Organisation of the palate in a spontaneously transforming Mexican axolotl (Ambystoma mexicanum): a case report

We describe the organisation of the palate in a specimen of the Mexican axolotl (Ambystoma mexicanum), which spontaneously started metamorphosis in an advanced age after several breeding cycles, but had not yet completed transformation at an age of > 7 years when it was euthanized. The palate shows a mosaic of paedomorphic (absence of the edentate vomerine plate, monocuspid pedicellate teeth) and transformed traits (separation of palatine and pterygoid, fusion of the vomer and anterior parts of the palatine (vomeropalatinum), bicuspid teeth at least on the upper jaw). The vomeropalatinum has a broad pars palatina along its inner side (typical for paedomorpic specimens). We think that the transformation process has started after the specimen has reached the full paedomorphic status.