Axolotl (Ambystoma mexicanum) Fact Sheet: Reproduction & Development

Courtship behavior

• Female and male follow each other in a circle (Gasco 1881); courtship display described as a ‘hula dance’ (Gresens 2004; Park et al. 2004) or ‘waltz’ (Salthe 1967; Malacinski 1978)
  • Female and male pursue each other, nudging, caressing, and biting
  • Male opens cloaca (external slit opening for reproduction and digestive waste), and undulates body and tail
    • Secretes courtship pheromones (Sever 1992; Maex et al. 2016)
      • Also see Olfactory communication
  • Female nudges male’s cloaca
  • Male then deposits cone-shaped sperm packets (up to 12) on lake bottom
  • Female follows male and collects sperm using her cloaca
  • Female lays eggs a few days later

Breeding

• Sexual maturity
• Around 1.5 years old (IUCN SSC Amphibian Specialist Group 2020)
• Possibly shorter in managed care (Malacinski 1978; Pasmans et al. 2014)
• Breeding interval

• In managed care, females can breed several times per year (Eisthen and Krause 2012)

• Lowest breeding activity during summer months

• Annual cycle for wild axolotls not known (Eisthen and Krause 2012)

• Seasonal factors, such as photoperiod and water temperature, may influence frequency of reproduction
• Hybridization
• Members of the genus Ambystoma easily hybridize with one another (Brandon 1989)

Fertilization

• Fertilization occurs internally but no copulation (similar to other mole salamanders, Family Ambystomatidae) (e.g., Gasco 1881; Maex et al. 2016)
• Eggs fertilized by stored sperm, then coated in clear mucus and laid on plants or rocks (Gresens 2004)

Egg laying

• Females can lay between 200 and 1,500 eggs every 3–6 months [managed care] (Gasco 1881; Voss et al. 2009; Gresens 2004; Griffiths, Bride, et al. 2004; Sciences et al. 2006; Mansour et al. 2011; Pasmans et al. 2014)
• Eggs laid in clumps in underwater vegetation

Early development

• Incubation period
• Eggs hatch after about 2 weeks at 20°C (70°F) (Gresens 2004) but may take up to 3–4 weeks (Serrano 2011)
• Egg development in managed care influenced by water temperature and possibly other water conditions (Serrano 2011)
• Hatchling size
• Embryos 2–3 mm in diameter (Gresens 2004)
• Early nutrition
• Larvae have internal yolk sac (Gresens 2004)
• Provides nourishment for about a week after hatching
• Early growth
• Includes limb and gill elongation/branching (Schreckenberg and Jacobson 1975)
• For developmental progression from egg to larva, see Schreckenberg and Jacobson (1975)

Wild populations

• Not reported

Managed care

• No AZA estimates
• Other studies suggest about 10 years (Malacinski 1978; Griffiths, Bride, et al. 2004; IUCN SSC Amphibian Specialist Group 2020)

Survival rates

• High mortality rates of eggs and larvae (first year of life) (Zambrano 2006)
• Hatchling survival suggested to be 30–40% (Legorreta 2002, as cited by Serrano 2011; Serrano 2011)
• Population stability most dependent on survival of eggs and larvae (Zambrano et al. 2007)

Predators

• Introduced fish: carp and tilapia (Tapia and Zambrano 2003; Zambrano 2006; Zambrano et al. 2007)
• “Feed on axolotl larvae and juveniles and harass adults” (Ayala et al. 2019)
• Native crayfish (Cambarellus montezumae) feed on larvae (Zambrano et al. 2015)
• Aquatic birds (Zambrano et al. 2007)
• Snakes (Zambrano et al. 2007)

Diseases (non-comprehensive list)

• Recuero et al. (2010) observed a pathogenic fungus (Saprolegnia spp.) in two adult axolotl in Chapultepec Lake
• Immunity may have been weakened by pollution or other diseases
• Frías-Alvarez et al. (2008) found a large number of individuals with chytrid fungus, Batrachochytrium dendrobatidis, in one Mexico City university colony
• Most common diseases/conditions in pet animals (Takami and Une 2017):
• Buoyancy disorders
• Hydrocoelom
• A bulbous distension in the body, sometimes caused by accumulating fluid
• Skin diseases

Parasites (non-comprehensive list)

• High prevalence of parasites observed in Chapultepec Lake population (Recuero et al. 2010)
• Nematode Eustrongylides
• Not thought to contribute to amphibian declines; final host is fish-eating birds
• Associated with aquatic habitats altered by humans (polluted bodies of water)
• Copepods (e.g., Lernaea)

Female axolotls protect their eggs by laying them in underwater vegetation.

Though not well studied in the wild, it's thought females can lay hundreds or even more than 1,000 eggs several times a year, under good conditions.

Large clutch sizes may aid the recovery of axolotl populations, if Xochimilco's water quality can be improved and invasive predators removed. Axolotls are critically endangered in the wild.

Image credit: © San Diego Zoo Wildlife Alliance. All rights reserved.

Axolotl embryo and hatchling.

Image credits: © John P. Clare via Flickr (embryo, hatchling). Some rights reserved.