Endemic only to the swamps around Mexico City, the endangered axotlotl is used around the world to study nerve regeneration
Ambystoma mexicanum, a salamander found only in the fetid canals surrounding Mexico City, faces extinction despite the efforts of researchers. As reported by Robert Koenig in the 5 December issue of Science, ecologists estimate that there are now only 100 of these salamanders per square kilometer in the canals, swamps, and lakes around the city – a rapid drop from their density of 600 per square kilometer in the 1980s. The population has dwindled as the system of waterways has dried up and become more polluted, and the salamander is now designated as critically endangered by the International Union for the Conservation of Nature (IUCN). Luis Zambrano of the National Autonomous University of Mexico is studying the axolotl to better understand its ecology, reproduction, and conservation. He’s working to identify the best areas of habitat and establish reserves.
Known locally as the axolotl, the salamander is named after an Aztec god. Its most noticeable feature are its gills, which it keeps from it larval stage. The Aztecs used the foot-long amphibians for medicine. Modern researchers are hoping the axolotl can contribute to our understanding of nerve re-generation. Like other salamanders, the axolotl can regenerate its tail and legs, and re-connect its nervous system. Unlike other salamanders, the axolotl is easy to raise in the lab and has been studied by scientists for over 100 years. Nerve and spinal injuries are normally devastating and irreparable in vertebrates. The axolotl’s easy-going nature in the lab makes it the perfect subject for studying how nerves grow and heal.
While the axolotl will continue to survive in captivity, Science reports that researchers are worried that important genetic variation will be lost if it goes extinct in the wild. Populations of lab animals are in-bred and have lost genetic diversity. Studying wild salamanders would allow researchers to examine how natural genetic variation affects the species’ biology. The extinction of the wild ancestors of domesticated organisms is currently a major concern for researchers, especially in agriculture.
Worryingly to scientists even lab animals may not be safe. Since the 1990s, a mysterious disease has been killing larvae in some labs.
It is commonly argued that biodiversity should be conserved because of the unknown benefits animal and plant species may have for humans. Common temperate plants such as willow and Pacific Yew have yielded powerful drugs like aspirin and the anti-cancer drug taxol. Other ecosystems could therefore be full of medical surprises. In the case of the axolotl, we may watch a species that is already paving dividends to Homo sapiens slip away.
Current work by Dr. Zambrano:
A population matrix model and population viability analysis to predict the fate of endangered species in highly managed water systems. L. Zambrano, E. Vega, L. G. Herrera M., E. Prado, V. H. Reynoso. Animal Conservation Volume 10, Issue 3, August 2007, Pages: 297-303.