Dear colleagues, We are happy to announce the publication of a study investigating the physical stimulators of diving bradycardia and surfacing tachycardia in trained harbour porpoises, providing insight into the drivers of the cetacean diving physiology. We found that blowhole submergence is an important driver of bradycardia, while apnoea will lead to delayed bradycardia; however, anticipatory/volitional modulation can overrule such responses to sensory inputs. Drivers of the dive response in trained harbour porpoises (Phocoena phocoena) Siri L. Elmegaard, Birgitte I. McDonald and 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 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 bradycardia and tachycardia during apnoea and eupnoea for varying levels of immersion. We show that paranasal wetting drives bradycardia initiation and progression, whereas apnoea leads to dive-level bradycardia eventually, but not instantly. At the end of dives, heart rate accelerates independently of lung expansion, perhaps in anticipation of surfacing; however, full tachycardia is only engaged upon inhalation. We conclude that breathing drives surface tachycardia, whereas blowhole wetting is an important driver of bradycardia; however, anticipatory/volitional modulation can overrule such responses to sensory inputs. Find the paper via Journal of Experimental Biology: http://jeb.biologists.org/lookup/doi/10.1242/jeb.208637 Or I will be happy to share a copy upon request. Best wishes, Siri Siri Lander Elmegaard PhD fellow, Dept. Bioscience Section for Zoophysiology & Section for Marine Mammal Research Aarhus University, Denmark (+45) 26858014 siri@bios.au.dk<mailto:siri@bios.au.dk> [AU-logo-mail-150]
