Abstract
ABSTRACTThe objective of this study was to examine how the respiratory metabolism of the snakehead Channa argus changed when it shifted from breathing water to breathing air, and how increased metabolic demands caused by temperature, feeding, and exhaustive exercise affect its survival in air. The results demonstrated that the oxygen consumption rate (MO2) of the snakehead was lower for aerial respiration than aquatic respiration by 12.1, 24.5 and 20.4% at 20, 25, and 30°C, respectively. Survival time was significantly shortened with increasing temperature and was negatively correlated with the resting MO2 in air (MO2Air). No obvious feeding metabolic response was observed in the snakeheads fed at 1% and 3% body mass levels while breathing air. The maximum MO2Air of the snakehead after exhaustive exercise was significantly higher than the resting MO2Air of the control group. The results suggest that the snakehead could survive out of water by breathing air for varying lengths of time, depending on ambient temperature and metabolic demand. Additionally, some degree of metabolic depression occurs in the snakehead when breathing air. The metabolic demand associated with exercise in the snakehead, but not that associated with feeding, can be supported by its capacity for breathing air to some extent.
Highlights
The snakehead Channa argus is a species of bimodal breathing fish
The objective of this study was to examine how the MO2 of the snakehead changes when it shifts from breathing water to breathing air and how the increased metabolic demand caused by temperature, feeding and exhaustive exercise affects its survival in air
No obvious metabolic response was observed in the air-breathing snakeheads based on feeding behavior
Summary
The snakehead Channa argus is a species of bimodal breathing fish. It can breathe air at the water’s surface when water oxygen concentrations are reduced (Ishimatsu and Itazawa, 1981) through accessory air-breathing with a suprabranchial organ (Ishimatsu and Itazawa, 1981; Graham, 1997; Lefevre et al, 2014). It has been reported that approximately 60% of the routine metabolism of the snakehead can be attributed to breathing air at the surface (Itazawa and Ishimatsu, 1981). This species is widely distributed in China. The authors were interested in exploring how aerial respiration contributes to the survival of the snakehead in air
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