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diving crocodiles

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  • Marc Verhaegen
    Michael Axelsson & CE Franklin 2011 Compar Biochem & Physiol A160:1-8 Elucidating the responses and role of the cardiovascular system in crocodilians during
    Message 1 of 1 , Jul 1, 2011
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      Michael Axelsson & CE Franklin 2011 Compar Biochem & Physiol A160:1-8
      Elucidating the responses and role of the cardiovascular system in
      crocodilians during diving:
      fifty years on from the work of C.G. Wilber

      In 1960, Wilber in a laboratory-based study described for the first time the
      changes in heart rate with submergence in the American alligator, esp.the
      marked bradycardia that occurred during forced dives.
      This short review summarizes the major advances in our understanding of
      diving, and the responses and role of the cardio-vascular system, of
      crocodilians during submergence in the 50 yrs since Wilber published his
      findings.
      These advances are attributable in part to the technological advances made
      in physiological monitoring devices & wildlife telemetry, that have not only
      provided greater elucidation of the hemo-dynamics of the unique crocodilian
      cardio-vascular system, but also allowed the natural diving behaviors &
      heart rates in free-ranging crocodiles to be recorded.
      Of note, telemetric field-based studies have revealed that wild free-ranging
      crocodiles typically undertake only short dives, <20 min, yet crocodiles are
      also capable of dives of many hours in duration.
      In contrast to Wilber's study, dives recorded from free-ranging crocodiles
      were found to be accompanied by only a modest bradycardia, highlighting the
      often confounding effects associated with captive animals monitored under
      laboratory conditions.
      More recent studies have also documented the complex central flow & pressure
      patterns of crocodilians, including a pulmonary to systemic shunt that can
      be initiated by a unique intra-cardiac valve located in the subpulmonary
      conus.
      The role & significance of this cardiac shunt remains controversial, and the
      focus of recent lab-based studies.
      We contend that elucidation of the role & significance of the cardiac shunt
      in crocodilians will only be achieved by monitoring telemetrically the
      central cardio-vascular flows & pressures in non-captive animals that are
      undisturbed & free-ranging Š




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