They retain their larval characteristics throughout adulthood – a phenomenon known as neoteny – reaching sexual maturity in the late larval stage. Adult Lake Pátzcuaro salamanders have developed legs, but also external gills. Visitors can admire seven of these rare salamanders at Hellabrunn Zoo. The peculiar-looking salamanders retain the appearance of a larva throughout their adult life. But in terms of size, they can grow up to 35 cm in length. Two larval features retained are particularly striking: a strong, laterally flattened tail and large external gills. Lake Pátzcuaro salamanders can also breathe through their lungs and skin.
The Lake Pátzcuaro salamander is listed as critically endangered. The species is only found in one lake, Lake Pátzcuaro in the highlands of Mexico, and nowhere else in the world. Previously overfished by local fishermen, its natural habitat is now threatened by pollution. The amphibians are olive in colour, with almost no markings, but may sometimes occur lightly stippled. In contrast to its light belly, the tips of the toes on the front and rare legs are rather dark and may even occur completely black. The external gills are easy to spot thanks to their reddish-brown colour.
Unique partial metamorphosis
Lake Pátzcuaro salamanders are called "eternal infants" due to their appearance. However this is not quite accurate. While they retain some typical larval characteristics such as external gills, swimming tail and regenerative ability of the legs, the rest of the body undergoes metamorphosis as it grows up. Organs such as lungs, skin pigments, as well as oral epithelium and teeth continue to develop.
Lena Bockreiss, curator at Hellabrunn Zoo, has been observing the seven salamanders since their arrival and discussed their progress with the keepers: “All the animals are doing very well. They have quickly settled into their new home and despite their small size have a very big appetite. Our visitors will be thrilled to discover that they resemble the well-known axolotl. However, our Lake Pátzcuaro salamanders are larger, have a bulkier head and granular skin.
Conservation and breeding at a convent
The nuns at a convent by the high-altitude lake have been caring for Lake Pátzcuaro salamanders, known locally as achoque, for over a century. Over time, the Mexican nuns noticed that the amphibians, which they relied on to make cough syrup, were becoming increasingly rare. In 2009, an in-situ species protection initiative, the "PIMVS JimbaniTzipekua", was launched and now maintains a breeding station for the highly endangered Lake Pátzcuaro salamanders.
Zoo director, Rasem Baban, is pleased with the international measures implemented to save the species: "Studies in 2000 and 2010 show that there are no longer any free-ranging salamanders in Lake Pátzcuaro, which of course is very sad. We are therefore delighted to have the opportunity to participate in the Citizen Conservation breeding programme. Like Hellabrunn Zoo, this initiative contributes to the conservation of endangered species.”
Citizen Conservation is a community conservation breeding programme that provides information on breeding and husbandry conditions. The initiative supports a network of people from zoos, science and civil society in saving endangered species through conservation breeding. Further information on the joint initiative of the VdZ (Association of Zoological Gardens), Frogs & Friends and the DGHT (German Society for Herpetology and Terrarium Science) is available at https://citizen-conservation.org/.