Chinese Giant Salamanders (Andrias spp.) Fact Sheet: Reproduction & Development

Mating system (wild populations)

• Not well known (Ben Tapley, personal communication, 2019)
  • Possibly polygynous (1 male, multiple females) (Liang and Wu 2010; Browne et al. 2014)
    • Eggs at a nest site laid by several females
    • Dominant male fertilizes and defends eggs

Courtship behavior and interlocking

• Male waits at entrance to breeding den (see “Den preparation,” below) (Nickerson 2004)
  • Allows female to enter den or chases her into den
• Courtship behaviors (Liang and Wu 2010; Luo, Tong, et al. 2018)
  • Male–female stand side by side with heads touching
  • Male pushes belly of female
  • Male climbs on female’s back or rests head on female’s back
  • Pair postures mouth to mouth
• As female lays eggs into slight depression, male moves alongside her and releases sperm over egg mass (Laidler and Laidler 1996; Nickerson 2004)

Breeding

• Sexual maturity
  • Best available estimate is 5 to 6 years old, but possibly up to 8 years old—possibly longer (Cheng 1998; Xiao et al. 2006; Zhang et al. 2017)
    • Not known for most populations (Benjamin Tapley, personal communication, 2019)
• Breed annually in the wild populations (Xiao et al. 2006)
  • Seasonal progression (Browne et al. 2014, and as noted):
    • Spring to summer: maturation of gonads (May to late July)
      • Initiated by warming water temperatures (Xiao et al. 2006)
    • Summer: spawning (August to mid-September)
      • Corresponds with warmest annual water temperatures (Zhang et al. 2006, as cited by Browne et al. 2014)
    • Early winter: brooding of young and larval development
    • Winter: adults inactive; larvae leave den and shelter in river gravel/debris
• Some salamander farmers induce reproduction (sperm development, ovulation of eggs) using hormone injections (Xiao et al. 2006)
  • Natural breeding is becoming increasingly common (Benjamin Tapley, personal communication, 2019)

Den preparation

• Dens are hollows located under rocks or in riverbank (Luo, Tong, et al. 2018)
  • Site where female lays eggs, and male fertilizes eggs and broods young
• Male prepares den, clearing out sand or gravel from den space to increase den’s size and water depth (Liang and Wu 2010; Luo, Tong, et al. 2018)
  • Uses limbs, tail, and sometimes head
• Entrance often faces downstream (Nickerson 2004)

Egg laying

• Female lays a string of eggs within male’s den (Liang et al. 2004; Luo, Tong, et al. 2018, and as noted)
  • Lays 10 to 100 eggs several times during breeding season
    • Up to approximately 500 eggs per breeding season (Xiao et al. 2006)
  • Eggs then fertilized externally by the male
  • Egg laying and fertilization may be repeated up to 7 times, lasting up to 3 hours
• Egg description (Cheng 1998)
  • Color
    • Golden yellow or whitish
  • Size
    • Initially, 7 to 8 mm (0.3 in) in diameter
    • After absorbing water, 15 to 20 mm (0.59 to 0.79 in) in diameter

Hatching

• Larvae description
  • Photo: Dai et al. (2010), Fig. 12
  • Tadpole-like (Nickerson 2004)
    • Gills external
    • Tail well developed
    • At about 2 weeks old, short limbs present
    • See additional description in Liu and Tang (1989)
  • Size (length)
    • At hatching: 2 to 3 cm (0.8 to 1 in) (Tapley et al. 2017)
    • 6 to 8 days after hatching: 3.5 to 4.0 cm (1.4 to 1.6 in) (Liu and Tang 1989)
      • 26 days after hatching: 3.9 to 4.5 cm (1.5 to 1.8 in) (Liu and Tang 1989)
  • Weight
    • Not well reported
    • Liu and Tang (1989) state about 0.30 g at hatching
  • Coloration (Liu and Tang 1989; Dai et al. 2010)
    • First month of age
      • Upperbody bright brown-red
      • Underbody (yolk sac) golden yellow
      • Small black spots cover entire body
    • Older than 1 month
      • Upperbody brown with larger black spots
      • Underbody yellowish white
    • Older than 5 months
      • Upperbody brownish black
      • Underbody dark purplish red
• In the wild
  • Larvae grow and develop in a stream (Liang et al. 2004)
  • Leave nest at 4 to 5 cm (about 2 in) long (Tapley et al. 2017)
  • Emerge from springs, in populations where adults live in caves (Dai et al. 2010; Browne et al. 2014)
• Managed care
  • Incubation period
    • Eggs hatch after about 45 (range: 35-50) days (Liu and Tang 1989; Haker 1997)
  • Larvae begin to feed about 30 days later (Haker 1997)
• Influences on egg development and hatching success:
  • Fertilization rate (C. Yang et al. 2018)
  • Water temperature (Cheng 1998)
  • Water flow (C. Yang et al. 2018)
    • Bacteria may infect eggs if water movement insufficient (especially on farms, where feces contaminate holding areas)

