Respiratory sinus arrhythmia and submersion bradycardia in bottlenose dolphins (Tursiops truncatus).

Published on Jan 1, 2020in The Journal of Experimental Biology3.312
· DOI :10.1242/JEB.234096
Ashley M. Blawas4
Estimated H-index: 4
(Duke University),
Douglas P. Nowacek37
Estimated H-index: 37
(Duke University)
+ 2 AuthorsAndreas Fahlman30
Estimated H-index: 30
Sources
Abstract
Among the many factors that influence the cardiovascular adjustments of marine mammals is the act of respiration at the surface, which facilitates rapid gas exchange and tissue re-perfusion between dives. We measured heart rate (f H) in six, adult male bottlenose dolphins (Tursiops truncatus) spontaneously breathing at the surface to quantify the relationship between respiration and f H, and compared this to f H during submerged breath-holds. We found that dolphins exhibit a pronounced respiratory sinus arrhythmia (RSA) during surface breathing resulting in a rapid increase in f H after a breath followed by a gradual decrease over the following 15-20 seconds to a steady f H that is maintained until the following breath. RSA resulted in a maximum instantaneous f H (if H) of 87.4±13.6 beats min-1, a minimum if H of 56.8±14.8 beats min-1, and the degree of RSA was positively correlated with the inter-breath interval (IBI). The minimum if H during 2-minute, submerged breath-holds where dolphins exhibited submersion bradycardia (36.4±9.0 beats min-1) was lower than the minimum if H observed during an average IBI, however during IBIs longer than 30 seconds, the minimum if H (38.7±10.6 beats min-1) was not significantly different from that during 2-minute breath-holds. These results demonstrate that the f H patterns observed during submerged breath-holds are similar to those resulting from RSA during an extended IBI. Here we highlight the importance of RSA in influencing f H variability and emphasize the need to understand its relationship to submersion bradycardia.
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