Description
Ambystoma amblycephalum is a medium sized, facultative-paedomorphic salamander with females ranging from 42 - 93 mm in standard length and males ranging from 45.4 - 70.5. Females, with total lengths up to 161 mm, grow larger than males with total lengths up to 128.8 mm (Hernandez et al. 2022). In metamorphic adults, the head is shallow and longer than broad with pits present near their small eyes. There is a distinct fold along the angle of the jaw. The species has 11 costal grooves. When adpressed, their long and sturdy limbs usually overlap the same distance as the size of their hands. The bottom of their feet have tubercles and are webbed up to the base of their fingers/toes. The tail, which is as long as the body, has a slight ridge present, but lacks a total caudal fin (Taylor 1940).

DIAGNOSIS: (How this species is different from similar species)

Ambystoma amblycephalum has 11 costal grooves compared to 13 in A. flavipiperatum (Hernandez et al. 2022). They are larger than A. velasci and A. bombypellum and have different body proportions, such as how A. amblycephalum has a less compressed body than A. lermaense. The tail in A. amblycephalum is smaller compared to A. flavipiperatum. A greater number of premaxillary teeth are present in this species than others (around 70). Ambystoma amblycephalum possesses darker and more olive colored spots than A. velasci and possesses light ventral spots, which A. lermaense lacks. Ambystoma ordinarium lacks the webbing present on the base of the toes that A. amblycephalum possesses (Taylor 1940).

COLORATION:

Metamorphosed individuals are blackish dorsally with cream or olive spots on the lower sides and tail, while the venter is lighter with cream colored markings (Taylor and Smith 1945).

Paedomorphic adults are lighter than larvae, often with a greenish-yellow background with dark markings, although some have been found to have a grayish background with large cream blotches (Fraustros-Sandoval et al. 2024).

VARIATION:

Besides size, there is some sexual dimorphism as females don’t have very pronounced markings (Taylor 1940). Additionally, a paedomorphic specimen observed by Fraustros-Sandoval et al. (2024) changed color over the course of almost a year. Color changes like this are associated with adaptation to temperature and other environmental factors. The abnormal coloration seen in these specimens could have been due to the pollution of the pond they inhabited.

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Mexico

View distribution map in BerkeleyMapper.

Ambystoma amblycephalum are native to northwest Michoacán near Morelia, Mexico (Taylor 1940). There are also populations near Tapalpa Jalisco (Fraustros-Sandoval et al. 2024). They range within, often altered and fragmented, hilly pine forest in the vicinity of agricultural land around 2,500 m in elevation. Many species of shrubs and grasses are present in the area and their habitat is present on basaltic lava flows. The area consists of year round humid temperate conditions with a warm rainy season in the summer. They have been found to take refuge under logs, often near breeding sites (Hernandez et al. 2022).

Life History, Abundance, Activity, and Special Behaviors
The species breeds in small stagnant water sources like cattle ponds, often with muddy bottoms and the presence of aquatic vegetation (Hernandez et al. 2022). The adults will remain hidden in burrows most of the year like other ambystomatids, likely in times other than breeding season (Hernandez et al. 2022).

Potential clutches of this species were comprised of 170 - 220 eggs in single masses laid on roots/other vegetation (Hernandez et al. 2022).

Larva
Most larvae range in standard length by 60 - 77 mm. They possess a long, blunt, flat head with a thin labial fold and large gills. They have indistinct costal grooves and the presence of a large dorsal fin (Taylor and Smith 1945).

Coloration consists of red gills, and a black background with small light spots on the side (Taylor and Smith 1945).

Larvae of A. amblycephalum resemble A. velasci, but have different coloration (Taylor and Smith 1945).

The larvae most likely consume aquatic insects and their larvae such as Daphnia and Chironomus, which have been observed nearby (Hernandez et al. 2022).

Trends and Threats
They are threatened by habitat alteration due to the cattle rearing industry as well as logging, pollution, and introduced fish. They are also poached by locals (Hernandez et al. 2022).

A new population was discovered in a cattle pond near Nahuatzen in 2018 (Hernandez et al. 2022).

Relation to Humans
The species is poached and presumably eaten (Hernandez et al. 2022)

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing
Local pesticides, fertilizers, and pollutants
Predators (natural or introduced)
Introduced competitors

Comments
According to Bayesian and maximum likelihood analysis in Everson et al. 2021, A. amblycephalum is sister to A. flavipiperatum, which are both sisters to the clade composed of A. dumerilii and A. andersoni. Everson et al. (2021) also recommended that A. amblycephalum and A. flavipiperatum should be synonymized. Using mitochondrial barcoding the A. amblycephalum population from Nahuatzen wasn’t completely identical to A. amblycephalum and showed potential relations to A. velasci, A. flavipiperatum and A. mexicanum (Hernandez et al. 2022).

Ambystoma amblycephalum has only been genetically confirmed two times since first being described in 1940 (Hernandez et al. 2022).

OTHER INTERESTING INFORMATION:

References
Everson, K. M., Gray, L. N., Jones, A. G., Lawrence, N. M., Foley, M. E., Sovacool, K. L., Kratovil, J. D., Hotaling, S., Hime, P. M., Storfer, A., Parra-Olea, G., Percino-Daniel, R., Aguilar-Miguel, X., O’Neill, E. M., Zambrano, L., Shaffer, H. B., and Weisrock, D. W. (2021). Geography is more important than life history in the recent diversification of the Tiger Salamander Complex. Proceedings of the National Academy of Sciences, 118(17), e2014719118. [link]

Fraustros-Sandoval, A. J., Dávalos-Martínez, A., Rosas-Espinoza, V. C., Cortés-Arévalo, S. A., Navarrete Heredia, J. L., and Santiago-Pérez, A. L. (2024). A temporal color variant in the Blunt-headed Salamander (Ambystoma amblycephalum) in west-central Mexico. Western North American Naturalist 84(1), 158–162. [link]

Hernandez, A., Dufresnes, C., Raffaëlli, J., Jelsch, E., Dubey, S., Santiago-Pérez, A. L., Rosas-Espinoza, V. C., and Nuñez, P. B. (2022). Hope in the dark: Discovery of a population related to the presumably extinct micro-endemic blunt-headed salamander (ambystoma amblycephalum). Neotropical Biodiversity, 8(1), 35–44. [link]

Taylor, E. H. (1940). New salamanders from Mexico, with a discussion of certain known forms. University of Kansas Science Bulletin 26, 407–430. [link]

Taylor, E. H., and Smith, H. M. (1945). Summary of the collections of amphibians made in Mexico under the Walter Rathbone Bacon traveling scholarship. Proceedings of the United States National Museum, 95(3185), 521–613. [link]

Species Account Citation: AmphibiaWeb 2024 Ambystoma amblycephalum: Blunt-headed Salamander <https://amphibiaweb.org/species/3823> University of California, Berkeley, CA, USA. Accessed Nov 12, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 12 Nov 2024.

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