On the ultrastructure and permeability of taste buds of the marine teleost Ciliata mustela.

The abundant taste buds of the barbels and free fin rays of the five bearded rockling, Ciliata mustela contain an average of 100-150 cells, falling into two types. Tubule-containing cells ('t-cells'), tentatively identified as receptor cells, and each surrounded by fibril-containing cells ('f-cells') in the central part of the bud. t-Cells also occur in two concentric shells separated by indifferent epithelial cells at the periphery of the bud. f-Cells are characterized by their concentrations of fine fibrils, and by granules or vesicles of 180-190 mmu diameter. The 100 or so receptor cells in a taste bud are innervated by some 250 axons. Lanthanum penetrates more deeply into the extracellular space of taste buds than into the extracellular space of the general epithelium, perhaps indicating that a greater area than the mere protruding tip of receptor cells may be accessible to chemical stimulation. Degenerating cells may provide an important route of entry for such external agents.