Re-evaluating the significance of the dive response during voluntary surface apneas in the bottlenose dolphin, Tursiops truncatus

• Published in: Scientific reports 2019-06, Vol.9 (1), p.8613-10, Article 8613
• Main Authors: Fahlman, A., Miedler, S., Rocho-Levine, J., Jabois, A., Arenarez, J., Marti-Bonmati, L., García-Párraga, D., Cauture, F.
• Format: Article
• Language: English
• Subjects: 59; 631/443/1338/2729; 631/601/1737; 64; Animals; Apnea; Apnea - physiopathology; Aquatic mammals; Arrhythmia; Body mass; Bottle-Nosed Dolphin - physiology; Breath Holding; Cardiac Output - physiology; Cetacea; Diving; Diving - physiology; Dolphins & porpoises; Echocardiography; Female; Heart rate; Heart Rate - physiology; Humanities and Social Sciences; Least-Squares Analysis; Male; Marine mammals; multidisciplinary; Regression Analysis; Respiration; Rest - physiology; Science; Science (multidisciplinary); Stroke Volume - physiology; Tachycardia; Tursiops truncatus
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-019-45064-8

The dive response is well documented for marine mammals, and includes a significant reduction in heart rate ( f H ) during submersion as compared while breathing at the surface. In the current study we assessed the influence of the Respiratory Sinus Arrhythmia (RSA) while estimating the resting f H while breathing. Using transthoracic echocardiography we measured f H , and stroke volume (SV) during voluntary surface apneas at rest up to 255 s, and during recovery from apnea in 11 adult bottlenose dolphins ( Tursiops truncatus , 9 males and 2 females, body mass range: 140–235 kg). The dolphins exhibited a significant post-respiratory tachycardia and increased SV. Therefore, only data after this RSA had stabilized were used for analysis and comparison. The average (±s.d.) f H , SV, and cardiac output (CO) after spontaneous breaths while resting at the surface were 44 ± 6 beats min −1 , 179 ± 31 ml, and 7909 ± 1814 l min −1 , respectively. During the apnea the f H , SV, and CO decreased proportionally with the breath-hold duration, and after 255 s they, respectively, had decreased by an average of 18%, 1–21%, and 12–37%. During recovery, the f H , SV, and CO rapidly increased by as much as 117%, 34%, and 190%, respectively. Next, f H , SV and CO rapidly decreased to resting values between 90–110 s following the surface apnea. These data highlight the necessity to define how the resting f H is estimated at the surface, and separating it from the RSA associated with each breath to evaluate the significance of cardiorespiratory matching during diving.