7.
Leora's Stream Salamander
(Ambystoma leorae)
CR
Overview
The family Ambystomatidae or “the mole salamanders” diverged 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. Leora’s Stream Salamander appears to be confined to the upper tributaries of the Balsas River, central Mexico. Conservation and restoration of this habitat is an urgent priority in order to save this species from extinction in the future.
Urgent Conservation Actions
Establish clearly protected areas and sensitive land use techniques; control of introduced predatory fish populations.
Distribution
Central Mexico
Fact
Rhyacosiredon used to be considered a separate genus within the family Ambystomatidae. However, further analysis of the family tree of the mole salamanders found that members of the genus Rhyacosiredon were in fact more closely related to certain members of the genus Ambystoma than other Ambystoma species were to each other. Leora’s stream salamander was among the three species moved from Rhyacosiredon to Ambystoma.

The initial misclassification of these salamanders into a separate genus was probably due to the stream-type physical form of both the larvae and neotenes (or adult individuals with a perpetual juvenile appearance). The former members of the genus Rhyacosiredon that were moved into Ambystoma all have short gills and thicker “gular” folds (membranous folds of skin across their throats), which are now thought to be simply adaptations to a different habitat type within the Ambystoma group.

The family Ambystomatidae is also referred to as the mole salamanders because many live in burrows for much for their lives. They are found only in North America (from Canada down to Mexico), the majority (like Leora’s salamander) metamorphose from aquatic larvae to become terrestrial adults that are rarely seen except in the 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.

Leora’s stream salamander, 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. Unlike some metamorphosing mole salamanders that become terrestrial in adult life, Leora’s stream salamander remains in the water. 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 safely of their watery home. This is a common trait in species that inhabit high-elevation ponds.
Description
Leora’s stream salamander is an Ambystomatid or mole salamander known only from Guadalupe, 14km east of San Martín in north-western State of Mexico at an elevation of 2,500 meters above sea level. 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. 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).

Leora’s stream salamander 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. The post-metamorphosis adult phase of this species is also aquatic, despite the fact that adults lose their gills and fins. This species grows to a total length of around 150-200mm, with the long tail accounting for over half of this measurement. Eleven distinct costal grooves are visible in the skin along either side of the body. The colouration of the species is olive to grey-green on the head and back, with a tail that is mottled with greyish and tan cream shades. The ventral surface (or underside) is a dirty cream colour. The dorsal (or upper) surfaces of the body, head and limbs are strongly spotted with dark brown.
Ecology
A metamorphosing variety of Ambystomatid or mole salamander, which means it develops from the aquatic larval form to an adult body shape during its lifetime. However, unlike some of the metamorphosing varieties of mole salamander, Leora’s stream salamander remains in the stream when it is an adult and does not become terrestrial (or ground-dwelling).

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.
Habitat
Leora’s stream salamander requires the presence of shallow water in streams and humid pine forest areas for breeding. One known breeding site is in a stream next to a major road.
Distribution
Known only from around Río Frio town, in the State of Mexico close to the borderline with Puebla in central Mexico, at around 3,000m above sea level. Here it appears to be confined to the upper tributaries of the Balsas River. The species has not been found in the locality where it was originally discovered for over 30 years, since this area is extremely polluted by the town of Río Frio. However, in 1983 it was still found in three sites in small streams at 9km and 15km to the north-east of Río Frio.
Population Estimate
Formerly relatively common, there appears to have been no reports of Leora’s stream salamander for the last 20 years, although this is probably due to a lack of herpetological work within its range. A population estimate for this species is therefore unknown at present.
Population Trend
No population data is currently available for Leora’s stream salamander, although the population trend is assumed to be in decline in the IUCN Red List of Threatened Species.
Status
Leora’s stream salamander is 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 number of mature individuals and in the extent and quality of its habitat around Río Frio.
Threats
The pollution and desiccation of the breeding streams in the vicinity of Río Frio town, as well as the clearance of pine forests (for grazing and other economic activities), are the major threats to Leora’s stream salamander. The species is also likely to be caught locally for food, and introduced predatory fish in the salamander’s habitat are also a threat to its survival in the wild.
Conservation Underway
Leora’s stream salamander occurs in the Parque Nacional Río Frio, but there is huge recreational disturbance in this protected area, including forest clearance. The species is also protected under the category Pr (Special Protection) by the Government of Mexico.
Conservation Proposed
Conservation and restoration of Leora’s stream salamander habitat is an urgent priority in order to save this species from extinction in the future. In addition to conserving wild habitat for this species, the IUCN Technical Guidelines for the Management of Ex situ Populations, part of the IUCN Red List of Threatened Species, recommend that all Critically Endangered species should have an ex situ population managed to guard against the extinction of the species. An ex situ population is ideally a breeding colony of a species maintained outside its natural habitat, giving rise to individuals from that 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. Further investigation is therefore required into the possibilities of establishing a captive breeding programme for Leora’s stream salamander. Captive breeding is known to be very difficult for coldwater-adapted Ambystoma species, although it is possible and should still be considered.

