Cellular composition of the black scorpionfish (Scorpaena porcus, L 1758) blood and head kidney under short-time acute exposure to hypoxia

In the present work, we studied the effect of short-term acute hypoxia on the cellular composition of the blood and the head kidney of the black scorpionfish. Dissolved oxygen concentration was decreased from 8.5-8.7 mg O₂ l^-1 (normoxia) to 3-5 mg O₂ l^-1 (relative normoxia), 1-3 mg O₂ l^-1 (moderate hypoxia), and 0-1 mg O₂ l^-1 (acute hypoxia) within 1.5-2 h by bubbling of water with N₂. Exposure period was 4 h, water temperature was adjusted to 14-16 °C, and photoperiod was 12 h (light). Short-time acute hypoxia induced a rapid release of blast and immature cells from the head kidney into the circulating blood of the black scorpionfish, which was associated with reduction in erythropoietic reserves in 2.5 times. The number of immature erythroid cells (pronormoblasts, basophilic and polychromatophilic normoblasts) significantly increased in blood, and the simultaneously relative decrease of the number of abnormal red blood cell (RBC) and the increase of the number of RBC ghosts (lysed RBCs) in circulating blood were observed. The significant correlation between methemoglobin concentration and the number of RBC ghosts was shown (R² = 0.640 or r = 0.800). Hypoxia induced RBC swelling on 5-6% compared to control. The number of RBC ghosts in the blood is likely involved in the stimulation of erythropoietin production under hypoxia.