Lake Patzcuaro salamander
CITES Appendix II (CITES)[2]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Amphibia
Order: Urodela
Family: Ambystomatidae
Genus: Ambystoma
Species:
A. dumerilii
Binomial name
Ambystoma dumerilii
(Dugès, 1870)
Synonyms
  • Siredon dumerilii (Dugès, 1870)
  • Bathysiredon dumerilii (Emmett Reid Dunn , 1939)

The Lake Patzcuaro salamander, locally known as achoque (Ambystoma dumerilii) is a paedomorphic species of salamander found exclusively in Lake Pátzcuaro, a high-altitude lake in the Mexican state of Michoacán. First described in 1870 by Alfredo Dugès, the species is named in honor of the French herpetologist Auguste Duméril; however, the salamander has been used as a food source and an ingredient in traditional medicines by the Purépecha people since Pre-Columbian times. Ambystoma dumerilii are neotenic, meaning 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. When stressed, achoques can undergo an incomplete metamorphosis, though this is process significantly decreases their lifespan.

Due to pollution, overfishing, eutrophication, and invasive species, Ambystoma dumerilii are listed as critically endangered in the IUCN red list, and in Appendix II CITES. It is estimated that there are less than 100 individuals left in the wild, and the species may go extinct in the wild within the next 20 to 30 years. Currently, there are 4 in-situ colonies in Mexico and additional colonies maintained abroad. The most notable of these is run by Sisters of the Dominican Order, at the Basílica de Nuestra Señora de la Salud, who currently maintain a colony of 300 members, the largest known population of the species in the world.

Taxonomy and Evolution

Ambystoma dumerilii is a species of mole salamander located in the suborder Salamandroidea, also known as advanced salamanders. The species were first described in 1870 by Alfredo Dugès, who described the species as Siredon dumerilii.[3] The species epithet "dumerilii" is in honor of the French herpetologist Auguste Duméril.[4] In 1889, Edward Drinker Cope reclassified the species as Amblystoma dumerili, with the classification being upheld in 1930 by Karl Lafrentz. Emmett Reid Dunn renamed the species Bathysiredon dumerilii in 1939, and Hobart M Smith employed the name Siredon dumerilii that same year.[3] Between 1943 and 1948, Hobart M Smith, Walter Necker, and Edward Harrison Taylor returned the species to Bathysiredon dumerilii, but incorrectly claimed the species had gone extinct.[5] Manuel Maldonado Koerdell described the subspecies Bathysiredon dumerilii queretarensis and Bathysiredon dumerilii dumerilii.[6][3] A 2016 review of this classification concluded that the holotype specimen had been lost, making confirmation of Koerdell's discovery impossible. Previous assessments of the preserved specimen prior to them being lost concluded that the subspecies was not taxonomically valid.[5][7]

In 1958, Joseph Anton Tihen classified the species as Ambystoma (Bathysiredon) dumerilii. In 1976, Hobart M Smith, and Rozella B. Smith reclassified the species again as Ambystoma queretarense but this was rejected in 1992 by Southern Illinois University herpetologist Ronald A. Brandon.[3] In 1984, H. Bradley Shaffer conducted breeding experiments and genetic distance reviews of the Ambystoma genus, identifying Ambystoma dumerilii as part of the larger Ambystoma tigrinum species group.[5][8] In 2012, the species was lastly reclassified to its current name Ambystoma (Heterotriton) dumerilii by Alain Dubois and Jean Raffaëlli.[3]

The following cladogram shows the phylogenetic position of Ambystoma dumerilii among select members of the genus Ambystoma, based upon genetic distance comparisons of 32 loci via gel electroporesis:[8][lower-alpha 1]

Amblystoma  

Ambystoma mexicanum

Ambystoma amblycephalum

Ambystoma dumerilii

Ambystoma flavipiperatum

Ambystoma tigrinum

Ambystoma dumerilii are colloquially referred to as the Lake Patzcuaro Salamander, Dumeril’s salamander[9], and are locally called achoques.[3] The vernacular name achoque is derived from the Purépecha word 'achójki'. The term is synonymous with the Purépecha word 'axolotl', or the Spanish 'Ajolote'; which is broadly applied to all aquatic forms of branchiate salamanders.[5] The precise meaning of this word is not known, but it might mean 'mud'.[10]

Evolution

Ambystoma dumerilii evolved approximately 10 to 12 million years ago during the Neogene Era. The Ambystoma genus diverged following the uplifting of the Neovolcanic Axis where the Mexican plateau split from the Sierra Madre, isolating the ancestral species. From there, species along the Mexican Plateau split into 3 distinct lineages based upon the plateau's dranage patterns. Neotenic species of ambystomatids show significantly greater genetic divergence than metamorphosing species, indicating that neoteny restricts gene flow and hastens the process of speciation.[8]

Description

An adult specimen located at the Wilhelmshaven Aquarium.

