|
| |
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
First published online May 5, 2005
Journal of Experimental Biology 208, 1971-1991 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01583
Physiological control of diving behaviour in the Weddell seal Leptonychotes weddelli: a model based on cardiorespiratory control theory
Department of Zoology, University of Toronto, Toronto, Ontario, Canada M5S 3G5
e-mail: rstephsn{at}zoo.utoronto.ca
Accepted 10 March 2005
Despite being obligate air breathers, many species of marine mammal are capable of spending most of their lives submerged in water. How they do this has been a subject of intense interest to physiologists for over a century, yet we still do not have a detailed understanding of the physiological mechanisms underlying this behaviour. What are the proximate mechanisms that trigger the 'decisions' to submerge and return to the surface? The present study proposes a model intended to address this question, based on fundamental concepts of cardiorespiratory control. Two basic hypotheses are examined by computer simulation, using a mathematical model of the mammalian cardiorespiratory control system with parameter values for an adult Weddell seal: (1) that the control of diving can be considered to be a respiratory control problem, and (2) that dives are initiated and maintained by disfacilitation of respiratory drive, not inhibition. Computer simulations confirmed the plausibility of these hypotheses. Simulated diving behaviour and physiological responses (ventilation, cardiac output, blood and tissue gas tensions) were consistent with published data from freely diving Weddell seals. Dives up to the estimated aerobic dive limit (ADL, 18-25 min) could be simulated without the need for active inhibition of breathing in this model. This theoretical analysis suggests that the most important physiological adjustments occur during the surface interval phase of the dive cycle and include hyperventilation accompanied by high cardiac output, appropriate regulation of cerebral blood flow and central chemoreceptor threshold shifts. During dives, cardiac output, distribution of peripheral blood flow, splenic contraction and peripheral chemoreflex drives were found to modulate physiological and behavioural responses, but were not essential for simulated dives to occur. The main conclusion from this study is that the central chemoreceptor may be an important mechanism involved in the regulation of diving behaviour, implying that CO2, not O2, is the key regulatory variable in this model. This model includes and extends the ADL concept and suggests an explicit mechanism by which the respiratory control system may play a central role in the regulation of diving behaviour. It is likely that respiratory mechanisms are an important component of a hierarchical behavioural control system and further studies are required to test the qualitative and quantitative validity of the model.
Key words: diving, Weddell seal, cardiorespiratory control, model, behaviour
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati 
Twitter What's this?
This article has been cited by other articles:
|
|
 |
|
  P. J. Ponganis, U. Kreutzer, T. K. Stockard, P.-C. Lin, N. Sailasuta, T.-K. Tran, R. Hurd, and T. Jue Blood flow and metabolic regulation in seal muscle during apnea J. Exp. Biol., October 15, 2008; 211(20): 3323 - 3332. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. K. Stockard, D. H. Levenson, L. Berg, J. R. Fransioli, E. A. Baranov, and P. J. Ponganis Blood oxygen depletion during rest-associated apneas of northern elephant seals (Mirounga angustirostris) J. Exp. Biol., August 1, 2007; 210(15): 2607 - 2617. [Abstract] [Full Text] [PDF]
|
|
