Anderson’s salamander exhibits some highly unusual and distinct features, indicative of its evolutionary distinctiveness, including its rare “neotenous” life history, whereby the species never develops into an adult but instead retains its juvenile characteristics throughout life, essentially achieving reproductive maturity whilst still in its undeveloped larval form. This would be akin to a tadpole being able to breed without ever turning into a frog. The species is totally aquatic, spending its whole life in the same body of water (Lake Zacapu). This lake is currently suffering from pollution which poses a major threat to the survival of the species.
Evolutionary Distinctiveness
Order: Caudata
Family: Ambystomatidae
The family Ambystomatidae or “the mole salamanders” is included within the four earliest or most primitive family lineages of the order “Caudata” (the salamanders), diverging from all other salamanders in the Early Cretaceous period over 140 million years ago, around five million years before the koala and dolphin lineages diverged from their common ancestor. The small number of species that represent the genus Ambystoma are highly evolutionarily distinct members of both the salamanders and the amphibians as a whole.Anderson’s salamander exhibits some highly unusual and distinct features, indicative of its evolutionary distinctiveness, including its rare “neotenous” life history, whereby the species never develops into an adult but instead retains its juvenile characteristics throughout life, essentially achieving reproductive maturity whilst still in its undeveloped larval form. There are a couple of theories for why neoteny (also referred to as paedomorphosis) develops in some mole salamanders. One idea is that the production or effectiveness of the hormone thyroxine is compromised, either by the species living in water bodies containing insufficient iodine (which is required in the manufacture of thyroxine by the body) or in water temperatures that are too cold for the thyroxine to be effective. This impacts upon the development of the species and sexually mature adults never develop adult characteristics but remain in the larval form. A second theory suggests that species evolving in pools surrounded by hostile terrestrial environments develop aquatic lives to obviate the need to exit the relative safety of their watery home. This is a common trait in species that inhabit high-elevation ponds.
Order: Caudata
Family: Ambystomatidae
The family Ambystomatidae or “the mole salamanders” is included within the four earliest or most primitive family lineages of the order “Caudata” (the salamanders), diverging from all other salamanders in the Early Cretaceous period over 140 million years ago, around five million years before the koala and dolphin lineages diverged from their common ancestor. The small number of species that represent the genus Ambystoma are highly evolutionarily distinct members of both the salamanders and the amphibians as a whole.Anderson’s salamander exhibits some highly unusual and distinct features, indicative of its evolutionary distinctiveness, including its rare “neotenous” life history, whereby the species never develops into an adult but instead retains its juvenile characteristics throughout life, essentially achieving reproductive maturity whilst still in its undeveloped larval form. There are a couple of theories for why neoteny (also referred to as paedomorphosis) develops in some mole salamanders. One idea is that the production or effectiveness of the hormone thyroxine is compromised, either by the species living in water bodies containing insufficient iodine (which is required in the manufacture of thyroxine by the body) or in water temperatures that are too cold for the thyroxine to be effective. This impacts upon the development of the species and sexually mature adults never develop adult characteristics but remain in the larval form. A second theory suggests that species evolving in pools surrounded by hostile terrestrial environments develop aquatic lives to obviate the need to exit the relative safety of their watery home. This is a common trait in species that inhabit high-elevation ponds.
Description
Anderson’s salamander is an Ambystomatid or mole salamander found only in Lake Zacapu near Zacapu, Mexico at an elevation of 2,000 meters above sea level. Mole salamanders are medium to large, stocky salamanders, usually measuring between 90 to 350mm from the tip of the nose to the end of the tail, which salamanders retain throughout their life. Males are often larger than females, owing to their longer tails. Ambystomatids generally exhibit both aquatic “neotenic” larval (or aquatic and permanently juvenile in form with external, feathery gills) and terrestrial “metamorphosed” (or ground-dwelling, fully developed adult in form with reduced gills) stages in their wild populations. Ambystomatids are often boldly patterned as adults, with well-developed “costal” grooves (successive vertical grooves along the sides of the body), especially the metamorphosing varieties. They have a rather flattened body with a wide, flattened head, a large mouth and smooth skin with many glands. The tail is roundish or laterally compressed, and, during the breeding season, males have a very swollen cloacal zone (the region around the reproductory and excretory opening in amphibians located underneath the base of the tail).Like all neotenic Ambystoma species, Anderson’s salamander retains its larval features into adulthood. The mature salamander has medium-sized external gills with bright red filaments, and a prominent caudal (or tail) fin. It grows to a length of around 214 mm, with the tail accounting for about 40% of this measurement. A dorsal fin extends as a low ridge from the base of the gill rakers along the back to the base of the tail, where it rises about 13 mm to form the dorsal tail fin. This species has a large head and small, stocky limbs, as do the larvae. The toes are short and pointed with a slight degree of webbing. The skin colouration is a complex pattern of black blotches (some interconnected) on a red-brown base.
Anderson’s salamander is an Ambystomatid or mole salamander found only in Lake Zacapu near Zacapu, Mexico at an elevation of 2,000 meters above sea level. Mole salamanders are medium to large, stocky salamanders, usually measuring between 90 to 350mm from the tip of the nose to the end of the tail, which salamanders retain throughout their life. Males are often larger than females, owing to their longer tails. Ambystomatids generally exhibit both aquatic “neotenic” larval (or aquatic and permanently juvenile in form with external, feathery gills) and terrestrial “metamorphosed” (or ground-dwelling, fully developed adult in form with reduced gills) stages in their wild populations. Ambystomatids are often boldly patterned as adults, with well-developed “costal” grooves (successive vertical grooves along the sides of the body), especially the metamorphosing varieties. They have a rather flattened body with a wide, flattened head, a large mouth and smooth skin with many glands. The tail is roundish or laterally compressed, and, during the breeding season, males have a very swollen cloacal zone (the region around the reproductory and excretory opening in amphibians located underneath the base of the tail).Like all neotenic Ambystoma species, Anderson’s salamander retains its larval features into adulthood. The mature salamander has medium-sized external gills with bright red filaments, and a prominent caudal (or tail) fin. It grows to a length of around 214 mm, with the tail accounting for about 40% of this measurement. A dorsal fin extends as a low ridge from the base of the gill rakers along the back to the base of the tail, where it rises about 13 mm to form the dorsal tail fin. This species has a large head and small, stocky limbs, as do the larvae. The toes are short and pointed with a slight degree of webbing. The skin colouration is a complex pattern of black blotches (some interconnected) on a red-brown base.
