Extreme bradycardia and tachycardia in the world’s largest animal

摘要: The biology of the blue whale has long fascinated physiologists because animal's extreme size. Despite high energetic demands from a large body, low mass-specific metabolic rates are likely powered by heart rates. Diving bradycardia should slow blood oxygen depletion and enhance dive time available for foraging at depth. However, whales exhibit high-cost feeding mechanism, lunge feeding, whereby volumes prey-laden water intermittently engulfed filtered during dives. This paradox such large, slowly beating cost represents unique test our understanding cardiac function, hemodynamics, physiological limits to body Here, we used an electrocardiogram (ECG)-depth recorder tag measure dives as deep 184 m 16.5 min. Heart were typically 4 8 beats min-1 (bpm) 2 bpm, while after-dive surface 25 37 near estimated maximum rate possible. bradycardia, recorded 2.5-fold increase above diving minima ascent phase lunges followed gradual decrease prolonged glide is filtered. These dynamics explain hemodynamic design in rorqual consisting large-diameter, highly compliant, elastic aortic arch that allows aorta accommodate ejected maintain flow variable pauses between heartbeats.