In the current study we used transthoracic echocardiography to measure stroke volume (SV), heart rate (fH), and cardiac output (CO) in adult bottlenose dolphins (Tursiops truncatus), a male beluga calf (Delphinapterus leucas, body mass [Mb] range: 151-175 kg), and an adult female false killer whale (Pseudorca crassidens, estimated Mb: 500-550 kg) housed in managed care. We also recorded continuous electrocardiogram (ECG) in the beluga, bottlenose dolphin, false killer whale, killer whale (Orcinus orca), and pilot whale (Globicephala macrorhynchus) to evaluate cardiorespiratory coupling while breathing spontaneously under voluntary control. The results show that cetaceans have a strong Respiratory Sinus Arrythmia (RSA), during which both fH and SV vary within the interbreath interval, making average values dependent on the breathing frequency (fR). The RSA-corrected fH was lower for all cetaceans compared to similarly sized terrestrial mammals breathing continuously. As compared with terrestrial mammals, the RSA-corrected SV and CO were either lower or the same for the dolphin and false killer whale, while both were elevated in the beluga. When plotting fR against fH for an inactive mammal, cetaceans had a greater cardiac response to changes in fR as compared with terrestrial mammals. We propose that these data indicate an important coupling between respiration and cardiac function that enhances gas exchange, and that this RSA is important to maximize gas exchange during surface intervals, similar to that reported in the elephant seal.
ABSTRACT We explored how humans adjust the stance phase mechanical function of their major lower-limb joints (hip, knee, ankle) during maximum acceleration sprinting. Experimental data [motion capture and ground reaction force (GRF)] were recorded from eight participants as they performed overground sprinting trials. Six alternative starting locations were used to obtain a dataset that incorporated the majority of the acceleration phase. Experimental data were combined with an inverse-dynamics-b...
ABSTRACT Pronounced dive responses through peripheral vasoconstriction and bradycardia enable 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 sound-and-movement tag (DTAG-3), we investigated the initiation and progression of bradyc...
The dive response is well documented for marine mammals, and includes a significant reduction in heart rate (fH) 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 fH while breathing. Using transthoracic echocardiography we measured fH, and stroke volume (SV) during voluntary surface apneas at rest up to 255 s, and during recovery from apnea in 11 adult bottlenose dolp...
ABSTRACT We measured respiratory flow ( V ), breathing frequency ( f R ), tidal volume ( V T ), breath duration and end-expired O 2 content in bottlenose dolphins ( Tursiops truncatus ) before and after static surface breath-holds ranging from 34 to 292 s. There was considerable variation in the end-expired O 2 , V T and f R following a breath-hold. The analysis suggests that the dolphins attempt to minimize recovery following a dive by altering V T and f R to rapidly replenish the O 2 stores. F...
Man-made environmental change may have significant impact on apex predators, like marine mammals. Thus, it is important to assess the physiological boundaries for survival in these species, and assess how climate change may affect foraging efficiency and the limits for survival. In the current study, we investigated whether the respiratory sinus arrhythmia (RSA) could estimate tidal volume (VT) in resting bottlenose dolphins. For this purpose, we measured respiratory flow and electrocardiogram (...
Abstract Heart rate (FH) accelerates in inspiration and decelerates in expiration, a phenomenon known as Respiratory Sinus Arrhythmia (RSA). Although the presence of RSA has been documented in many species, how its magnitude compares among species is unknown. We asked whether the magnitude of RSA in a large mammal, the horse, differed from that of previously measured humans. From electrocardiogram and pneumography, the peaks and troughs of FH were identified breath-by-breath in four horses (Ital...
Last. Frants H. Jensen(St And: University of St Andrews)H-Index: 17
view all 5 authors...
Toothed whales depend on sound for communication and foraging, making them potentially vulnerable to acoustic masking from increasing anthropogenic noise. Masking effects may be ameliorated by higher amplitudes or rates of calling, but such acoustic compensation mechanisms may incur energetic costs if sound production is expensive. The costs of whistling in bottlenose dolphins (Tursiopstruncatus) have been reported to be much higher (20–50% of resting metabolic rate, RMR) than theoretical predic...
Body composition (BC) is an emerging important factor for the characterization of metabolic status. The assessment of BC has been studied in various populations and diseases such as obesity, diabetes, endocrine diseases as well as physiological and paraphysiological conditions such as growth and aging processes, and physical training. A gold standard technique for the assessment of human BC at molecular level is represented by dual-energy X-ray absorptiometry (DXA), which is able to precisely as...
Bottlenose dolphins are highly versatile breath-holding predators that have adapted to a wide range of foraging niches from rivers and coastal ecosystems to deep-water oceanic habitats. Considerable research has been done to understand how dolphins manage O2 during diving, but little information exists on other gases or how pressure affects gas exchange. Here we used a dynamic multi-compartment gas exchange model to estimate blood and tissue O2, CO2 and N2 from high-resolution dive records of tw...
Heart rate monitoring in free-ranging cetaceans to understand their behavioural ecology and diving physiology is challenging. Here, we developed a simple, non-invasive method to monitor the heart rate of cetaceans in the field using an electrocardiogram-measuring device and a single suction cup equipped with an electrode. The unipolar suction cup was placed on the left lateral body surface behind the pectoral fin of Risso's dolphins (Grampus griseus) and a false killer whale (Pseudorca crassiden...
Plasticity in the cardiac function of a marine mammal facilitates rapid adjustments to the contrasting metabolic demands of breathing at the surface and diving during an extended apnea. By matching...
Ischemic events, such as ischemic heart disease and ischemic stroke, are the number one cause of death globally. Ischemia prevents blood, carrying essential nutrients and oxygen, from reaching the tissues leading to cell death, tissue death, and eventual organ failure. While humans are relatively intolerant to these ischemic events, other species, such as marine mammals, have evolved remarkable tolerance to chronic ischemia/reperfusion during diving. Here we capitalized on the unique adaptations...
Previous reports suggested the existence of direct somatic motor control over heart rate (f H) responses during diving in some marine mammals, as the result of a cognitive and/or learning process rather than being a reflexive response. This would be beneficial for O2 storage management, but would also allow ventilation-perfusion matching for selective gas exchange, where O2 and CO2 can be exchanged with minimal exchange of N2. Such a mechanism explains how air breathing marine vertebrates avoid ...
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 respirato...
