Hemopoiesis, lymphomyeloid tissues, spleen and thymus of torpedoes: in normal conditions and after treatment with cobamamide and folic acid.

Following our previous works on the morphology (Pica et al., 1983) and cytochemistry (Grimaldi et al., 1983) of the blood cells of Torpedoes, hereunder are reported the results of the observations on histological sections and imprints of lymphomieloid tissues, spleen and thymus before and after injections with cobalamide and folic acid. Erythropoiesis, lymphocytopoiesis, thrombocytopoiesis and, very likely, monocytopoiesis take place in the spleen. Erythroid cells are: proerythroblasts, basophilic erythroblasts I and II, acidophilic erythroblasts and mature erythrocytes. Lymphocytopoiesis evolves from lymphoblast to promielocyte and mature small lymphocyte. Thrombocytopoiesis starts from prothrombocytes and evolves first into round thrombocytes and then into spindle shaped ones. Monocytopoiesis occurs in lymphomieloid tissue (oesophageal and epigonal) through maturative stages similar to theose of mammals: mieloblasts, promielocytes and mielocytes both neutrophilic and eosinophilic. In the animals caught in autumn which show a slowed hemopoiesis, the treatment with injections of cobamamide and folic acid produces an increase of mithotic index both in red and white cells and their maturation speedrate rises to the same level as the maximum of summer season. Thymus consists of lobes and lobules which contain a cortex and a medulla as in man. The cell types here present: epithelial-reticular cells which grow and fill of acidophilic granules, large adypocytes and Hassal's corpuscles. Lymphocytopoiesis does not presumably take place here.