Granulopoiesis in the head kidney of Sparus auratus.

The head kidney of Sparus auratus (teleost) is comprised of erythropoietic, granulopoietic and lymphopoietic cells. This study describes the ultrastructure of the granulopoietic series of cells. Heterophils, eosinophils and basophils were found at various stages of development. The most numerous cells are the neutrophils, the cells of the basophilic series being very scarce. The most outstanding characteristics of the neutrophil series are the eccentric and slightly segmented nucleus and cytoplasm with numerous, homogeneously dense granules. The eosinophils show a lobed nucleus and two types of granules in the cytoplasm. In the basophils, the cytoplasmic granules are large with fibrillar contents.