Abstract
1. 1. Ventral aortic blood velocity and pressure in free-swimming elasmobranchs were recorded with the Doppler ultrasonic telemetry blood flowmeter. 2. 2. Ejection time from the heart varied with the heart rate. Peak injection velocities ranged from 12–14 cm/sec in Horn sharks, 12–20 cm/sec in skates and 8–15 cm/sec in dogfish. Acceleration of the blood lasted from 120 msec in the Horn shark (T = 24°C) to 450 msec in the skates (T = 9°C). Deceleration of flows was slow in all species. Oscillations from bulbus cordis contraction and respiratory movements were superimposed on the basic wavefrom. Participation of the bulbar contraction in the cardiac sequence varied widely. 3. 3. Heart rates increased during short-lasting exercise. Peak velocity and flow were largeley unchanged. Peak velocity and flow frequently increased in the post-exercise period. 4. 4. The hemodynamic effects of atropine, acetylcholine and adrenaline are discussed in relation to the fact that the fish heart receives parasympathetic but not, apparently, sympathetic innervation.
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