Circulation in the cephalopod, Octopus Dofleini

Abstract

1. 1. Simultaneous recordings of pressure from the cephalic aorta, the afferent and efferent branchial vessels and the vena cava cephalica have been made in unanethetized, unreastrained cephalopods, Octopus dofleini. 2. 2. The frequency of the systemic heart varied between 8–18 beats/min at a water temperature of 7–9°C. The aortic systolic pressure varied during normal conditions between 45–70 cm of water with a pulse pressure of 20 cm of water. The pressure level in the afferent branchial vessels ranged from 25 to 50 cm of water systolic and about 15 cm of water diastolic pressure. Similar values in the efferent branchial vessels were 10–25 cm of water systolic and 5–15 cm of water diastolic. In the vena cava cephalic the pressure ranged under normal conditions between 0–17 cm of water with a pulse pressure of 3–5 cm of water. 3. 3. The pressure recordings indicate that the ctenidia contract actively in a rhytmic fashion, promoting the propulsion of blood. The pressure changes in the vena cava cephalica are thought to be passively mediated from pressure changes created by the respiratory movements. 4. 4. During exercise there is a marked increased in both pulse pressure and diastolic pressure in the aorta. The heart sometimes showed great acceleration during exercise. 5. 5. Experiments with infusion of sea water into the vascular system demonstrated a capacity for accomodation of large volumes without noteceable disturbance of the general circulation. 6. 6. Pressure recordings in a symmetrical arrangement in the branchial vessel indicate a crucial importance of the nervous system for coordination of activity in the octopus vascular system. 7. 7. The haemodynamics of the cardiovascular system in Octopus dofleini are discussed.