Abstract

The main stages of the phagocytic process after the intraperitoneal injection of colloidal carbon to tilapia (Oreochromis niloticus), was ultra-structurally documented. Carbon particles were initially in diffuse form in the cytoplasm but they gradually formed discrete electron dense bodies that later fused with cyto-plasmic granules to form phagolysosomes. Ultra structural results demonstrate that colloidal carbon is actively phagocytized by cytoplasmic granules (lysosomes) in the spleen ofO. niloticus. Direct phagocytic reaction of cells in the presence of an antigen is therefore very important in immunity.

Key words: Tilapia, Oreochromis niloticus, ultrastructure, colloidal carbon, phagocytic activities.