How does the snakehead Channa argus survive in air? The combined roles of the suprabranchial chamber and physiological regulations during aerial respiration

This study aimed to test the hypothesis that the aerial survival of the northern snakehead is involved not only with suprabranchial chamber respiration but also with physiological regulations. The aerial survival time and oxygen consumption rate (VO2) were determined in snakeheads with either normal or injured suprabranchial organs. Some hematological and biochemical parameters were assessed during aerial exposure. The results showed that resting VO2 decreased when switching from water to air in both the control and the suprabranchial organ-injured fish, with decreases of 22.4% and 23.5%, respectively. Resting VO2 in air was not different between the control and the suprabranchial organ-injured fish. The red blood cell (RBC) count and hemoglobin concentration showed no marked changes, while RBC size increased when exposed to air. The liver lactate concentration remained unchanged, and the white muscle lactate concentration decreased when switching from water to air. The blood ammonia concentration tended to increase during aerial respiration. These results suggest that the aerial survival of the snakehead is positively associated with a combination of factors, including respiration of suprabranchial organs and other accessory organs, depressed metabolic demands and increased oxygen transport, and negatively associated with the accumulation of blood ammonia but not anaerobic metabolism.