However, any ex situ conservation measure is rendered ineffective if there remains insufficient natural habitat in which to release captive bred populations in the future. Clearly protected areas, sensitive land use techniques and the control of introduced predatory fish populations are of paramount importance to rescuing this critically endangered mole salamander from extinction in the wild. Forest and stream restoration and the protection of key sites around Río Frio town are therefore the primary actions required for the preservation of the species.
Links
References
AmphibiaWeb: Information on amphibian biology and conservation [web application]. 2006. Berkeley, California: AmphibiaWeb. Available: amphibiaweb. Accessed: 08 December 2006.

Frost, Darrel R. 2006. Amphibian Species of the World: an Online Reference. Version 4 (17 August 2006). Electronic Database accessible at: . American Museum of Natural History, New York, USA.

Frost, D. R., T. Grant, J. Faivovich, R. H. Bain, A. Haas, C. F. B. Haddad, R. O. De Sá, A. Channing, M. Wilkinson, S. C. Donnellan, C. J. Raxworthy, J. A. Campbell, B. L. Blotto, P. Moler, R. C. Drewes, R. A. Nussbaum, J. D. Lynch, D. M. Green, and W. C. Wheeler. 2006. The Amphibian Tree of Life. Bulletin of the American Museum of Natural History 297: 1-370.

IUCN, Conservation International and NatureServe. 2006. Global Amphibian Assessment. Global Amphibian Assessment. Accessed on 08 December 2006.

Obst, F.J., Richter, K. and Jacob, U. 1984. The Completely Illustrated Atlas of Reptiles and Amphibians for the Terrarium. T.F.H. Publication Inc., N.J., U.S.A.

Reilly, S.M. and Brandon, R.A. 1994. Partial paedomorphosis in the Mexican stream salamanders and the taxonomic status of the genus Rhyacosiredon. Copeia. 1994:656-662.

Roelants, K., Gower, D. J., Wilkinson, M., Loader, S. P., Biju, S. D., Guillaume, K., Moiau, L. and Bossuyt, F. 2007. Global patterns of diversification in the history of modern amphibians. Proceedings of the National Academy of Sciences 104: 887-892.

Shaffer, H.B. 1984. Evolution in a paedomorphic lineage. I. An electrophoretic analysis of the Mexican ambystomatid salamanders. Evolution. 38:1194-1206.

Shaffer, H.B. 1984. Evolution in a paedomorphic lineage. II. Allometry and form in the Mexican ambystomatid salamanders. Evolution. 38:1207-1218.

Shaffer, H.B. and Lauder, G.V. 1985. Patterns of variation in aquatic ambystomatid salamanders: kinematics of the feeding mechanism. Evolution. 39(1):83-92.

Shaffer, B., Parra Olea, G. & Wake, D. 2004. Ambystoma leorae. In: IUCN 2006. 2006 IUCN Red List of Threatened Species. IUCN Red List of Threatened Species. Downloaded on 08 December 2006.

if you can provide new information to update this species account or to correct any errors, please email us at info@edgeofexistence.org


Forum comments

There are as yet no comments for this species.

Add a comment

You must log in to post. If you don't have a login, it's easy to register.