Parental care behaviors

• Male agitates eggs by fanning tail within or next to egg cluster (Luo, Tong, et al. 2018)
• Male eats unfertilized or decomposing eggs (Luo, Tong, et al. 2018)
• Male may guard eggs and larvae for up to 4 months, until young feed independently (Liang and Wu 2010; Browne et al. 2014)
• Cheng (1998) suggests larvae may be protected by parents for 10 to 15 days
• Male does not eat until young grow larger (Browne et al. 2014)

Nourishment of young

• During first month of life, larvae absorb nutrients from yolk sac (Liu and Tang 1989)
  • Gradually begin to eat food
    • Diet not well known (Ben Tapley, personal communication, 2019)
      • In aquaculture, may eat larvae of mosquitos and flies, small aquatic insects, shrimp, etc. (Liu and Tang 1989)
  • Feed mainly at night, similar to adults (Liu and Tang 1989)

Hatchling

• Larvae remain in nest/den for up to 4 months (Browne et al. 2014)
  • Guarded by male
• Large larvae shelter in more exposed sites, outside of den: under small rocks and in river debris (Browne et al. 2014)
  • Still avoid light (Liu and Tang 1989)
  • Possibly shelter within parents’ den at night (Cheng 1998)
• At about 6 months, larvae begin to shed skin (once a month or more) (Liu and Tang 1989)
  • Larvae may consume the shed skin
• See “Hatching” in Incubation and Hatching
• Characteristics of growth and development: see Liu and Tang (1989), Table 3

Juvenile

• Weight at 1 year old: 10 to 30 g (0.3 to 1 oz) (managed care) (Liu and Tang 1989)
• Transition from free-swimming larva to bottom-dwelling adult (Laidler and Laidler 1996)
  • Rate of development influenced by water temperature and food availability
• Metamorphosis
  • Gills degenerate at 2 to 3 years of age, as lungs develop (Cheng 1998; Heiss et al. 2013; Su et al. 2018)
  • Head and mouth structures change (Heiss et al. 2013)
  • Digestive tract develops distinct structures (Zhang et al. 2018)
• Diet
  • Appears to shift to shrimp and crabs at about 3 to 4 years old (Zhang et al. 2018)

Maximum lifespan not yet established

• Thought to live 50 to 60 years or longer, based on longevity of similar species (Nickerson 2004; Browne et al. 2014; AnAge 2019)
• At least 25 years in managed care (ZIMS 2019)
  • Not well documented

Survival rates

• Cheng (1998) reports a hatching success rate of 30% (wild population)
• Liu and Tang (1989) report a 1-year survival rate as high as 91% (managed care)

Predators

• Juveniles and adults
  • Potentially, mountain carnivores
    • Eurasian otter, Lutra lutra (Zhang et al. 2017)
    • Red fox, Vulpes vulpes (Zheng and Wang 2010)
    • Siberian weasel, Mustela sibirica (Zheng and Wang 2010)
    • Hog badger, Arctonya collaris (Zheng and Wang 2010)

Diseases (non-comprehensive list)

• Infectious diseases and bacterial infections prevalent in Chinese giant salamander aquaculture (e.g., Zhou et al. 2013; Meng et al. 2014; Cunningham et al. 2016; Z.-Y. Chen et al. 2018)
• Ranaviruses are the main diseases of concern (Geng et al. 2011; Chen et al. 2013; Zhou et al. 2013; Geng et al. 2016; Z.-Y. Chen et al. 2018; Meng et al. 2018, and as noted)
  • First reported by Geng et al. (2011)
  • Infections often fatal; cause substantial losses on farms
    • High mortality (60 to 95%) during outbreaks on farms
      • Juvenile mortality higher than adult mortality
      • Larval mortality also high (Meng et al. 2014)
    • Sick individuals typically die 1 to 2 weeks after infection
      • Up to 5 weeks, according to Geng et al. (2016)
  • Symptoms (Meng et al. 2014)
    • Juveniles and adults (Cunningham et al. 2016)
      • Swelling, bleeding, ulcers, and necrosis/hemorrhaging of various tissues and organs
      • Also lethargy, vomiting, bloody stools, and weight loss
    • Larvae (Meng et al. 2014)
      • Lethargy
      • Swelling
      • Hemorrhaging
  • No widespread treatment yet available (Z.-Y. Chen et al. 2018)
    • Some success in some early vaccines (e.g., Z.-Y. Chen et al. 2018)
• Ranaviruses reported for some wild populations (Dong et al. 2011)
  • Not well studied