Forced and voluntary diving in ducks: cardiovascular adjustments and their control

Abstract

1988. Forced and voluntary diving in ducks: cardiovascular adjustments and their control. Can. J . Zool . 66: 75 -83. Diving ducks submerge voluntarily for less than 1 min yet, in forced dives in the laboratory, redhead ducks can endure at least 8 min underwater. This is much longer than a dabbling duck of the same body mass can endure and is a result of the quicker onset of oxygen-conserving cardiovascular responses in divers. Oxygen conservation during forced dives is indicated by a profound bradycardia as blood flow is restricted to cerebral and central cardiovascular areas. In voluntary dives, on the other hand, heart rate is frequently above resting rates, and blood flow is preferentially directed to the working muscles of the hind limbs. Profound bradycardia only occurs in unrestrained ducks when they are trapped underwater. Since leg movements cease within 30 s after ducks are trapped, blood flow must at that time be directed away from the working muscles, as in the "classical" oxygen-conserving dive response. Cardiovascular adjustments to forced diving are caused by stimulation of nasal receptors in diving ducks. In dabblers, arterial chemoreceptor stimulation is crucial to the response, although an intact barostatic system may be necessary for development of profound bradycardia. Baroreceptors are essential for the cardiac response observed when dabblers are trained to dive for food, although neither baro-, chemo-, nor naso-receptors appear to have much to do with the cardiac adjustments to voluntary submergence in diving ducks. Nevertheless, in divers, cardiac adjustments to dabbling and forced, voluntary, and trapped dives are linearly related on a plot of dive (trapped) against the logarithm of predive (pretrap) heart rate. This relationship is due to a similar increase in vagal activity, of some 50% of maximum, in all types of diving manoeuvers. Phychogenic factors, long thought to be important in cardiac responses to forced diving, would appear to underpin this relationship. JONES, D. R., FURILLA, R. A., HEIEIS, M. R. A., GABBOTT, G. R. J., et SMITH, F. M. 1988. Forced and voluntary diving in ducks: cardiovascular adjustments and their control. Can. J. Zool. 66 : 75 -83. Les plongCes volontaires des canards plongeurs ne durent pas plus de 1 min et pourtant, en laboratoire, Aythya americana peut supporter des plongCes forcCes d'au moins 8 min.Ces durCes sont beaucoup plus longues que chez les canards de surface de meme masse, grice a la mise en place plus rapide des mCcanismes cardiovasculaires conservateurs d'oxygkne. La conservation d'oxygkne se manifeste par une profonde bradycardie, alors que le debit sanguin est circonscrit dans les rCgions cCrCbrales et cardiovasculaires centrales. Au cours des plongCes volontaires, au contraire, la frkquence cardiaque est souvent supkrieure la frkquence de repos et le debit sanguin est orient6 de fagon prkfCrentielle vers les muscles actifs des pattes. Chez les canards plongeurs libres, la bradycardie profonde ne se produit que s'ils sont piCgCs sous l'eau. Co...

Heart rate regulation and extreme bradycardia in diving emperor penguins

“…This distribution emphasizes that extremely low values are only present in longer dives, with the degree of bradycardia reflecting dive duration. Such extremely low values of f H have been demonstrated in free diving seals (Andrews et al, 1997;Thompson and Fedak, 1993), but in birds, have only been documented in forced submersion or exclusion studies (Butler, 1982;Butler and Jones, 1968;Folkow et al, 1967;Jones, 1969;Jones et al, 1988;Jones and Holeton, 1972;Ponganis and Kooyman, 2000;Stephenson et al, 1986). Low f H , present in later portions of long dives, may reflect a reinforcement of the initial bradycardia by low O 2 partial pressure (P O 2), through a possible chemoreceptor response (Butler and Stephenson, 1988;Enstipp et al, 2001).…”

How do cormorants counter buoyancy during submerged swimming?

“…Air-breathing divers are limited not only by a limited oxygen supply, and by pressure changes with depth (Boyd, 1997;Butler, 2001;Jones et al, 1988), but also by the need to carry air volumes underwater. These air volumes increase buoyancy by reducing the overall body density, hence the diver has to face a hydrostatic force acting to push it toward the surface (Alexander, 1968;Fish et al, 2002;Stephenson, 1993;Taylor, 1994;Webb et al, 1998).…”

Emergencies and Critical Care of Commonly Kept Fowl

“…The apnea and bradycardia that occur when an induction mask is placed over the beak and face are consequences of a stress response caused by stimulation of trigeminal nerve receptors. [40][41][42] Preoxygenation with 100% oxygen for several minutes reduced this response in dabbling but not diving ducks. 41 The isoflurane vaporizer is set to 3% to 4% for induction.…”

“…[40][41][42] Preoxygenation with 100% oxygen for several minutes reduced this response in dabbling but not diving ducks. 41 The isoflurane vaporizer is set to 3% to 4% for induction. 6 Intubation with a noncuffed endotracheal tube is recommended for anesthetic procedures lasting more than 15 minutes.…”