Ambystoma dumerilii are large salamanders, adult specimen have a snout to vent length of 12.2 centimetres (4.8 in) and a size range of 12.8 centimetres (5.0 in) to 28.2 centimetres (11.1 in).[4] Males and females are identical lengths. Some adults have been observed growing over 35 centimetres (14 in) in length; this places achoques as one of the largest species in their genus.[9][10] The average adult weight is 121 grams (0.267 lb) and females typically weigh more than males. The salamander's skin has a granular to smooth texture, with small dome-shaped protuberances along the head. Their dorsum can range from tan brown to green, sometimes with dark brown spots, while their undersides are a pale grey. The toes, rostrum of the head, the cloaca, and underside of the tail tend to have a darker coloring compared to their body. Rarely, the dorsum can be darker in males, and the fimbriae of the gills are most often red colored.[9] Their dorsum color has been described by Chester Zoo curator Gerardo Garcia as " the color of Dijon mustard" and the salamanders "resemble miniature versions of the flying dragon-dog Falkor in The Neverending Story".[10]

Their head and mouth are flat and wide, and a caudal fin runs from the third gill arch to the end of the tail. This species also retains its gill rakers, and possess large, perennibranchiate (lifelong), hyperfilamentous gills that frame their head.[4][10] The eyes are small and located near the snout. Their bodies are widest along of thorax and begins to taper following the hind legs into the tail. The legs are short, stock, and their webbed toes end with 4 digits. Achoques are the only member of their species to retain webbed feet on all 4 limbs into adulthood.[9][4] Achoques are often compared to the axolotl, Anderson's salamander, and Taylor's salamander due to their shared geographical location, taxonomic ranking, and morphological features.[4][10] Compared to other Ambystoma species, their heads and rostrum are particularly flat. Additionally, their gills have a larger number of fimbriae but fewer gill rakers.[9]

Life Cycle

Mating occurs in winter and early spring.[4][6] Males intitial courtship by arching the base of their tails and swimming around the female; they lift their tails further to present their cloaca. If the female is receptive, she will begin to follow the male to a breeding site, where males release up to 16 spermatophores. Oviposition takes approximately 24 to 72 hours to complete, and individual eggs are attached to vegitation or rocks. Females can lay over 1000 eggs in a single clutch and eggs can measure up to 1.8 millimetres (0.071 in) in diameter.[9] Ova begin maturation during the spring's rainy season and spawning occurs in response to increasing seasonal temperatures.[4]

The life stages of achoques are largely defined by overall body length and the loss of some, but not all, larval features. Newly hatched salamanders measure approximately 12 millimetres (0.47 in) in length. They lack ectodermal projections (balancers), gill fimbriae, are a brown color, and have developing front limbs.[9] When larvae reach a 35 millimetres (1.4 in) snout to vent length, they have all limbs developed, hyperfilamentous gills, and have begun developing dark pigmentation. They largely retain their current features into maturity.[9] Stressors in the environment can induce morphological plasticity in larvae, which determines the length, width, and degree of tail development. When raised in captivity or under stressful conditions, achoques are generally smaller and have decreased swimming capabilities.[11]

Sexual maturity is achieved around 18 to 24 months of age, though some specimen can achieve this as early as 8 to 12 months. A snout to vent length of 108 millimetres (4.3 in) marks the beginning of sexual maturation while a snout to vent length of 122 millimetres (4.8 in) is considered sexually mature. Males tend to mature faster than females and can be identified by the swelling in their cloaca during breeding season. Females may be capable of reproducing earlier than this, but most of the resultant eggs would be unfertilized. The life span of this species is unknown but captive specimen can survive up to 16 years.[9]

Ambystoma dumerilii at the London Zoo, note the external gills and webbed feet.

