Haemopoiesis in the head kidney of Sparus auratus.

The haemopoiesis of Sparus auratus is formed by the following series: erythro-thrombopoietic, granulopoietic, lymphoplasmapoietic and monocytes. All the cells which form these series originate from one cell called the stem-cell, there being a network of reticular cells and melanomacrophage centres amongst these cells. The erythropoietic series comprises erythroblast, proerythrocytes, polychromatocytes, reticulocytes and erythrocytes. The morphological changes which occur during the maturing process are: heterochromatinization of the nuclei, the gradual decrease of organelles in the cytoplasm and the increase of the haemoglobin. We also observed thrombocytes characterized by the presence of numerous vacuoles and abundant glycogen in the cytoplasm. In the lymphoplasmapoietic series are seen lymphoblasts, lymphocytes and plasma cells. The lymphocytes are cells of different sizes with small microvilli in the cell surface and scanty cytoplasm. Outstanding in the plasma cell is the well developed granular endoplasmic reticulum. The monocytes are large cells with an indented nucleus and cytoplasm containing numerous vesicles of different sizes and also a few lysosomes.