The Mexican axolotl salamander resists disappearing in Xochimilco

The Mexican axolotl salamander is a urodele amphibian; it has a tail, both in the larval stage and in adulthood, and has four legs. The most important thing is that 22 species live in Mexico, 17 of which are endemic to the country, mainly in the Neovolcanic Axis.

The Mexican axolotl salamander resists disappearing in Xochimilco
The Mexican salamander retains millenarian characteristics of salamanders but is closer to frogs and toads. Image: Semarnat

The ecological disaster in the canals and the increase in temperature are reducing populations of the salamander. An international project seeks to restore the amphibian's ecosystem and its interaction with other organisms. In the area, there is an excess of invasive species, such as tilapia and carp.

Although the Xochimilco salamander (Ambystoma mexicanum) is locally limited, it cannot be said that this species is about to disappear, because there is still genetic material and organisms in laboratories that are used for research and reintroduction in this area, said Diego Chaparro Herrera, a researcher at the Environmental Microbiology Laboratory of the Faculty of Higher Education (FES) Iztacala.

The university academic participates in the research project "Management and identification of key problems in selected sites for the sustainable reintroduction of the salamander 2019-2022", which seeks to restore the ecosystem in which it develops and the interactions it has with other organisms, for example with zooplankton, phytoplankton, and macrophytes, to modify the quality of aquatic systems.

As part of the research, funded by Earthwatch Institute, EY (U.S. environmental organizations), and REDES (Ecological Restoration and Development), the project provides advice to the farmers through workshops on how to grow their vegetables and ornamental plants using a more organic approach. In addition, these associations share with their marketing strategies for the proper and fair commercialization of their products to obtain higher income.

They also provide them with resources, such as the complete installation of dry or ecological toilets, so that waste is not deposited in the aquatic systems; and they also teach them how to use this waste in the cultivation of their ornamental plants, such as marigolds and poinsettias. This is gratifying: we conserve the environment in Xochimilco and can begin to work on reintroduction, emphasized Chaparro Herrera.

It is a urodele amphibian; that is, it has a tail, both in the larval stage and in adulthood, and has four legs. The most important thing is that 22 species live in Mexico, 17 of which are endemic to the country, mainly in the Neovolcanic Axis: the states of Veracruz, Puebla, Tlaxcala, Hidalgo, Mexico, Queretaro, Michoacan, and Mexico City.

Due to its cultural and scientific importance, besides being the protagonist of multiple national and international types of research, as well as of museums in our nation, books, art, or emojis, its image was included in the new Mexican 50 peso bills. It even became a popular mascot in various parts of the world.

However, the ecological disaster in the canals of Xochimilco, in particular, and the increase in temperature due to climate change, are destroying the populations of these species, which reproduce in the cold months, although climate variations affect them substantially.

The FES Iztacala researcher explained: "We have seen that it is already difficult to reproduce them in the laboratory, so we must transfer some adult organisms of Ambystoma mexicanum to the north of the State of Mexico (Tepotzotlán) in the community of Cañada de Cisneros, in the Axolo-Tlali center, where the climate is a little colder and the water quality improves; however, the salamander of Xochimilco is not from that area".

Tepotzotlán is a region far from its natural habitat and it is observed, for example, that this organism maintains a constant bacterial flora. However, in Xochimilco, this microbiota kills them because the increase in temperature in their natural habitat causes an exponential growth of bacteria in them.

The salamander used to control the excessive growth of phytoplankton in Xochimilco, but today it faces the destruction of the food web due to the excess of invasive species (tilapia and carp, for example) and the contamination of the water in its canals, which almost completely wiped out the amphibian populations when competing for food and niche. "We see it reflected in the large amount of green color that we have in this aquatic system".

There is no one to regulate this pollution, he said, so we have reached this effect called eutrophication of the aquatic system, which destroys its aesthetics and water quality. "More than 18 years working with the salamander have led me to understand that much has been done to safeguard this species, but much more is still required: regulating water quality and invasive species, among other factors. Even the very presence of the inhabitants of Mexico City influences affect the salamander of Xochimilco," warned the university specialist.

Tlatoanis of Xochimilco

As part of their collaboration with the Environmental Analysis Laboratory of the Faculty of Sciences and the organizations Earthwatch Institute, EY, and REDES, they went to exclusive areas of San Gregorio Atlapulco, a town originally from Xochimilco, where they found some wild organisms -which they called tlatoanis because they are pureblood-, which have not mixed with other populations, which is a big problem.

That is to say, in the colonies at the laboratories of FES Iztacala, Facultad de Ciencias, Xochimilco, Universidad Autónoma Metropolitana, Chapultepec, etc., a great inbreeding prevails, which originates a genetic recombination that also contributes to the loss of the salamander.

As a consequence, there are vulnerable, genetically weak species. For example, the albino or "rosita", which is reproduced to be sold as a pet, although genetically it is not viable, nor is it used for laboratory experiments. It even runs the risk of being preyed upon because of its striking color. "For us, this affectation is precisely a genetic recombination between relatives".

It is difficult to determine the number of salamanders per square meter in the colonies. "We have them per aquarium, and in those of 40 liters, for example, there are up to four organisms; while in a natural environment, in a fishing process from eight in the morning to three in the afternoon, with a chinchorro (fishing technique with nets) you can catch up to six tons of carp and tilapia, against one, two or zero salamanders".