Neoteny

This species is neotenic, meaning that they retain larval stage characteristics, namely their external, heavily vascularized gills, rather than losing them in adulthood.[4][10] While many of Ambystoma salamanders are capable of performing facilitative neoteny depending on environmental conditions, Ambystoma dumerilii is only one of four Ambystoma salamanders that are found in a permanent, natural state of paedomorphism.[9] As a result, while the species possesses functional, terrestrial lungs, most gas exchange occurs via their gills and skin.[9]

Metamorphosis

While the species is capable of undergoing metamorphosis, this does not occur naturally. Approximately, one third of both wild caught and laboratory raised specimen undergo metamorphosis in a laboratory setting but this has never been observed in the wild. Spontaneous metamorphoses often occur during mating season, indicating that this process is hormonally driven; the metamorphosis is largely incomplete and can take up to 3 years.[12][4] Incorrect husbandry practices are a source of stress in achoques in captivity and may be another driving factor in spontaneous metamorphosis.[11] Induction of metamorphosis via thyroxine shortens the lifespan of the salamander to 5 months from the start of metamorphosis, while non-induced lifespans only last 48 days on average.[12][4] These specimen will refuse to eat and require assisted feeding to survive.[9] Hybrids between A. dumerilii and its relatives, often A. mexicanum (the axolotl) and A. tigrinum (the Tiger Salamander), are also prone to spontaneous metamorphosis but show a stronger tolerance to survival.[4] This is because achoques lack the genes necessary to carry out metamorphosis to completion, often leading to detrimental phenotypes and bodily asymmetry.[11][12] Metamorphosed specimen do not undergo periodic molting, but rather continuously shed the stratum corneum. Unlike normal amphibians post transformation, the skin does not have Leydig nor mucosal cells.[4]

Behavior and ecology

Due to the species' rarity in the wild, most observations regarding their behavior have been made in captivity. Achoques are nocturnal, but will engage in opportunistic activities during the day. Movement is driven via a 'walking' motion through substrate and the tail fin is used for swimming when necessary. In their lungs, achoques regulate the amount of air to control buoyancy. When startled or attempting to swim, the salamanders pull their limbs to their body and dive down the water column. They will then hide in vegetation or substrate. Similar to axolotls, achoques are capable of limb regeneration following injury. Achoques do not normally vocalize but do make a croaking or squeaking sound when removed from water.[9]

Due to the lack of native, predatory fish, Ambystoma dumerilii was likely an apex predator in Pátzcuaro prior to the introduction of invasive species. They may have been predated on by herons and the snake Thamnophis eques patzcuarensis, but this has never been observed.[9] Ambystoma dumerilii is naturally paracitized by the fish lice curstacean Argulus ambystoma, which naturally is found on the salamander's skin and gills. It is unknown if this relationship poses any harm to achoques.[4][13]

Diet

Achoques feed by the use of gill rakers which they use to form a sucking motion to pull in food.[4] This is achieved via water being pushed though the buccal cavily and out the gills, trapping prey in the mouth. Juveniles and adults largely rely on smell to locate food and identify prey based upon movement. They can often be seen standing on their forelegs, and sweeping their snouts through substrate to find prey. Ambystoma dumerilii are generalist carnivores who commonly eat aquatic invertebrates, small fish, and eggs. They will often consume plant matter and algae, but this is most often incidentally consumed and provides little nutritional value. In the wild, Ambystoma dumerilii shows trophic specialization towards consuming the crustacean Cambarellus patzcuarensis, and wild-caught specimen will refuse other foods when offered. Larvae predominatly consume small invertibrates in large quanitites,[9] but have been observed engaging in cannibalism.[14]

In captivity, they are often fed beef liver.[4]

Interactions with Invasive Species

An invasive hyacinth species along Lake Pátzcuaro is a source of toxic metabolites detrimental to the salamander's health. Between the 1930s and 1970s, Oreochromis aureus, Cyprinus carpio (Carp), Micropterus salmoides (Largemouth bass), and Ctenopharyngodon idella were intentionally released into Lake Pátzcuaro; all of these fish predate on the eggs and larvae of achoques.[10][4][6] Achoques have shown an ability to coexist with these invasive species, a rarity amongst the Ambystoma genus. This indicates that the macronutrient competition between these species and achoques is limited. The introduction of these fish species also introduced a number of parasitic species from the Lerneae genus (namely Lernea cyprinacea) into the environment. These parasites colonize the gills of achoques, but their health impacts remain unknown.[9][6] Fungus species endemic to Europe also pose a risk to salamander's health.[10]

Distribution and threats

Ambystoma dumerilii is found exclusively in Lake Pátzcuaro, a high-altitude lake (1,920 metres (6,300 ft) in elevation[9]) in the Mexican state of Michoacán. Lake Pátzcuaro is an alkaline (pH 8.1 to 9.6) freshwater lake with a maximum historic depth of 11 metres (36 ft).[9] This is located in the Mesa Central Plateau, the exclusive home to many Ambystoma species. The last known wild population of achoques is located at the northern end of Lake Pátzcuaro.[10] 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.[4] The salamanders are most commonly found near the islands of La Pacanda and Tzitzipandácuri, and less commonly near La Ortiga and Santa Cruz Uricho.[6] The surrounding vegetation to Ambystoma dumerilii's habitat include oyamel forests, pine-oak forests, oak forests, and subtropical shrubs.[6]

