Heart rate in resting seals on land and in water

• Published in: Comparative biochemistry and physiology. A, Comparative physiology Vol. 67; no. 1; pp. 77 - 83
• Main Authors: Påsche, Arvid, Krog, John
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 1980
• ISSN: 0300-9629
• DOI: 10.1016/0300-9629(80)90410-7

1. 1. Heart rate of unrestrained resting seals was recorded under three different conditions: (a) on land, (b) in water, and (c) with only the head above the water. 2. 2. A comparison of the heart rates obtained showed that there was no significant difference in the bradycardia during diving and apneic periods on land. 3. 3. In both cases the heart rate decreased to 30% of the rate during breathing. Nor was a difference found in the time course of the bradycardia in water and on land. 4. 4. The observed bradycardia seemed to be correlated to a Valsalva-like maneuver, which is known to cause a change in intrathoracic pressure. 5. 5. Changes in the intrathoracic pressure, caused by muscular contraction, might occur during the dives. 6. 6. Such changes could then explain the variation in heart rate seen during some of the dives and apneic periods. 7. 7. A correspondence between ventilation and variation in heart rate was found, but only in the young seals while they had an unusually low ventilation rate.