Anderson's Salamander
(Ambystoma andersoni)
Anderson’s salamander exhibits some highly unusual and distinct features, indicative of its evolutionary distinctiveness, including its rare “neotenous” life history, whereby the species never develops into an adult but instead retains its juvenile characteristics throughout life, essentially achieving reproductive maturity whilst still in its undeveloped larval form. This would be akin to a tadpole being able to breed without ever turning into a frog. The species is totally aquatic, spending its whole life in the same body of water (Lake Zacapu). This lake is currently suffering from pollution which poses a major threat to the survival of the species.
Urgent Conservation Actions
Conservation and restoration of Anderson’s salamander habitat.
Central Mexico
The Anderson’s salamander species is a relatively recent discovery, first described in 1984. Its scientific name Ambystoma andersoni, and its English common name, was chosen in honour of James Anderson, a herpetologist at the American Museum of Natural History. James Anderson has carried out extensive fieldwork studying Ambystoma and other amphibian and reptile species in Mexico.

The family Ambystomatidae is also referred to as the mole salamanders because many live in burrows for much for their lives. They are found only in North America (from Canada down to Mexico), the majority (unlike Anderson’s salamander) metamorphose from aquatic larvae to become terrestrial adults that are rarely seen except in the breeding season, when they migrate to ponds to mate and deposit eggs.
Evolutionary Distinctiveness
Order: Caudata
Family: Ambystomatidae
The family Ambystomatidae or “the mole salamanders” is included within the four earliest or most primitive family lineages of the order “Caudata” (the salamanders), diverging from all other salamanders in the Early Cretaceous period over 140 million years ago, around five million years before the koala and dolphin lineages diverged from their common ancestor. The small number of species that represent the genus Ambystoma are highly evolutionarily distinct members of both the salamanders and the amphibians as a whole.

Anderson’s salamander exhibits some highly unusual and distinct features, indicative of its evolutionary distinctiveness, including its rare “neotenous” life history, whereby the species never develops into an adult but instead retains its juvenile characteristics throughout life, essentially achieving reproductive maturity whilst still in its undeveloped larval form. There are a couple of theories for why neoteny (also referred to as paedomorphosis) develops in some mole salamanders. One idea is that the production or effectiveness of the hormone thyroxine is compromised, either by the species living in water bodies containing insufficient iodine (which is required in the manufacture of thyroxine by the body) or in water temperatures that are too cold for the thyroxine to be effective. This impacts upon the development of the species and sexually mature adults never develop adult characteristics but remain in the larval form. A second theory suggests that species evolving in pools surrounded by hostile terrestrial environments develop aquatic lives to obviate the need to exit the relative safety of their watery home. This is a common trait in species that inhabit high-elevation ponds.
Anderson’s salamander is an Ambystomatid or mole salamander found only in Lake Zacapu near Zacapu, Mexico at an elevation of 2,000 meters above sea level. Mole salamanders are medium to large, stocky salamanders, usually measuring between 90 to 350mm from the tip of the nose to the end of the tail, which salamanders retain throughout their life. Males are often larger than females, owing to their longer tails. Ambystomatids generally exhibit both aquatic “neotenic” larval (or aquatic and permanently juvenile in form with external, feathery gills) and terrestrial “metamorphosed” (or ground-dwelling, fully developed adult in form with reduced gills) stages in their wild populations. Ambystomatids are often boldly patterned as adults, with well-developed “costal” grooves (successive vertical grooves along the sides of the body), especially the metamorphosing varieties. They have a rather flattened body with a wide, flattened head, a large mouth and smooth skin with many glands. The tail is roundish or laterally compressed, and, during the breeding season, males have a very swollen cloacal zone (the region around the reproductory and excretory opening in amphibians located underneath the base of the tail).

Like all neotenic Ambystoma species, Anderson’s salamander retains its larval features into adulthood. The mature salamander has medium-sized external gills with bright red filaments, and a prominent caudal (or tail) fin. It grows to a length of around 214 mm, with the tail accounting for about 40% of this measurement. A dorsal fin extends as a low ridge from the base of the gill rakers along the back to the base of the tail, where it rises about 13 mm to form the dorsal tail fin. This species has a large head and small, stocky limbs, as do the larvae. The toes are short and pointed with a slight degree of webbing. The skin colouration is a complex pattern of black blotches (some interconnected) on a red-brown base.
Anderson’s salamanders are totally aquatic and spend their whole lives in the same body of water. The species is paedomorphic (or permanently juvenile in physical characteristics), and reaches sexual maturity whilst still having the appearance of a larval salamander. This would be akin to a tadpole being able to breed without ever turning into a frog. It requires a clean, cool aquatic habitat and is found only in Lake Zacapu and the spring-fed streams and canals associated with the lake. Once the eggs are laid in water they are left to develop with no further participation by either parent. This species does not exhibit parental care.

Anderson’s salamanders do not metamorphosise from larval to adult form in nature, and individuals that have been artificially induced to metamorphosise with thyroid hormone in the laboratory do not thrive. The diet consists largely of snails and crawfish.
Its habitat is that of Lake Zacapu, a small lake near Zacapu, sitting at an altitude of 2000 meters above sea level. The lake is located within the Mesa Central portion of Mexico, an area home to many neotenic Ambystoma species. Lake Zacapu (or Lago de Zacapu) is temperate, with low salinity, and the Anderson’s salamander inhabits the main body of the lake and the spring-fed streams and canals associated with it, requiring a clean, cool aquatic habitat in order to survive.
Lake Zacapu (Lago Zacapu) and its surrounding streams near Zacapu, located in north-western Michoacan within the Mesa Central portion of Mexico at an altitude of 2000 metres above sea level.
Population Estimate
Population Trend
Anderson’s salamander is not currently rare in its small area of occupancy, but it is considered to be in decline by the IUCN Red List of Threatened Species.
Listed as Critically Endangered in the IUCN Red List of Threatened Species because its extent of occurrence is less than 100km sq. and its area of occupancy is less than 10km sq., all individuals are in a single subpopulation, and there is continuing decline in the extent and quality of the lake habitat around the city of Zacapu.

