skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Drivers of the dive response in trained harbour porpoises (Phocoena phocoena )
Pronounced dive responses through peripheral vasoconstriction and bradycardia enables prolonged apnoea in marine mammals. For most vertebrates, the dive response is initiated upon face immersion, but little is known about the physical drivers of diving and surfacing heart rate in cetaceans whose faces are always mostly submerged. Using two trained harbour porpoises instrumented with an ECG-measuring DTAG-3, we investigate the initiation and progression of bradycardia and tachycardia during apnoea and eupnoea for varying levels of immersion. We show that paranasal wetting drives bradycardia initiation and progression, whereas apnoea leads to dive-level bradycardia eventually, but not instantly. At the end of dives, heart rate accelerates independently of lung expansion, perhaps in anticipation of surfacing; however, full tachycardia is only engaged upon inhalation. We conclude that breathing drives surface tachycardia, whereas blowhole wetting is an important driver of bradycardia; although, anticipatory/volitional modulation can overrule such responses to sensory inputs.  more » « less
Award ID(s):
1159123
PAR ID:
10278958
Author(s) / Creator(s):
; ;
Date Published:
Journal Name:
Journal of Experimental Biology
Volume:
222
Issue:
19
ISSN:
0022-0949
Page Range / eLocation ID:
jeb208637
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; (, Journal of Experimental Biology)
    null (Ed.)
    The dive response, a decrease in heart rate (ƒH) and peripheral vasoconstriction, is the key mechanism allowing breath-hold divers to perform long duration dives. This pronounced cardiovascular response to diving has been investigated intensely in pinnipeds, but comparatively little is known for cetaceans, in particular in ecologically relevant settings. Here we studied the dive ƒH response in one the smallest cetaceans, the harbour porpoise (Phocoena phocoena). We used a novel multi-sensor data logger to record dive behaviour, ƒH, ventilations and feeding events in three trained porpoises, providing the first evaluation of cetacean ƒH regulation while performing a variety of natural behaviours, including prey capture. We predicted that tagged harbour porpoises would exhibit a decrease in ƒH in all dives, but the degree of bradycardia would be influenced by dive duration and activity, i.e., the dive ƒH response will be exercise modulated. In all dives, ƒH decreased compared to surface rates by at least 50% (mean maximum surface=173 beats min−1, mean minimum dive=50 beats min−1); however, dive ƒH was approximately 10 beats min−1 higher in active dives due to a slower decrease in ƒH and more variable ƒH during pursuit of prey. We show that porpoises exhibit the typical breath-hold diver bradycardia during aerobic dives and that the heart rate response is modulated by exercise and dive duration; however, other variables such as expectations and individual differences are equally important in determining diving heart rate. 
    more » « less
  2. ; ; ; (, American Journal of Physiology-Regulatory, Integrative and Comparative Physiology)
    Most animals elevate cardiac output during exercise through a rise in heart rate ( f H ), whereas stroke volume (V S ) remains relatively unchanged. Cardiac pacing reveals that elevating f H alone does not alter cardiac output, which is instead largely regulated by the peripheral vasculature. In terms of myocardial oxygen demand, an increase in f H is more costly than that which would incur if V S instead were to increase. We hypothesized that f H must increase because any substantial rise in V S would be constrained by the pericardium. To investigate this hypothesis, we explored the effects of pharmacologically induced bradycardia, with ivabradine treatment, on V S at rest and during exercise in the common snapping turtle ( Chelydra serpentina) with intact or opened pericardium. We first showed that, in isolated myocardial preparations, ivabradine exerted a pronounced positive inotropic effect on atrial tissue but only minor effects on ventricle. Ivabradine reduced f H in vivo, such that exercise tachycardia was attenuated. Pulmonary and systemic V S rose in response to ivabradine. The rise in pulmonary V S largely compensated for the bradycardia at rest, leaving total pulmonary flow unchanged by ivabradine, although ivabradine reduced pulmonary blood flow during swimming (exercise × ivabradine interaction, P < 0.05). Although systemic V S increased, systemic blood flow was reduced by ivabradine both at rest and during exercise, despite ivabradine’s potential to increase cardiac contractility. Opening the pericardium had no effect on f H , V S , or blood flows before or after ivabradine, indicating that the pericardium does not constrain VS in turtles, even during pharmacologically induced bradycardia. 
    more » « less
  3. ; ; ; (, Biology Open)
    null (Ed.)
    ABSTRACT Anthropogenic noise can alter marine mammal behaviour and physiology, but little is known about cetacean cardiovascular responses to exposures, despite evidence that acoustic stressors, such as naval sonars, may lead to decompression sickness. Here, we measured heart rate and movements of two trained harbour porpoises during controlled exposure to 6–9 kHz sonar-like sweeps and 40 kHz peak-frequency noise pulses, designed to evoke acoustic startle responses. The porpoises initially responded to the sonar sweep with intensified bradycardia despite unaltered behaviour/movement, but habituated rapidly to the stimuli. In contrast, 40 kHz noise pulses consistently evoked rapid muscle flinches (indicative of startles), but no behavioural or heart rate changes. We conclude that the autonomous startle response appears decoupled from, or overridden by, cardiac regulation in diving porpoises, whereas certain novel stimuli may motivate oxygen-conserving cardiovascular measures. Such responses to sound exposure may contribute to gas mismanagement for deeper-diving cetaceans. 
    more » « less
  4. ; ; ; ; (, Journal of Experimental Biology)
    null (Ed.)
    The dive response, bradycardia (decreased heart rate) and peripheral vasoconstriction, is the key mechanism allowing breath-hold divers to perform long-duration dives while actively swimming and hunting prey. This response is variable and modulated by factors such as dive duration, depth, exercise and cognitive control. This study assesses the potential role of exercise and relative lung volume in the regulation of heart rate (fH) during dives of adult female California sea lions instrumented with ECG, depth, and 3-axis acceleration data loggers. A positive relationship between activity (minimum specific acceleration) and fH throughout dives suggested increased muscle perfusion associated with exercise. However, apart from late ascent, fH during dives was still less than or equal to resting heart rate (on land). In addition, the activity-fH relationship was weaker in long, deep dives consistent with prioritization of blood oxygen conservation over blood oxygen delivery to muscle in those dives. Pulmonary stretch receptor reflexes may also contribute to fH regulation as fH profiles generally paralleled changes in relative lung volume, especially in shallower dives and during early descent and late ascent of deeper dives. Overall, these findings support the concept that both exercise and pulmonary stretch receptor reflexes may influence the dive response in sea lions. 
    more » « less
  5. (, Frontiers in Physiology)
    Physio-logging has the potential to explore the processes that underlie the dive behavior and ecology of marine mammals and seabirds, as well as evaluate their adaptability to environmental change and other stressors. Regulation of heart rate lies at the core of the physiological processes that determine dive capacity and performance. The bio-logging of heart rate in unrestrained animals diving at sea was infeasible, even unimaginable in the mid-1970s. To provide a historical perspective, I review my 40-year experience in the development of heart rate physio-loggers and the evolution of a digital electrocardiogram (ECG) recorder that is still in use today. I highlight documentation of the ECG and the interpretation of heart rate profiles in the largest of avian and mammalian divers, the emperor penguin and blue whale. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email