MEAGHER, E.*; PABST, D.A.; MCLELLAN, W.; WESTGATE, A.; WELLS, R.: Heart rate, respiration and heat flux across the dorsal fin in wild bottlenose dolphins, Tursiops truncatus
The dolphin dorsal fin is a thermal window, invested with blood vessels that function to conserve or dissipate body heat depending on thermoregulatory demands. Heat flux, measured at a single position on the dorsal fin of bottlenose dolphins, decreases during dives, relative to values measured at the surface (Williams et al., 1999). This decrease has been attributed to diminished peripheral blood flow as a result of bradycardia during a dive. Dolphins, however, are arrhythmic breathers, experiencing cycles of bradycardia, followed by an associated tachycardia during respiration, even while resting at the surface. Thus, we hypothesized that heat flux across the dorsal fin would decrease during apneustic periods at the surface. We took simultaneous and continuous recordings of heart rate, respiration and heat flux at three positions on the dorsal fin (in air and with fin submerged) of 19 wild bottlenose dolphins. Tachycardia was associated with each respiratory event and heart rate, although variable, decreased during intervening breathholds. Heat flow across the dorsal fin in air ranged from -60W/m2 (gaining heat) to 150 W/m2, while heat flow during submergence ranged from 25 W/m2 to 225 W/m2. Although no consistent pattern between heart rate and heat flux was evident, heat flow values depended strongly upon fin position. Heat flow measured at two sites on the center of the fin- one directly over a superficial vein and the other purposely avoiding a vein- could differ by as much as 125 W/m2. These results suggest heat flux across the dorsal fin is strongly influenced by underlying patterns of vasculature. Funded by NMFS.
