The epithelium of the tongue of Ambystoma mexicanum - Ultrastructural and histochemical aspects

The distribution pattern of taste buds and goblet cells and histochemical a nd ultrastructural aspects of the tongue epithelium of Ambystoma mexicanum are here described. This study is also concerned with the developmental sta ges and origins of the epithelial cells. Pavement cells and goblet cells of the stratum superficiale are replaced by basal cells of the stratum germin ativum in larvae and neotenous adults. The pavement cells of the larvae are characterized by a marginal layer of mucin grana. Decompaction of the muci ns occurs immediately before extrusion in the adult. The larval goblet cell type (tppe I), which is also present in the adult, contains unfused grana of irregular shape. At the tip of the tongue, a further type (type II) of g oblet cells is found. In the type II cells the intracellular secretory gran a fuse to a single homogeneous mass. Leydig cells of the tongue epithelium are discerned by light microscopy first in the semi-adult, apparently corre lated with partial metamorphosis. In the course of ontogenesis and induced metamorphosis the secretion changes to neutral glycoconjugates. The mucins of the pavement cells change first followed by those of the goblet cells. T he glands of the secondary tongue show a dorso-ventral pattern of varying s ecretory qualities. Taste buds are found at the anterior margin of the tong ue and along the base of the gill clasps in the early larva. They are alrea dy distributed all over the tongue at the end of the early larval phase.