... anthropogenic disturbances, such as exposure to sonar. When exposed to sonar, beaked whales extend dive duration and increase swim speed as they rapidly evade the sound source ( DeRuiter et al., 2013 ). Increased swim speed could reduce the level of diving bradycardia, as shown in bottlenose dolphins ( Noren...

...Siri L. Elmegaard; Birgitte I. McDonald; Peter T. Madsen 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...

... of these factors on diving heart rate are poorly understood because of the difficulty of parsing their relative contributions in diving pinnipeds. Here, we examined the effects of apnea and external sensory inputs as autonomic drivers of bradycardia. Specifically, we hypothesized that (1) water stimulation...

..., in which the most active muscles, which would otherwise consume a significant amount of the blood oxygen, are shut off from circulation and use the local oxy-myoglobin for aerobic metabolism, without compromising the blood oxygen store. However, this cannot be done without a certain degree of bradycardia...

... of bradycardia would be influenced by dive duration and activity, i.e. the dive f H response would be exercise modulated. In all dives, f H decreased compared with surface rates by at least 50% (mean maximum surface f H =173 beats min −1 , mean minimum dive f H =50 beats min −1 ); however, dive f H...

... depression at elevated temperatures. Here, we investigated how water temperature (both acute and chronic exposures) affected the physiology of juvenile estuarine crocodiles ( Crocodylus porosus ) performing predator avoidance dives (i.e. fright-dives). Diving oxygen consumption, ‘fright’ bradycardia...

...–contraction coupling genes were studied in fish acclimatised to normoxia in summer (+18°C) or winter (+2°C), and in winter fish after 1, 3 and 6 weeks of anoxia. Anoxia induced a sustained bradycardia from a heart rate of 10.3±0.77 beats min −1 to 4.1±0.29 beats min −1 ( P <0.05) after 5 weeks, and heart...

...% in reference fish) and reduced intrinsic cardiac pacemaker rate. A barostatic response was evident in both groups, as pharmacologically induced increases and decreases in blood pressure resulted in atropine-sensitive bradycardia and tachycardia, respectively. Yet, the tachycardia in Biotest fish...

...Shawn R. Noren; Traci Kendall; Veronica Cuccurullo; Terrie M. Williams SUMMARY A hallmark of the dive response, bradycardia, promotes the conservation of onboard oxygen stores and enables marine mammals to submerge for prolonged periods. A paradox exists when marine mammals are foraging underwater...

... mediated response and not due to humoral factors released by myocardial or vascular stretch, for instance. The bradycardia during dorsal aortic occlusion typically lasted throughout the entire episode of occlusion,indicating that the response was not a startle response, and as such would have been expected...

... ). Atropine was able to inhibit the branchial vascular responses to ACh but not the hypoxic bradycardia, suggesting the presence of muscarinic receptors on the heart and gill vasculature, and that the hypoxia induced bradycardia is of non-cholinergic origin. The results suggest that adenosine mediates...

... bradycardia sleep ontogeny cardiorespiratory control harbour seal Phoca vitulina The obligation to surface periodically and replenish oxygen stores limits the underwater foraging capacity of marine mammals. To compensate for this need, most marine mammals possess a suite of physiological...

.... Injection (0.1-0.3 mm deep) in different rostrocaudal, medial-lateral positions induced a bradycardia, either increased or decreased blood pressure, ventilation frequency and amplitude and, sometimes, an initial apnea. Often these responses occurred simultaneously in various different combinations...

...Nicole M. Elliott; Russel D. Andrews; David R. Jones SUMMARY While diving, harbour seals ( Phoca vitulina ) manage their oxygen stores through cardiovascular adjustments, including bradycardia, a concurrent reduction in cardiac output, and peripheral vasoconstriction. At the surface,post-dive...

.... This was accomplished by measuring cardiorespiratory variables during acute hypercarbia (20 min at P CO 2 =8 mmHg; 1 mmHg=0.133 kPa) in fish subjected to selective bilateral extirpation of the first gill arch. The cardiovascular responses to hypercarbia in the intact fish included a significant bradycardia (from 75.0...