Ultrastructure of the peripheral blood leucocytes of Oreochromis mossambicus

Peripheral blood leucocytes were examined for their fine structure and their in vivo response to colloidal carbon particles and bacteria, Aeromonas salmonicida . Four main types of leucocyte were identified: lymphocytes, thrombocytes, monocytes and granulocytes. Previously, two types of granulocyte had been identified but at the electron microscope level a third type could be distinguished in the peripheral blood. Monocytes and the type 1 and type 3 granulocytes were found to be phagocytic.