Lake Patzcuaro Salamander

Ambystoma dumerilii is a neotenic salamander found only in Lake Pátzcuaro, Mexico. A sexually mature specimen measures, from snout to vent, over 122 mm; there is no body length difference between the sexes. Of preserved specimens, total size ranges from 128-282 mm (Brandon 1970). Distinct features include a flat, wide head, caudal fins, and few rakers on the third gill arch’s anterior surface (the exact number is disputed). The salamander can also be identified by perennibranchiate (lifelong), hyperfilamentous gills and diminutive, webbed toes with the fourth digit possessing three phalanges (Brandon 1992, Smith 1948). This animal is tan to brown and homogenous in coloration (Brandon 1992, Smith 1948).The species authority is: Dugès, A. A. D. 1870. Una nueva especie de ajolote de la Laguna de Patzcuaro. La Naturaleza. México 1: 241–244.The species was previously placed in Bathysiredon or Siredon (Brandon 1992, Smith 1948). Nuns from the convent at the Basílica de Nuestra Señora de la Salud in Pátzcuaro, Mexico have a captive breeding population (https://www.nytimes.com/2018/07/30/science/achoques-salamanders-nuns-mexico.html) of about 300 individual A. dumerilii from which they make a cough syrup. The population is considered vital to the conservation of the species (Giller 2018). ReferencesBrandon, R.A. 1970. Size range maturity, and reproduction of Ambystoma (bathysiredon) dumerilii (Dugès), a paedogenetic Mexican salamander endemic to Lake Pátzcuaro, Michoacán. Copeia 1970: 385-388. Brandon, R.A. 1976. Spontaneous and induced metamorphosis of Ambystoma dumerilii (Dugès), a paedogenetic Mexican salamander, under laboratory conditions. Herpetologica 32: 429-438.Brandon, R.A. 1977. Interspecific hybridization among Mexican and United States salamanders of the genus Ambystoma under laboratory conditions Herpetologica 33: 133-152Brandon, R.A. 1992. Ambystoma dumerilii. Catalogue of American Amphibians and Reptiles 532: 1-3.Poly, W.J. 2003. Argulus ambystoma, a new species parasitic on the salamander Ambystoma duerilii from Mexico (Crustacea: Branchiura: Argulidae). Ohio Journal of Science 103: 52-61Smith, H.M. Taylor, E. 1948. An Annotated Checklist and Key to the Amphibia of Mexico. Smithsonian Institution Bulletin 194: 1-118

The amphibian is known historically and currently to inhabit only Lake Pátzcuaro in the Mexican state of Michoacan (Brandon, 1970). Rumors of salamander sightings in San Juan del Rio, Queretaro, are highly unlikely due to geographic isolation. Area of occurrence is less than 100 km2, the occupancy area less than 10 km2 (Shaffer et al. 2008).

Metamorphosis in nature has not been observed although roughly a third of both wild-caught and first generation laboratory animals undergo the process according to research conducted at Carbondale, Illinois (Brandon, 1976). Hybrids between A. dumerilii and relatives, such as A. mexicanum and A. tigrinum are also prone to metamorphose (Brandon, 1977). Spontaneous transformations generally occur during breeding seasons, suggesting a hormonal association. Adult animals do not experience periodic ecdysis (molting), but continuously shed the stratum corneum (exterior skin). The transformed skin does not include Leydig and mucous cells like normal adult amphibian skin. An incomplete metamorphosis over a period up to three years indicates that the change is unnatural for the species; no spontaneously transformed animal lived over five months and no induced transformed animal lived over 48 days from the beginning of morph (Brandon 1976). Ova mature during the rainy seasons and spawning occurs with increasing atmospheric temperatures; breeding observed during winter (IUCN 2004) and spring (Brandon 1970). Salamanders feed by suction and sport distinguishably few “tooth-like rakers” as described above (IUCN 2004) - laboratory animals thrive on beef liver (Brandon 1970). Argulus ambystoma, a new species of parasitic crustaceans (fish lice) found on fish, a crayfish, and A. dumerilii of Lake Patzcuaro, resides on the skin surface and retreats to the gills of hosts upon exposure to light; its threat to A. dumerilii is unknown (Poly 2003).

Amybstoma dumerilii is listed on the IUCN Red List as "Critically Endangered" because it is only known from Lake Pátzcuaro, Mexico and is experiencing habitat degradation from lake infill and pollution. The decline in this species is based largely on the historical vs. present numbers reported by local fishermen, who harvested the species for human consumption (Shaffer et al. 2008). In the 1930's, it was feared that the introduction of largemouth bass would decimate amphibian colonies, however, no salamander decline was recorded to have been directly attributed to the foreign fish (Brandon 1970) and the species seems to be one of the few salamander species that are able to co-habitat with largemouth bass. Unfortunately, given the small population size, largemouth bass may still be a threat to the species (Shaffer et al. 2008).Ambystoma dumerilii is locally protected by the Mexican government and has global trade restrictions (Shaffer et al. 2008). There are efforts to captively breed the species for both conservation and commercial uses (Giller 2018, Shaffer et al. 2008).

Known locally as Achoque, the species is harvested by the indigenous Tarascan people for consumption and for its believed medicinal properties as a respiratory remedy (Shaffer et al. 2008). In 2018, it was reported in the New York Times that a convent of Dominican nuns (https://www.nytimes.com/2018/07/30/science/achoques-salamanders-nuns-mexico.html) living at the Basílica de Nuestra Señora de la Salud in Pátzcuaro, Mexico had a healthy colony of about 300 individual A. dumerilii, which they use to make cough syrup. The convent colony is the largest captive population of the species (Giller 2018). Experts believe that captive breeding can work as a source for reintroductions in the future (Giller 2018, Shaffer et al. 2008).

The Lake Patzcuaro salamander, locally known as achoque (Ambystoma dumerilii) is a neotenic salamander species.

This salamander is found in Lake Pátzcuaro, a high-altitude lake in the Mexican state of Michoacán. This is located in the Mesa Central region of the country, home to many isolated Ambystoma species.

There have been claims that a subspecies is found further inland to the north-east in San Juan del Río, Querétaro, but this is doubtful due to the animal's wholly aquatic nature.

Dumerilii are paedomorphic, similar to Ambystoma mexicanum, where they retain their larval characteristics throughout their entire life. This results in adults that have long, heavily filamented external gills, gill slits lined with tooth-like gill rakers, and caudal fins.

Patzcuaro salamanders are usually yellowish in color, with a lighter shade on their underbellies. They have large heads and reduced limbs. They are opportunistic suction feeders, and eat many types of invertebrates.

Recently, this salamander has been used in research as a counterpoint to the more common captive-bred axolotl. Patzcuaro salamanders have been hybridized with axolotls, and used in mitochondrial studies for comparison.

Due to habitat destruction, pollution and the introduction of predatory fish the population has decreased severely in the past decades. It is listed as Critically endangered in the IUCN red list and in Appendix II CITES. There may be fewer than 100 individuals in the wild.