Cardiorespiratory coupling in the bottlenose dolphin (Tursiops truncatus)

Area of Science:

• Marine Mammal Physiology
• Cardiorespiratory Physiology
• Comparative Physiology

Background:

• Bottlenose dolphins (Tursiops truncatus) are intermittent breathers with distinct exhalation and inhalation phases.
• Breathing significantly impacts heart rate (if _H) and stroke volume (iSV) in dolphins, causing transient tachycardia.
• Previous studies could not isolate the cardiac effects of exhalation versus inhalation due to short breath durations.

Purpose of the Study:

• To differentiate the specific effects of exhalation and inhalation on instantaneous heart rate (if _H) in bottlenose dolphins.
• To enhance understanding of cardiorespiratory coupling mechanisms in marine mammals.

Main Methods:

• Investigated three male bottlenose dolphins trained for isolated respiratory phase holds (expiration and inhalation).
• Measured instantaneous heart rate (if _H) responses during separated exhalation and inhalation.
• Analyzed the distinct contributions of each respiratory phase to cardiac function.

Main Results:

• Inhalation was associated with a significant increase in instantaneous heart rate (if _H).
• Expiration was correlated with a decrease in instantaneous heart rate (if _H).
• These findings demonstrate differential cardiac responses to distinct respiratory actions.

Conclusions:

• Both inhalation and exhalation exert specific, opposing influences on bottlenose dolphin heart rate.
• This study clarifies the cardiorespiratory coupling by distinguishing the roles of each respiratory phase.
• Provides novel insights into the physiological control of breathing and heart rate in cetaceans.