Ultrastructure of the renal granulopoietic tissue of the Rana ridibunda tadpole.

The ultrastructure of the renal hemopoietic tissue of Rana ridibunda tadpole has been studied. The main cell types of granulopoietic series are described. No erythropoiesis was found. The heterophilic series contained a first granular type, similar to those described in teleosts and other lower vertebrates but without crystalloid and a second with similar features to 'azurophilic' granules, described in other vertebrates. Specific granules found in mammalians were not observed. The origin and development of the granules have been discussed. Similarly, the eosinophilic series contained two granule types. Mature eosinophilic leukocytes were, at all times, seen in the sinusoidal lumen, a crystalloid core could be either present or absent in the granules. Basophilic leukocytes were extremely scarce, the granule content being homogeneous or crystalline.