Histology and ultrastructure of the gut of the tilapia (Tilapia spp.), a hybrid teleost.

The morphology of the intestine has been studied in a species of warm water fish, Tilapia spp., a hybrid teleost of notable economic importance. Light and electron microscope results show that the intestine is a relatively undifferentiated muscular tube lined with a simple columnar epithelium interspersed with goblet cells. The proximal region has a greater surface area, manifested by elongated mucosal ridges. The enterocytes are covered apically with uniform microvilli and exhibit the typical ultrastructural features of pinocytosis, namely extensive invaginations of the luminal plasma membrane and massive accumulation of vesicles in the apical cytoplasm. The distal intestine mucosa is thinner and less elaborately folded and consists of columnar cells with shorter and sparser microvilli. Their supranuclear cytoplasm contains abundant clear vacuoles. Numerous endocrine cells can also be seen. Regional cellular ultrastructural features are correlated with digestive functions.