Amphibians

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.

Taylor’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 on 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.

Taylor’s salamander may be specialised for life in saline (or salty) water, as the salinity of the Laguna Alchichica is near to the maximum tolerated by most adult amphibians, and is well above that tolerable to eggs and embryos. In captivity, Taylor’s salamander survived longer in water salinities similar to Laguna Alchichica – it therefore seems as though this species is somewhat dependent upon a high salt concentration in the water which it inhabits.

An Ambystomatid or mole salamander found only in the Laguna Alchichica in eastern Puebla, Mexico at an elevation of 2,290m above sea level. Mole salamanders are medium to large, stocky amphibians, 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).

Like all neotenic Ambystoma species, Taylor's salamander retains its larval features into adulthood. Taylor's salamander is moderately sized, with a typical length of 150-200mm. Being a neotenic species, it retains its caudal (or tail) fin and external gills into adulthood, never undergoing a complete metamorphosis. Taylor's salamanders are yellowish in colouration, with dark spots along their backs and the upper surface of their tails. They have relatively short, thick external gill stalks. Their heads are quite large, and their limbs underdeveloped, as is the case in most neotenic Ambystoma or “neotenes”.