Comparative Characterization of the Cellular Composition of the Black Scorpionfish (Scorpaena porcus L.) Hematopoietic Organs during the Spawning Season and the Period of Reproductive Inactivity

Abstract

Hematopoiesis in teleosts has a number of characteristics that are not fully understood. In the present work, the cellular composition of the hematopoietic organs (head kidney and spleen) of the black scorpionfish during the spawning season and the period of reproductive inactivity was studied using light microscopy. The morphology and the percentage of blood cells were described. The head kidney was shown to be the main hematopoietic organ of the black scorpionfish: immature blood cells of all hematopoietic lines at the different stages of differentiation were observed there. They were divided into 3 clusters depending on the average cell diameter. Lymphocytes, thrombocytes and colony-forming cells, the precursors for all types of blood cells, were observed within the cluster of small cells. The intermediate-size cluster comprised blast forms (erythroblasts and blasts of white blood cells). The large-size cluster consisted of maturing granulocytes, monocytes, macrophages, plasma cells, and mature erythrocytes. The spleen mainly contained mature erythrocytes, showing signs of senescence, and erythrocyte ghosts. Therefore, it was concluded that the spleen of the black scorpionfish performs the function of depositing and utilizing erythrocytes. The study also demonstrated the seasonal dynamics of hematopoiesis. The increase in the number of erythroblasts was recorded in the head kidney of spawning individuals. Erythroblasts were also found in the spleen, in spite of their total absence in the reproductively inactive fish. Consequently, the spleen of the black scorpionfish is an organ of secondary erythropoiesis, which functions when the hematopoietic capacity of the kidneys is insufficient