Ecology
Anderson’s salamanders are totally aquatic and spend their whole lives in the same body of water. The species is paedomorphic (or permanently juvenile in physical characteristics), and reaches sexual maturity whilst still having the appearance of a larval salamander. This would be akin to a tadpole being able to breed without ever turning into a frog. It requires a clean, cool aquatic habitat and is found only in Lake Zacapu and the spring-fed streams and canals associated with the lake. Once the eggs are laid in water they are left to develop with no further participation by either parent. This species does not exhibit parental care.Anderson’s salamanders do not metamorphosise from larval to adult form in nature, and individuals that have been artificially induced to metamorphosise with thyroid hormone in the laboratory do not thrive. The diet consists largely of snails and crawfish.
Anderson’s salamanders are totally aquatic and spend their whole lives in the same body of water. The species is paedomorphic (or permanently juvenile in physical characteristics), and reaches sexual maturity whilst still having the appearance of a larval salamander. This would be akin to a tadpole being able to breed without ever turning into a frog. It requires a clean, cool aquatic habitat and is found only in Lake Zacapu and the spring-fed streams and canals associated with the lake. Once the eggs are laid in water they are left to develop with no further participation by either parent. This species does not exhibit parental care.Anderson’s salamanders do not metamorphosise from larval to adult form in nature, and individuals that have been artificially induced to metamorphosise with thyroid hormone in the laboratory do not thrive. The diet consists largely of snails and crawfish.
Habitat
Its habitat is that of Lake Zacapu, a small lake near Zacapu, sitting at an altitude of 2000 meters above sea level. The lake is located within the Mesa Central portion of Mexico, an area home to many neotenic Ambystoma species. Lake Zacapu (or Lago de Zacapu) is temperate, with low salinity, and the Anderson’s salamander inhabits the main body of the lake and the spring-fed streams and canals associated with it, requiring a clean, cool aquatic habitat in order to survive.
Distribution
Lake Zacapu (Lago Zacapu) and its surrounding streams near Zacapu, located in north-western Michoacan within the Mesa Central portion of Mexico at an altitude of 2000 metres above sea level.
Population Estimate
Unknown.
Population Trend
Anderson’s salamander is not currently rare in its small area of occupancy, but it is considered to be in decline by the IUCN Red List of Threatened Species.
Its habitat is that of Lake Zacapu, a small lake near Zacapu, sitting at an altitude of 2000 meters above sea level. The lake is located within the Mesa Central portion of Mexico, an area home to many neotenic Ambystoma species. Lake Zacapu (or Lago de Zacapu) is temperate, with low salinity, and the Anderson’s salamander inhabits the main body of the lake and the spring-fed streams and canals associated with it, requiring a clean, cool aquatic habitat in order to survive.
Distribution
Lake Zacapu (Lago Zacapu) and its surrounding streams near Zacapu, located in north-western Michoacan within the Mesa Central portion of Mexico at an altitude of 2000 metres above sea level.
Population Estimate
Unknown.
Population Trend
Anderson’s salamander is not currently rare in its small area of occupancy, but it is considered to be in decline by the IUCN Red List of Threatened Species.
Status
Listed as Critically Endangered in the IUCN Red List of Threatened Species because its extent of occurrence is less than 100km sq. and its area of occupancy is less than 10km sq., all individuals are in a single subpopulation, and there is continuing decline in the extent and quality of the lake habitat around the city of Zacapu.
Threats
The major threat to the wild population is the pollution of Lake Zacapu, its sole habitat location. Additionally, the animals are heavily fished for food and predatory fish have been introduced into the lake which may pose a severe problem if they prey extensively on the declining populations of Anderson’s salamander.
Conservation Underway
Anderson’s salamander does not occur in any protected area but the species could undergo a population recovery if Lake Zacapu can be kept clean and its ecosystem restored, including the control of introduced predatory fish and general levels of resource extraction from the lake and its associated streams and canals. Studies are needed to evaluate the sustainability of the harvest as well as on the impacts of introduced predatory fish. The species is protected under the category Pr (Special Protection) by the Government of Mexico.
Listed as Critically Endangered in the IUCN Red List of Threatened Species because its extent of occurrence is less than 100km sq. and its area of occupancy is less than 10km sq., all individuals are in a single subpopulation, and there is continuing decline in the extent and quality of the lake habitat around the city of Zacapu.
Threats
The major threat to the wild population is the pollution of Lake Zacapu, its sole habitat location. Additionally, the animals are heavily fished for food and predatory fish have been introduced into the lake which may pose a severe problem if they prey extensively on the declining populations of Anderson’s salamander.
Conservation Underway
Anderson’s salamander does not occur in any protected area but the species could undergo a population recovery if Lake Zacapu can be kept clean and its ecosystem restored, including the control of introduced predatory fish and general levels of resource extraction from the lake and its associated streams and canals. Studies are needed to evaluate the sustainability of the harvest as well as on the impacts of introduced predatory fish. The species is protected under the category Pr (Special Protection) by the Government of Mexico.
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