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Axolotl

Ambystoma mexicanum

Summary 6

The axolotl (/ˈæksəlɒtəl/; etymol. Nāhuatl āxōlōtl (singular) or āxōlōmeh (plural) "water monster"), also known as a Mexican salamander (Ambystoma mexicanum) or a Mexican walking fish, is a neotenic salamander, closely related to the tiger salamander. Although the axolotl is colloquially known as a "walking fish", it is not a fish, but an amphibian. The species originates from numerous lakes, such as Lake Xochimilco underlying Mexico City. Larvae of this species fail to undergo metamorphosis, so the

Description 7

A. mexicanum, also known as the Mexican Axolotl, is a long, cylindrical salamander, reaching lengths of about 30 centimeters (12 inches). A neotenic salamander, its most notable physical feature is its gills, which protrude from the back of its wide head and remain there throughout adulthood. Its legs are short. It has four fingers on each of its front legs and five toes on each of its back legs. In the wild, its coloration is dark, but an albino variety has been bred in captivity (Utah's Hogle Zoo 2003).

Sierra madre de oaxaca pine oak forests habitat 8

This taxon is found in the Sierra Madre de Oaxaca pine-oak forests, an ecoregion of northern Oaxaca, Mexico exhibiting a large number of endangered species, so that the conservation value is outstanding in terms of uniqueness of the habitat. The Sierra Madre de Oaxaca pine-oak forests is within the Tropical and Subtropical Conifer Forests biome, and the ecoregion is known for elevated plant endemism, especially within the Sierra de Juarez montane forests.

This ecoregion is located in northern Oaxaca State, and is delineated by the Sierra Norte de Oaxaca Mountains, which have characteristically abrupt and rugged topography. Its tallest peak is Zempoaltepetl (3400 metres), and most of the terrain in this area is above 1000 metres. Three mountain chains or sierras constitute the Sierra Madre de Oaxaca: Juarez, Aloapaneca and Zempoaltepec. The climate is temperate and humid with annual temperatures ranging from 16°C to 20°C. The annual mean precipitation varies greatly from 700 millimetres (mm) to as great as 4000 mm.

The forests also exhibit a high diversity of amphibians, including: the endemic Acultzingo Pigmy Salamander (Thorius dubitus EN), known only from the type locality near Puerto del Aire near Veracruz; the endemic Claw-toed False Brook Salamander (Pseudoeurycea unguidentis CR), known solely from Cerro San Felipe /Cerro San Luis in north-central Oaxaca; the endemic Lower Cerro Pygmy Salamander (Thorius pulmonaris EN), known only from Cerro San Felipe region, central Oaxaca; MacDougal's Pygmy Salamander (Thorius macdougalli VU); and the endemic Mexican Axolotl (Ambystoma mexicanum CR), found in Lakes Chalco and Xochimilco of the Valley of Mexico near Mexico City; the near-endemic Sierra Juarez Moss Salamander (Cryptotriton adelos EN); the endemic Schmidt's Pygmy Salamander (Thorius schmidti EN), known only from near the village of Zoquitlán in southern Puebla, Mexico; and the endemic Mustache False Brook Salamander (Pseudoeurycea mystax EN).

The Sierra Juarez Spiny Lizard (Sceloporus cryptus) is endemic to the ecoregion, and limited in range to drier parts of the Sierra de Juarez, in northeastern Oaxaca. There are a number of threatened reptilian taxa in the ecoregion including the Ribbon Graceful Brown Snake (Rhadinaea fulvivittis VU), a limited distribution snake endemic to southern Mexico.

Avian taxa found here include the Dwarf Jay (Cyanolyca nana EN), Bearded Tree Quail (Dendrortyx barbatus CR), Tamaulipas Pygmy-owl (Glaucidium sanchezi) and Grey-barred Wren (Campylorhynchus megalopterus) as restricted-range bird species, which includes this ecoregion. The Oaxaca Sparrow (Aimophila notosticta NT), Golden-cheeked Warbler (Dendroica chrysoparia EN), Russet Nightingale-thrush (Catharus occidentalis), Hooded Yellowthroat (Geothlypis nelsoni), and Collared Towhee (Pipilo ocai) are also species which thrive in the habitats offered by this mountainous ecoregion.

This ecoregion presents a mosaic of vegetatative associations, due to the varied climate and topography. These formations include tropical evergreen forest, montane cloud forest, pine forest, pine-oak forest, and oak forest. The pine forests, at elevations between 1600 and 2600 metres (m), include trees that are 25 to 40 m tall. Dominant pine species are Mexican White Pine (Pinus ayacahuite); Lawson's Pine (P. lawsonii), a Mexican endemic; Chiapas White Pine (P. strobus var. chiapensischiapensis); Michoacan Pine (P. devoniana LR/LC) and Smooth-barked Mexican Pine (P. pseudostrobus). These pine forests have a robust understory and an herbacious layer dominated by numerous species of the Ericaceae family.

