Mountain Stream Siredon
(Ambystoma altamirani)
The mountain stream siredon belongs to the family Ambystomatidae, or “the mole salamanders”, which diverged from all other salamanders in the Early Cretaceous period over 140 million years ago. This is around five million years before the koala and dolphin lineages diverged from their common ancestor. It occurs in isolated populations on high mountains to the south and west of the Valley of Mexico in the central state of México, southern Distrito Federal, and northwestern Morelos, Mexico. Now categorised as Critically Endangered, the forest and streams which it inhabits urgently need conserving to secure its survival before it falls victim to extinction.
Urgent Conservation Actions
Effective conservation of the forest and streams within the mountain stream siredon’s range.
Central Mexico
The family Ambystomatidae is also referred to as the mole salamanders because many live in burrows for much of their lives. They are found only in North America (from Canada down to Mexico), the majority (as is frequently seen in the mountain stream siredon) metamorphose from aquatic larvae to become terrestrial adults that are rarely seen except in breeding season, when they migrate to ponds to mate and deposit eggs.
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.

The mountain stream siredon, like many of its close relatives, is a metamorphosing species of mole salamander. It therefore develops into an adult form, losing its larval characteristics such as gills and fins, and developing adult traits such as eyelids and functioning lungs. It returns to ponds in order to breed. Although metamorphosis is externally complete, in the wild some adults remain in the stream with the larvae all year-round, never venturing into the surrounding terrestrial habitats. One theory for why this species may not become terrestrial as an adult is that species evolving in pools surrounded by hostile terrestrial environments develop and retain 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.
The mountain stream siredon is an Ambystomatid or mole salamander from high elevations (2,700-3,200m above sea level) along the Valley of Mexico. Mole salamanders are medium to large, stocky salamanders, 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, partly due 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).

The mountain stream siredon is a metamorphosing variety of mole salamander, which means it develops from an aquatic juvenile form with larval characteristics to a physical form with adult features. Post-metamorphosis adults may sometimes remain in their aquatic environment year-round, despite the fact that the adults lose their gills and fins. This species is fairly small, growing to a length of about 115 mm, including the tail which is around 50 mm long. The tail is greatly compressed and slender, with a low fin running along the top and an even smaller one underneath. The limbs are also slender, with slightly flattened digits. The dorsal (or upper) surface and the sides of the body and tail area are uniform purplish-black in this species, and the underside is purplish-lavender. The chin and lower surfaces of the limbs are partly clouded with a light lavender hue. The edges of the lips, tips of the digits and the narrow ventral fin on the underside of the tail are a dirty-whitish or cream colour.
Like all mole salamanders, the mountain stream siredon has an aquatic larval stage. Larvae undergo metamorphosis to develop into the adult form, losing their gills and fins and becoming capable of living out of water. However, it has been recorded that both adults and larvae remain in streams year-round, although what percentage of the adult population exhibit this behavior is unknown. Other adults will leave the aquatic environment to begin a terrestrial (or ground-dwelling) life, returning to water bodies to breed.

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.
The siredon lives and breeds in small, permanent streams flowing through high-elevation pine or pine-oak woodlands. It has also been found in streams in cleared pastures. Terrestrial metamorphosed adults occur adjacent to streams flowing through these forests and are also found in pasture land.
Occurs in isolated populations on high mountains to the south and west of the Valley of Mexico in the central state of México, southern Distrito Federal, and northwestern Morelos, Mexico. The known populations include Lagunas de Zempoala, Ajusco Mountain and Desierto de los Leones, although it has also been found in some additional sites. Its altitudinal range is 2,700-3,200 metres above sea level.
Population Estimate
Formerly common, with larvae present in most small streams within its range. The population now appears to be greatly reduced, although new field surveys are urgently needed to assess declines that are likely to have occurred in the last 15 years.
Population Trend
The IUCN Red List of Threatened Species indicates that the mountain stream siredon’s total population size is generally in decline.
Listed as Critically Endangered on the IUCN Red List of Threatened Species due to its serious population decline, estimated to be more than 50% over the last three generations, inferred from the extent of habitat degradation and a sharply decreased number of records of wild individuals. Its extent of occurrence is less than 5,000 km sq. and its area of occupancy is less than 500 km sq., its distribution is severely fragmented and there is continuing decline in the number of mature individuals and in the extent and quality of its habitat around the Valley of Mexico.
The forest and stream habitat in the vicinity of Mexico City where the mountain stream siredon lives has been severely altered, leading to a greatly degraded habitat. Illegal logging in National Parks, very heavy recreational tourism, stream pollution and sedimentation, and stream diversion have all been significant negative impacts reducing the quality of habitat for this species. Introduced predatory fishes (trout and others) have eliminated the species from many streams, and local consumption for food may also be an issue.
Conservation Underway
This species occurs, or used to occur, in three National Parks: Lagunas de Zempoala, Ajusco Mountain, and Desierto de los Leones. Surveys conducted in the 1970s and 1980s still found it to be present in Ajusco and Desierto de los Leones, but absent from Lagunas de Zempoala. This species is protected under the category Pr (Special protection) by the Government of Mexico.
Conservation Proposed
Effective conservation of the forest and streams of the mountain stream siredon is an urgent priority. An assessment of the conservation status of the species is required to determine where it is still present and what the overwhelming threats to its survival are in each area. A conservation action plan may then be compiled to indicate how best to address these issues. Captive breeding for potential re-introduction of the mountain stream siredon should also be investigated and attempted. This would involve creating a breeding colony maintained outside of its natural habitat, giving rise to individuals from the species that are sheltered from problems associated with their situation in the wild. This can be located within the species’ range or in a foreign country that has the facilities to support a captive breeding programme for that species. It may be possible to breed the mountain stream siredon in captivity and reintroduce them into the wild, in which case captive animals could be a source of new individuals to repopulate natural habitats whilst its ecosystem is restored and an environmental management plan is developed for the species and its habitat.
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