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- Title
Response of heart rate and cloacal ventilation in the bimodally respiring freshwater turtle, Rheodytes leukops, to experimental changes in aquatic PO<sub>2</sub>.
- Authors
Gordos, Matthew; Limpus, Colin; Franklin, Craig
- 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.
- Subjects
RHEODYTES leukops; ANIMAL ecophysiology; ANIMAL mechanics; HEART beat; RESPIRATION; VITAL signs; BIOMECHANICS; PHYSIOLOGY
- Publication
Journal of Comparative Physiology B: Biochemical, Systemic & Environmental Physiology, 2006, Vol 176, Issue 1, p65
- ISSN
0174-1578
- Publication type
Article
- DOI
10.1007/s00360-005-0033-z