Communication and perception 9

Axolotls communicate mainly via visual cues and chemical cues during mating. At other times of the year there is little to no intraspecific communication.

Axolotls can detect electrical fields and also use their vision and chemical cues to perceive their environment and discover prey.

Communication Channels: visual ; chemical

Other Communication Modes: pheromones

Perception Channels: visual ; chemical ; electric

Development 10

A. mexicanum is paedomorphic, which means that it retains larval characteristics in the reproductively mature adult form. Juvenile and adult axolotls possess feathery, external gills and tail fins suited to an aquatic lifestyle. Metamorphosis can be induced in axolotls via thyroid hormone injections. In the wild, axolotls rarely, if ever, metamorphose.

Development - Life Cycle: neotenic/paedomorphic; metamorphosis

Lifespan/longevity 11

Expected laboratory longevity is 5 to 6 years; however, some animals have been known to live as long as 10 to 15 years. Most laboratory animals die shortly after metamorphosis.

Range lifespan
Status: captivity: 15 (high) years.

Average lifespan
Status: captivity: 5 - 6 years.

Typical lifespan
Status: captivity: 6 (high) years.

Iucn red list assessment 12


Red List Category
CR
Critically Endangered

Red List Criteria
B2ab(iii,v)

Version
3.1

Year Assessed
2010

Assessor/s
Luis Zambrano, Paola Mosig Reidl, Jeanne McKay, Richard Griffiths, Brad Shaffer, Oscar Flores-Villela, Gabriela Parra-Olea, David Wake

Reviewer/s
Global Amphibian Assessment Coordinating Team (Simon Stuart, Janice Chanson, Neil Cox and Bruce Young)

Contributor/s

Justification
Listed as Critically Endangered because its Area of Occupancy is less than 10km2, its distribution is severely fragmented, and there is a continuing decline in the extent and quality of its habitat and in the number of mature individuals.

History
  • 2006
    Critically Endangered
    (IUCN 2006)
  • 2006
    Critically Endangered
  • 2004
    Vulnerable
  • 1996
    Vulnerable
  • 1994
    Rare
    (Groombridge 1994)
  • 1990
    Rare
    (IUCN 1990)
  • 1988
    Rare
    (IUCN Conservation Monitoring Centre 1988)
  • 1986
    Rare
    (IUCN Conservation Monitoring Centre 1986)

Conservation status 13

The natural habitat of A. mexicanum is nearly gone. Historically, they have been known to live in high altitude lakes near Mexico City. Lake Chalco is gone completely, drained for drinking water, and Lake Xochimilco is now nothing more than a scattering of canals and swamps. Because known populations are few and far between, very little is known about the ecology and natural history of A. mexicanum; there have been few ecological studies on wild populations.

CITES: appendix ii

IUCN Red List of Threatened Species: critically endangered

Threats 14

Major Threats

The desiccation and pollution of the canal system and lakes in Xochimilco and Chalco, as a result of urbanization, as well as the traditional consumption of the species by local people, is threatening the survival of this species. Increased tourist activity is poorly regulated and adds further pollution (Zambrano, 2006). The species is also captured for medicinal purposes. The harvesting is targeted at animals that are less than one year old. It was formerly also captured for the international pet trade, although probably all animals in the international trade are now of captive origin. Introduced fishes (tilapia and carp) have increased to high abundances (a recent study collected 600kg of tilapia in one small channel using a 100m net) and have also impacted axolotls through competition and predation. The animals are also being affected by disease, probably spread by invasive species, and as a result of poor water quality. Although the water regime has changed in the last 10 years, and it is reported that pollution levels are decreasing, factors such as very high levels of bacterial contamination could still pose a serious threat.

Sources and Credits

  1. (c) Lokilech, some rights reserved (CC BY-SA), https://upload.wikimedia.org/wikipedia/commons/thumb/0/00/Axolotl_ganz.jpg/460px-Axolotl_ganz.jpg
  2. (c) Biopix, some rights reserved (CC BY-NC), http://www.biopix.com/photos/Ambystoma-mexicanum-00003.JPG
  3. (c) Biopix, some rights reserved (CC BY-NC), http://www.biopix.com/photos/Ambystoma-mexicanum-00008.JPG
  4. (c) Biopix, some rights reserved (CC BY-NC), http://www.biopix.com/photos/Ambystoma-mexicanum-00013.JPG
  5. (c) Biopix, some rights reserved (CC BY-NC), http://www.biopix.com/photos/Ambystoma-mexicanum-00012.JPG
  6. (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Ambystoma_mexicanum
  7. (c) AmphibiaWeb © 2000-2011 The Regents of the University of California, some rights reserved (CC BY), http://eol.org/data_objects/23849563
  8. (c) C. Michael Hogan & World Wildlife Fund, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/27026982
  9. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/18632011
  10. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/18632008
  11. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/18632010
  12. (c) International Union for Conservation of Nature and Natural Resources, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/30928897
  13. (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/18632017
  14. (c) International Union for Conservation of Nature and Natural Resources, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/30928901

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