Cases of a Spontaneous Increase in Methemoglobin Concentration in Fish Blood during the Annual Cycle

Abstract—The dynamics of the content of erythrocyte number and concentration of methemoglobin in the blood of the thermophilic mullet (Chelon auratus Risso, 1810) and the cold-loving flounder (Platichthys flesus L., 1758) during the annual cycle has been studied. The degree of maturity of the circulating erythrocyte mass is judged on the basis of construction of acid erythrograms. A pronounced negative relationship is found between the number of red blood cells and the concentration of methemoglobin in the blood of both types (r = –0.681; –0.778). It has been shown that the youngest generation of red blood cells appears in the peripheral bed of both species in the postspawning period (1.5–2.0 months), which reflects the active production of erythrocytes by hematopoietic tissue. The rest of the time, there is a gradual aging of the circulating erythrocyte mass. This leads to a decrease in the number of red blood cells in the blood and is accompanied by an increase in the concentration of methemoglobin. The latter, apparently, determines the production of erythropoietins in the kidneys and activates the processes of erythropoiesis in hematopoietic tissue (prespawning period).