While the exact location and number of achoques is unknown, the current extent of occurrence is estimated at under than 100 km2. Fishermen in 2021 reported that they were still finding juvenile specimen in their nets. This means that there exists a reproducing population, but the current health and survival rates of these larvae remains unknown.[9] In 2018, National Geographic estimated that there may be fewer than 100 individuals left in the wild and that the species could go completely extinct in the wild by 2040 to 2050.[15][16] This species is listed as Critically endangered in the IUCN red list, in Appendix II CITES, and is classified as a protected species (catagory PR) by the Mexico's Secretariat of Environment and Natural Resources. Despite this, no protective measures have been implemented by the Mexican government for the species or Lake Pátzcuaro.[9][16][15]

Habitat loss

Due to habitat destruction, and pollution resultant of the rising human population of Pátzcuaro, a city located on Lake Pátzcuaro, the achoque population has decreased severely in the past decades.[10] Lake Pátzcuaro is part of a larger basin, which makes the lake the final source for any runoff produced by the surrounding villages.[9] Silt, fertilizer, sewage, cow waste, and pollutant runoff, exacerbated by local deforestation, have negatively impacted water quality and resulted in eutrophication of the lake. Additionally, between 1982 and 2010, Lake Pátzcuaro lost a quarter of its total volume and water temperatures has significantly increased, further limiting the salamander's habitat. This is the result of siltation which has decreased the lake's depth by an estimated 2.6 metres (8.5 ft).[9][6][10] Efforts to rehabilitate the environment throughout the 1990s and 2000s were unsuccessful.[10]

Human interactions

Historically, fishermen have been harvesting achoques since Pre-Columbian times. The Purépecha people consumed achoques and often used them in traditional medicine. This medicine, often called 'Achoque soup', has been claimed to cure respiratory illnesses, cure anemia, give energy to children, and were often given to lactating women. Achoques were widely harvested throughout the 1970s and early 1980s until Lake Pátzcuaro's conditions deteriorated to the point at which their population crashed in 1989. Between 1987 and 2000, fishermen reported their harvests in kilograms per year, but official reporting of wild catches ceased being reported in 2000 due to population decline. In 2004, fishermen reported that due to over-fishing, they were only able to catch small specimen.[9][6][10]

Ambystoma dumerilii is subject to illegal pet trading.[10]

Conservation efforts

There exist four local in-situ breeding colonies, designed to prevent extinction. Two of these colonies are for species conservation, one is designated for educational purposes, and one is for commercial purposes. EAZA and the North American Association of Zoos and Aquariums also maintain populations abroad.[9]

Basílica de Nuestra Señora de la Salud

The most notable of the in-situ colonies is run by the Sisters of the Dominican Order, at the Basílica de Nuestra Señora de la Salud in Pátzcuaro. This colony is run in partnership with the Chester Zoo and Michoacan University.[10] The sisters have harvested achoques for use in traditional medicine for 150 years, using the achoque's skin in the production of jarabe, a cough syrup.[16] The origin of the recipe is unknown but possibly originates from the Purépecha. While there are other captive colonies throughout Pátzcuaro and Mexico, the monastery's colony is currently the largest known population of the species. Originally, the Sisters made syrup from specimen in Lake Pátzcuaro, but following the population's decline in the 1985, the Sisters established a colony to maintain their jarabe business and protect the species. By 2000, the colony was made self-sustaining through captive breeding efforts. As of 2018, the captive population is estimated to be approximately 300 specimen in two rooms, with a capacity to house 400 specimen at a time.[10][16] The achoques are measured, microchipped and paired for breeding by the sisters.[16]

Chester Zoo and Michoacan University also maintain colonies of achoques, but the population at the convent is considered the most viable since it is closest to the achoque's native habitat and the salamanders are thus less likely to be exposed to foreign pathogens.[16] Additionally, the current wild population has limited genetic diversity due to population bottle-necking, but the convent's population is believed by the Chester Zoo to have sufficient genetic diversity to reestablish a wild population. This reintroduction, however, is limited due to the relatively poor water quality of Lake Pátzcuaro.[10]

