An ultrastructural study has been made of gastric mucosa of a teleoste
an fish, Tilapia spp. The cytological features of the surface mucous c
ells, mucous neck cells, glandular cells and endocrine cells are descr
ibed. The surface mucous cells, identified by their superficial locali
zation, are characterized by apical granules. The mucous neck cells ar
e distinguished by the appearance of their mucous granules and their l
ocalization between surface mucous cells and glandular cells. The gast
ric glands contain only one form of cell whose fine structure is simil
ar to cells that secrete hydrochloric acid. Physiological implications
of some ultrastructural features are also discussed.