The Dimensional and Physiological-Biochemical Parameters of Erythrocytes and Gill and Heart Indices in Some Benthic Fish of the Black Sea Coast of the Southeastern Crimea

The dimensional and physiological-biochemical parameters of erythrocytes, as well as the gill and heart indices, were studied in five species of marine benthic fish. The black scorpionfish Scorpaena porcus Linnaeus, 1758 and the shore rockling Gaidropsarus mediterraneus Linnaeus, 1758 differed from the other species in a larger mass of the heart and gill apparatus, which indicates more efficient transport capabilities of the circulatory system of these fish. The linear size characteristics of erythrocytes of a cartilaginous fish, the thornback ray Raja clavata Linnaeus, 1758, were 1.5–2 times higher than those of erythrocytes of S. porcus , which were the largest among the studied teleosts. The sizes of the erythrocytes of three other teleost species differed insignificantly. The amount of hemoglobin per unit surface area of erythrocyte, which reflects the efficiency of hemoglobin saturation with oxygen, insignificantly varied (0.05 to 0.071 pg/mm 2 ) among the studied bony fish. In contrast, in the thornback ray this parameter was 2.7–3.8 times lower. The intracellular glycogen concentration, which characterizes the degree to which the erythrocyte is independent of glycemic fluctuations, was highest in cells of S. porcus (305.2 ± 35.1 mg %), while it was lowest in erythrocytes of the thornback ray R. clavata (142.8 ± 15.1 mg %). The ecto-ATPase activity was higher in large erythrocytes of S. porcus , R. clavata , and Uranoscopus scaber (4.8, 3.1, and 1.6 μmol P in /min/mL of erythrocytes, respectively) than in smaller erythrocytes of Crenilabrus tinca and Gaidropsarus mediterraneus (0.5 and 0.4, μmol P in /min/mL of erythrocytes, respectively). This confirms the assumption that erythrocytes use the thermal energy from hydrolysis of extracellular ATP to “warm” their own membrane, which leads to the change in the rheological characteristics of blood in the capillary blood flow.