Ambystoma mexicanum, the Mexican axolotl
This is Ambystoma mexicanum, the Mexican axolotl. As with Xenopus, Ambystoma live their entire lives in an aquatic environment. They provide a good example of neotyny, i.e., the acqusition of reproductive maturity without passing from the larval stage to the adult. Remarkably, Ambystoma can be induced to complete metamorphosis under a variety of conditions, including certain environmental stresses and treatment with thyroid hormone. The extremely large size of their eggs makes them convenient for use in undergraduate laboratories. Indiana University still maintains an axolotl colony; their collection includes several mutant lines.