activities, including deforestation, fishing and cattle farming pose a threat, as well as over-exploitation for scientific aims and pet trade. Existing conservation measures have to be taken more seriously to protect this vulnerable animal. It is considered critically endangered in China (Zhao, 1998; Wang & Bai, 2000) and endangered by IUCN standards. It is urgent that strict nature reserves are created to save this species from extinction (Stuart et al., 2008; IUCN, 2010).
Vomerine teeth arranged in two short, widely separated series between the internal nares. Premaxillary fontanelle small (Fei et al., 2006). Costal grooves 11–13. Tail usually a little longer than body. In adults no cornified covering on palms and soles. Adults not exclusively aquatic outside breeding period (Kuzmin & Thiesmeier, 2001).
Karyotype:
2n=66, 1M, 2M, 3T, 4T, 5T, 6M, 7T, 8T, 9T, 10M, 11ST, 12M, 13T, 14T, m (15–33), from Wang & Wu (1996).
M: metacentric; SM: submetacentric; T: telocentric; ST: subtelocentric; m: micro-chromosome
The mitochondrial genome has been sequenced by Zhang et al. (2003).
Large, robust salamander. Lungs present, but reduced. Vomerine teeth in two short, widely separated series. Prefrontal fontanel present. Paratoid glands well-developed. Labial fold often reduced or absent, but in some large animals well-developed. Big, protruding eyes. 11-13 costal grooves. Longitudinal groove running along the vertebral column from occipital region to tail base. Tail slightly longer than body length, or more or less of the same length. Tail cylindrical at base, tapering towards the tip. Four fingers, five toes. Males have a longer tail than females. During the breeding season, tail fin fold has fewer undulations and is higher in males than in females. Limbs and head are more muscular in males. Dorsal color yellow-brownish to dark olive and gray-greenish. Some individuals have a dark-spotted pattern on a dark-olive background. Color may change depending on environment. Aquatic adults may be darker than terrestrial individuals. Color becomes lighter with an increase of temperature. Under parts lighter than upper parts.
On the basis of 23 phenotypic characters, Zhao et al. (1988) considered Ranodon to be closely related to Onychodactylus. Zhao & Wu (1995) considered Pseudohynobius as a synonym of Ranodon. But mitochondrial genome data suggest that there is a sister relationship between Ranodon and Paradactylodon in central Asia, and that Pseudohynobius is distantly related to Ranodon (Zhang et al., 2006; Peng et al., 2010). Currently, Ranodon contains only one species.
This species is restricted to the southern and southwestern spurs of the Junggarian Alatau (Altao) Ridge in southern Kazakhstan and Mount Tianshan in Wenquan County, Xinjiang Uygur Autonomous Region, China. It may also occur in adjacent Yining, Huocheng and Tacheng Counties of China, and was historically also found in Hergos County. The range is severely fragmented and suitable habitats are scarce (Stuart et al., 2008; IUCN, 2010). The distribution is associated mainly with relic mountain coniferous forests or areas where forests have existed in the past, connected with the alpine, subalpine, forest-meadow and forest-meadow-steppe belts (Kuzmin et al., 1998).
This salamander inhabits slow-flowing streams on more or less flat plateaus with a dense network of permanent streams, at altitudes between 2,100 and 3,200 m, and summer water temperatures between 5 and 18 °C (IUCN, 2010). It prefers small, cold, spring-fed mountain streams with a variety of large boulders, stones and gravel on the bottom, where adults and larvae find sufficient shelter (Dolmen et al., 1997, 1999). Stream is 1–3 m wide and 10–30 cm deep (PH 5–6). The animal hides in shelters during the day and comes out after dark. Some may climb onto the bank into dense grasses (Fei et al., 2006). Larvae are also active during daytime (Dolmen et al., 1999). Hibernation takes place from end September, early October to end April or early June, depending on altitude (Kuzmin & Thiesmeier, 2001). The salamanders feed on both aquatic and terrestrial invertebrate prey, spending a considerable part of their life in water.
Reproduction occurs as soon as snow and ice melt and extends from end of April to early August. Ranodon sibericus tends to breed in small stream sources at the same site each year. It often attaches its egg sacs to the underside of great boulders, but may also attach them to large pebbles, plant stems and the bottom of streams (Dolmen et al., 1997; Greven et al., 1999). The species first breeds at the age of approximately five years and has a lifespan of 15-20 years (even longer in captivity) (Kuzmin & Thiesmeier, 2001; IUCN, 2010).
The behaviour shown before spawning was described from observations on captive animals in April 1985, kept in a tank with water temperature of 11°C (Thorn, 1994; Kuzmin & Thiesmeier, 2001). The male spent more time in the water than the female. Once both male and female were in the water, the male was alerted and sniffed the female’s flanks or tail base. Sometimes he gently bit her. When egg deposition was near, the female actively approached the male. She seized a part of the vegetation with her forelegs, pressed her cloaca against a rocky surface below the water surface and began to deposit the clutch. On seeing her spawn, the male approached the female, mounted her dorsally and clasped her body with his four limbs. He then proceeded to clasp the emerging egg sac with his forelegs, arched his back, pushed the female away from him and slid the egg sac against his cloaca. At this time fertilization probably took place. He wrapped his body round the egg sac by curling around it, his snout reaching his cloacal region (termed ball embrace). After about a minute, the male would fall to the bottom, go up for air and approach the female again, mount her, and the procedure would be repeated for the second egg sac. The entire procedure took approx. one hour. In the following hour the male was seen sticking his head between the egg sacs, moving them gently by moving his head laterally. In the following days the male tended to stay near the egg sacs and the female moved onto land. It is unclear whether this represents a form of clutch guarding (Thorn, 1994; Kuzmin & Thiesmeier, 2001).
The female produces two egg sacs, joined at the distal end by a mucous stalk, and attaches them to a stone. Just after deposition, the egg sac is tetrahedral in shape and has a bluish opalescence. Forty-eight hours after spawning the egg sac grows in size to approx. 48-60 mm. Egg sac parameters vary both between individuals and within a given clutch. The majority of clutches contains 38-58 eggs. In Xinjiang clutches of 32-50 eggs have been reported. In general, the number of eggs per clutch seems to depend on female size and, correspondingly, on egg sac size. The egg has almost no pigmentation. The egg is 3-5 mm in diameter. Larvae hatch at a size of 17-20 mm. Given the large amount of yolk in the eggs, larvae have a long endogenous nutrition period. Balancers are absent; long tail; short gills and cornified coverings on the tips of toes. Metamorphosis is usually after one or two hibernations at a length of 80-104 mm, depending on altitude and time of spawning (Kuzmin & Thiesmeier, 2001). The larva is of the rheophilous type, but in spite of adaptations to a life in streaming water, the robust body shape of the R. sibiricus larva resembles that of pond-dwelling larvae. Stages of normal development are illustrated in Kuzmin & Thiesmeier (2001).