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Journal of Comparative Physiology B

, Volume 176, Issue 1, pp 65–73 | Cite as

Response of heart rate and cloacal ventilation in the bimodally respiring freshwater turtle, Rheodytes leukops, to experimental changes in aquatic PO2

  • Matthew A. Gordos
  • Colin J. Limpus
  • Craig E. Franklin
Original Paper

Abstract

Changes in heart rate (f H) and cloacal ventilation frequency (f C) were investigated in the Fitzroy turtle, Rheodytes leukops, under normoxic (17.85 kPa) and hypoxic (3.79 kPa) conditions at 25°C. Given R. leukops’ high reliance on aquatic respiration via the cloacal bursae, the objective of this study was to examine the effect of varying aquatic PO2 levels upon the expression of a bradycardia in a freely diving, bimodally respiring turtle. In normoxia, mean diving f H and f C for R. leukops remained constant with increasing submergence length, indicating that a bradycardia failed to develop during extended dives of up to 3 days. Alternatively, exposure to aquatic hypoxia resulted in the expression of a bradycardia as recorded by a decreasing mean diving f H with increasing dive duration. The observed bradycardia is attributed to a hypoxic-induced metabolic depression, possibly facilitated by a concurrent decrease in f C. Results suggest that R. leukops alters its strategy from aquatic O2 extraction via cloacal respiration in normoxia to O2 conservation when exposed to aquatic hypoxia for the purpose of extending dive duration. Upon surfacing, a significant tachycardia was observed for R. leukops regardless of aquatic PO2, presumably functioning to rapidly equilibrate blood and tissue gas tensions with alveolar gas to reduce surfacing duration.

Keywords

Rheodytes leukops Turtle Heart rate Bradycardia Aquatic respiration 

Abbreviations

BPM

Beats per minute

VPM

Ventilations per minute

fH

Heart rate (BPM)

fC

Cloacal ventilation rate (VPM)

Notes

Acknowledgements

We wish to thank Les Fletcher and Grant Andrews for help with the design of the piezo film set-up, as well as Gordon Grigg and Robert Gatten Jr. for providing helpful comments on earlier versions of the manuscript. Research was supported by a Large Australian Research Council grant to C.E.F. collection and experimentation on R. leukops was approved by Queensland Parks and Wildlife Service (permit no. C6/000094/02/SAA and WISP00474202) and by the University of Queensland’s Animal Experimentation and Ethics committee (AEEC approval number ZOO/ENT/168/02/URG/PHD).

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Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  • Matthew A. Gordos
    • 1
  • Colin J. Limpus
    • 2
  • Craig E. Franklin
    • 1
  1. 1.School of Integrative BiologyThe University of QueenslandBrisbaneAustralia
  2. 2.Queensland Parks and Wildlife ServiceBrisbaneAustralia

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