... 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...

...% 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...

...–58% of their f H,max while active at depth and approached 57–79% of their f H,max during anticipatory tachycardia as the animals glided to the surface. f H was significantly correlated with stroke frequency (range=0–2.5 strokes s −1 , r =0.88, N =25 dives) and calculated swim speed (range=0–5.4 m s...

... occlusion resulted in tachycardia(62.4±2.4 to 69.1±1.7 beats min –1 ), decreased venous capacitance reflected as an increase in MCFP (0.17±0.03 to 0.27±0.03 kPa) and increased P da (4.0±0.2 kPa compared to 3.2±0.1 kPa before occlusion). Post-branchial occlusion somewhat reversed the responses since f H...