Heartbeat frequencies and blood pressures were monitored in free-moving Octopus vulgaris. Typical resting frequencies (for animals of 500 g ± at 22° C) were 40-50 beats min−1, with resting pressures measured at the dorsal aorta of 40 cm H2O in systole and 15 cm in diastole, rising to 100 cm or more with a pulse of 50 cm in exercise. Beat frequency changes very little and any increased oxygen demand results mainly in an increase in stroke volume. Temperature affects heartbeat frequency with a Q10 of about 3 over the range 7–27 °C. Systemic heartbeat rate and pulse amplitude also change with the oxygen content of the water, slowing as this decreases and stopping, reversibly (at least for short periods), at about 2.5 parts O2 per million.

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