Michoacan University

Michoacan University's Laboratory of Aquatic Biology in Morelia City, Mexico maintains a colony at their campus. Research on the species focuses on captive management, achoque genetics, reproduction, and environmental education. As of 2021, the university's colony is made up of 10 breeding adults. Additionally, the university engages in outreach programs to increase awareness for achoque, including murals, radio broadcasts, and touring exhibitions. Michoacan University also partners with, and provides specimen to the two other in-situ colonies. The Centro Regional de Investigaciones Pesqueras Pátzcuaro and Gerardo León Murillo colonies focus on aquaculture research and educational programs, respectively, to reestablish populations of achoques for human consumption and medical use.[9]

See also

References

  1. ↑ IUCN SSC Amphibian Specialist Group (2020). "Ambystoma dumerilii". IUCN Red List of Threatened Species. 2020: e.T59055A53973725. doi:10.2305/IUCN.UK.2020-1.RLTS.T59055A53973725.en. Retrieved 13 November 2021.
  2. ↑ "Appendices | CITES". cites.org. Retrieved 2022-01-14.
  3. 1 2 3 4 5 6 "Ambystoma dumerilii (Dugès, 1870)". American Museum of Natural History.
  4. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 "AmphibiaWeb - Ambystoma dumerilii". amphibiaweb.org. Retrieved 2023-11-26.
  5. 1 2 3 4 Brandon, Ronald A (1965). "Ambystoma dumerilii". Catalogue of American Amphibians and Reptiles. 19 (2): 268–268. doi:10.1111/j.1558-5646.1965.tb01719.x. ISSN 0014-3820.
  6. 1 2 3 4 5 6 7 8 "Lake Patzcuaro Salamander". IUCN Red List. 2020.
  7. ↑ Flores-Villela, O., C. A. Ríos-Muñoz, G. E. Magaña-Cota, and N. L. Quezadas-Tapia. 2016. Alfredo Dugès’ type specimens of amphibians and reptiles revisited. Zootaxa 4092: 33–54.
  8. 1 2 3 Shaffer, H. Bradley (1984). "Evolution in a Paedomorphic Lineage. I. An Electrophoretic Analysis of the Mexican Ambystomatid Salamanders". Evolution. 38 (6): 1194–1206. doi:10.2307/2408628. ISSN 0014-3820.
  9. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Bland, Adam W.; Michaels, Christopher J.; Garcia, Gerardo; Tapley, Benjamin; Domínguez Domínguez, Omar; Rodríguez, Rodolfo Pérez; Vázquez, Luis H. Escalera; McLaren, Ellie; Lopez, Javier; Bamford, Paul (2021). "Best Practice Guidelines for The Lake Pátzcuaro salamander (Ambystoma dumerilii)" (PDF). EAZA Amphibian Taxon Advisory Group. Chester Zoo. 1.
  10. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Giller, Geoffrey (2018-07-30). "Vanishing in the Wild, These Salamanders Found Refuge in a Convent". The New York Times. ISSN 0362-4331. Retrieved 2023-11-25.
  11. 1 2 3 Suazo-Ortuño, Ireri; Ramírez-López, Berenice; Escalera, Luis; Domínguez-Domínguez, Omar (August 2023). "Morphological differentiation of Ambystoma dumerilii populations in captivity and wildlife conditions". Revista Mexicana de Biodiversidad. 94: 1–14. doi:10.22201/ib.20078706e.2023.94.4969.
  12. 1 2 3 Brandon, Ronald A. (1976). "Spontaneous and Induced Metamorphosis of Ambystoma dumerilii (Dugès), a Paedogenetic Mexican Salamander, under Laboratory Conditions". Herpetologica. 32 (4): 429–438. ISSN 0018-0831.
  13. ↑ Poly, William J. (2005-01-01). "Argulus yucatanus N. Sp. (Crustacea: Branchiura) Parasitic on Cichlasoma urophthalmus from Yucatan, Mexico". Gulf and Caribbean Research. 17. doi:10.18785/gcr.1701.01. ISSN 1528-0470.
  14. ↑ Estrada, Juan Jose; City, With Jennifer Gonzalez Covarrubias In Mexico. "Nuns get hands dirty, and wet, to save Mexico salamander". phys.org. Retrieved 2023-11-30.
  15. 1 2 "Conserving the Salamander: Our Journey to Mexico". Chester Zoo. Retrieved 2023-11-28.
  16. 1 2 3 4 5 6 Zachos, Elaina (19 June 2018). "Nuns Resurrect Endangered Salamanders in First-of-its-Kind Conservation Effort". National Geographic. Archived from the original on June 19, 2018. Retrieved 22 June 2018.

Notes

  1. ↑ Because many of these species are located within the Ambystoma tigrinum species group, only the relative position of Ambystoma tigrinum to Ambystoma dumerilii is shown to avoid redundancy. Ambystoma mexicanum and Ambystoma tigrinum are also closely related.

Further reading

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