Fine Structure of the Lingual Dorsal Surface of the Bullfrog

Scanning electron microscopy was used to investigate the ultrastructure of the lingual dorsal epithelial cells and sensory organs of the bullfrog. The specimens were prepared by a method involving osmium post-fixation and acid-treatment to remove extracellular material adhering to the surface of the tongue.Over almost the entire dorsal surface except the anterior margin and posterior protrusions, filiform papillae consisting of a large number of non-ciliated cells with microridges and a small number of ciliated cells were compactly distributed, while fungiform papillae were scattered among these filiform papillae. A round sensory disk was located on the top of each fungiform papilla. The surface of the disk was widely covered with a honeycomb structure, and a small number of cells with microvilli on their surfacewere scattered amongst the honeycomb structure. Each sensory disk was encircled by a ciliated cell band.