Characteristics of erythron of the head kidney and circulating blood of the flounder gloss (<i>Platichthys flesus</i>) during the annual cycle

Abstract

The erythron composition of the head kidney (pronephros) and circulating blood in the cold-loving flounder-gloss (Platichthys flesus L., 1758) during the annual cycle was studied. The erythron of pronephros was mainly represented by erythroblasts (EB) and basophilic normoblasts (BN). The content of polychromatophilic normoblasts (PN) was low (less than 2%). The maximum size of the erythroid germ of hematopoiesis in the pronephros was noted during the post-spawning period (April–July). It accounted for up to 17% of the cellular mass of the prints. BN and PN, which were not capable of proliferation, mainly prevailed in the blood. The maximum content of these cell forms was also noted during the post-spawning periods. Cells of earlier generations (EB) were not detected at all in the blood. The increase in the production of erythroid cells by hematopoietic tissue coincided with an increase in the number of circulating erythrocytes in the blood of flounder-gloss (R2 0.608 and 0,991), which indicated a shift in the erythrocyte balance in the red blood system in favor of production processes. The factors responsible for the generation of erythrocytes by hematopoietic tissue in fish in a spawning state are considered.