Aortic blood flow and cardiac output in the hemoglobin-free fish Chaenocephalus aceratus

Abstract

1. 1. The cardiac output of Chaenocephalus aceratus, determined by the Fick principle, ranged from 99 to 153 ml/kg per min in unrestrained specimens at rest. These values are several-fold higher than those of other fishes. 2. 2. The combined energy cost for cardiac and respiratory work at rest was estimated to be nearly half, or more, of the total oxygen consumption. 3. 3. The ventral aortic blood flow, measured by electromagnetic flowmeter, increased during hypoxia and decreased during hyperoxia. The cardiac output was regulated by changes in the stroke volume and not heart rate. 4. 4. The ventral and/or dorsal aortic blood pressures were monitored simultaneously with the blood flow. 5. 5. Infusions of cardio- and vasoactive drugs revealed typical responses.