Salamander

Axolotls are Mexican salamanders which look like large tadpoles with four legs and a necklace of feathery gills. In the 16th century, the explorer Hernan Cortes first described them as living in the lakes near Mexico City; but today the city has engulfed their natural habitat, and they are an endangered species in the wild. They do, however, happen to live and grow very well in the laboratory.

Salamanders and newts, their close relatives, have long been the subjects of biological study because they are among the rare vertebrates that can replace lost limbs and successfully regenerate nerves.

But it is the embryonic heart of the axolotl that interests cardiology researchers, who remove from 3- or 4-day-old embryos tiny specks of tissue that are designed to form the heart. By placing these specks of tissue in a salt solution and adding various growth factors, researchers make it possible for these cells to divide, develop into full-fledged heart cells, and start to beat. The study of these cells has important implications for the millions of people worldwide who suffer heart attacks.