The major threat to the wild population is the pollution of Lake Zacapu, its sole habitat location. Additionally, the animals are heavily hunted for food by locals, and predatory fish have been introduced into the lake.  This may pose a severe problem if these fish prey extensively on the declining populations of Anderson’s salamander.

Conservation Underway
Anderson’s salamander does not occur in any protected area but the species could undergo a population recovery if Lake Zacapu can be kept clean and its ecosystem restored, including the control of introduced predatory fish and general levels of resource extraction from the lake and its associated streams and canals. Studies are needed to evaluate the sustainability of the harvest as well as on the impacts of introduced predatory fish. The species is protected under the category Pr (Special Protection) by the Government of Mexico.
Conservation Proposed
Conservation and restoration of Anderson’s salamander’s habitat is an urgent priority in order to save this species from extinction in the future. In addition to conserving wild habitat for this species, the IUCN Technical Guidelines for the Management of Ex situ Populations, part of the IUCN Red List of Threatened Species, recommend that all Critically Endangered species should have an ex situ population managed to guard against the extinction of the species. An ex situ population is ideally a breeding colony of a species maintained outside of its natural habitat, giving rise to individuals from that species that are sheltered from problems associated with their situation in the wild. This can be located within the species’ range or in a foreign country that has the facilities to support a captive breeding programme for that species. Anderson’s salamander can be bred in laboratory conditions and so captive animals could be a source of new individuals to repopulate the natural habitats within the species’ current range whilst its ecosystem is restored and an environmental management plan is developed for the species and its habitat.

However, any ex situ conservation measure is rendered ineffective if there remains insufficient natural habitat in which to release captive bred populations in the future. Clearly protected areas, sensitive land use techniques and the control of introduced predatory fish populations are of paramount importance to rescuing this critically endangered mole salamander from extinction in the wild.
AmphibiaWeb: Information on amphibian biology and conservation [web application]. 2006. Berkeley, California: AmphibiaWeb. Available: amphibiaweb. Accessed: 08 December 2006.

Dyer, W.G. 1988. Megalobatrachonema (Chabaudgolvania) elongata (Baird, 1858) Baker, 1986 (Nematoda: Kathlaniidae) in Ambystoma andersoni Krebs and Brandon, 1984 from Zacapu, Michoacan, Mexico. Transactions of the Illinois State Academy of Science. 81(3-4):275-277.

Frost, Darrel R. 2006. Amphibian Species of the World: an Online Reference. Version 4 (17 August 2006). Electronic Database accessible at: . American Museum of Natural History, New York, USA.

Frost, D. R., T. Grant, J. Faivovich, R. H. Bain, A. Haas, C. F. B. Haddad, R. O. De Sá, A. Channing, M. Wilkinson, S. C. Donnellan, C. J. Raxworthy, J. A. Campbell, B. L. Blotto, P. Moler, R. C. Drewes, R. A. Nussbaum, J. D. Lynch, D. M. Green, and W. C. Wheeler. 2006. The Amphibian Tree of Life. Bulletin of the American Museum of Natural History 297: 1-370.

Highton, R. 2000. Detecting cryptic species using allozyme data. The Biology of Plethodontid Salamanders. Bruce, R.C., Jaeger, R.G. and Houck, L.D.,editor. 215-241. Kluwer Academic / Plenum Publishers. New York.

IUCN, Conservation International and NatureServe. 2006. Global Amphibian Assessment. Global Amphibian Assessment. Accessed on 08 December 2006.

Krebs, S.L. and Brandon, R.A. 1984. A new species of salamander (Family Ambystomatidae) from Michoacan, Mexico. Herpetologica. 40(3):238-245.

Obst, F.J., Richter, K. and Jacob, U. 1984. The Completely Illustrated Atlas of Reptiles and Amphibians for the Terrarium. T.F.H. Publication Inc., N.J., U.S.A.

Roelants, K., Gower, D. J., Wilkinson, M., Loader, S. P., Biju, S. D., Guillaume, K., Moiau, L. and Bossuyt, F. 2007. Global patterns of diversification in the history of modern amphibians. Proceedings of the National Academy of Sciences 104: 887-892.

Shaffer, H.B. 1984. Evolution in a paedomorphic lineage. I. An electrophoretic analysis of the Mexican ambystomatid salamanders. Evolution. 38:1194-1206.

Shaffer, H.B. 1984. Evolution in a paedomorphic lineage. II. Allometry and form in the Mexican ambystomatid salamanders. Evolution. 38:1207-1218.

Shaffer, B., Flores-Villela, O., Parra Olea, G. and Wake, D. 2004. Ambystoma andersoni. In: IUCN 2006. 2006 IUCN Red List of Threatened Species. . Downloaded on 08 December 2006.

Shaffer, H.B. and Lauder, G.V. 1985. Patterns of variation in aquatic ambystomatid salamanders: kinematics of the feeding mechanism. Evolution. 39(1):83-92.

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