Ambystoma andersoni is a pedomorphic species of Tiger Salamanders with adult male and females snout-vent length range from 100 to140 mm, 14 to 25 gill rakers on the anterior face of the third gill arch, and a short tail that is 56-78% of snout-vent length. The two sexes do not show sexual dimorphism in body proportions or in number of teeth. This species presents 14 costal grooves, 15 trunk vertebrae, 103 premaxillary/maxillary teeth, 35-38 vomerine teeth, and 19-16 palatine teeth. Toes are flattened and extensively webbed, extending nearly half the length of digits and two-thirds on hind feet. The posterior margin of hind foot conspicuously keeled and there are three rather than four phalanges in the fourth hind toe (Krebs and Brandon 1984).
Similar species include A. dumerilii, which also has short, highly webbed toes and 14 – 25 gill rackers, but A. andersoni is reddish-brown with spotting while A. dumerilii is uniformly brown with no markings. The two species also differ in A. dumerilii having hyperfilamentous gills, a smaller eye, smaller eggs, and larger body size at sexual maturity (Krebs and Brandon 1984).
In life, the body is reddish-brown marked with black dots that are sometimes interconnected, The dorsal coloring is reddish-brown even in preservative (Krebs and Brandon 1984).
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Mexico
Ambystoma andersoni has only been found at Laguna de Zacapu and the surrounding streams and canals that are above 2000 meters in elevation in Michoacan, Mexico. This lake is surrounded by soft mud and extensive vegetation (Krebs and Brandon 1984). This paedomorphic species lives in a cool, freshwater habitat (Shaffer et al. 2004). Many salamanders can be found hidden in vegetation at the deepest section of the stream where currents are strong. It is believed that their robust bodies, short tails, and reduced body fin are characteristic features adapted to live in the bottom vegetation with high currents (Krebs and Brandon 1984).
Life History, Abundance, Activity, and Special Behaviors
Ambystoma andersoni reach sexual maturity at one year of age (~87 mm snout-vent length), which can be observed by the swelling of the cloacal walls, and are believed to have comparable rate of growth, age, and size at maturity as Ambystoma mexicanum. This species follows a spring/summer breeding season. They produce dark yellow-brown colored eggs that are approximately 2.3 mm in diameter, and hatchlings are 12 - 13 mm in length and lack balancers (Krebs and Brandon 1984). This species does not metamorphose in nature, and those that are artificially induced do not thrive (Shaffer et al. 2004).
Though this species is not believed to be rare, Ambystoma andersoni has only been found in one location and pollution of its habitat and predatory fish have contributed to a decreasing population trend. Ambystoma andersoni are known to eat snail and crawfish (Shaffer et al. 2004).
Trends and Threats
The major threat that has caused a decline in this species population is pollution of its habitat (IUCN 2004). Though Lake Zacapu is not a protected area, Ambystoma andersoni is classified as a protected species by the Mexican government (Shaffer et al. 2004).
Relation to Humans
This species is heavily harvested for food, which is a major contribution to its decreasing population (Shaffer et al. 2004).
Possible reasons for amphibian decline
General habitat alteration and loss
Predators (natural or introduced)
Intentional mortality (over-harvesting, pet trade or collecting)
The species authorities are Krebs and Brandon (1984).
Krebs, S.L. and Brandon, R.A. 1984. A new species of salamander (Family Ambystomatidae) from Michoacan, Mexico. Herpetologica: 238-245
Shaffer, H.B, Flores-Villela, O., Parra-Olea, G., Wake, D. 2004. Ambystoma andersoni. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. Downloaded on 03 May 2013.
Written by Christina Kang (c.kang AT berkeley.edu), University of California, Berkeley
First submitted 2013-06-12
Edited by Ann T. Chang (2013-07-14)
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