A microscopic and microanalytical study (Fe, Ca) of the teeth of the larval and juvenile Ambystoma mexicanum (Amphibia: Urodela: Ambystomatidae)

We studied the teeth of larvae and one juvenile of the axolotl Ambystoma mexicanum, a urodele species that undergoes partial metamorphosis, by light microscopy of ground sections, backscattered electron imaging and semi-quantitative microanalysis in the scanning electron microscope. By applying these techniques it was possible to identify enamel, enameloid and dentin in the teeth. Iron was found to be present in enamel and enameloid, the concentrations being highest in the enamel. A staining indicative of the presence of iron was observed in the inner dental epithelium of tooth germs. Dentinal tubules mostly followed a straight course, but some recurved over a short distance distally. In larval teeth and teeth of “larval type” in the juvenile individual the dentinal tubules ended in the basal portion of the enameloid. Our results show that in the axolotl, monocuspid teeth of the “larval type” that developed after partial transformation still possess an enameloid layer beneath a thin enamel cap. The findings of the present study are consistent with the view that enameloid matrix is secreted by odontoblasts, while enameloid maturation is (largely) controlled by ameloblasts.