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First published online January 17, 2007
Journal of Experimental Biology 210, 421-431 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.02653

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Effects of extracellular changes on spontaneous heart rate of normoxia- and anoxia-acclimated turtles (Trachemys scripta)

Jonathan A. W. Stecyk^1,* and Anthony P. Farrell²

¹ Department of Zoology, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
² Faculty of Land and Food Systems and Department of Zoology, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada

View larger version (9K): [in this window] [in a new window]   Fig. 1. Spontaneous heart rate (fH) of 5°C, and 21°C, normoxia- and anoxia-acclimated control preparations during the control experiments. Adrenaline concentration (nmol l–1) is indicated in parentheses. Significant differences (P<0.05) in fH among time points within an experimental group are indicated by different letters. Values are means ± s.e.m.; N=6 except for the 5°C normoxia-acclimated experimental group where N=5, unless otherwise indicated in parentheses.

View larger version (21K): [in this window] [in a new window]   Fig. 2. Spontaneous heart rate fH of 21°C normoxia- and anoxia-acclimated right-atrial preparations during exposure to various saline solutions devised to simulate or reverse the changes occurring in turtle blood plasma during 6 h of anoxic submergence, in the presence of 1 or 10 nmol l–1 tonic adrenaline (indicated in parentheses). Exposure order for normoxia-acclimated preparations was as given in the figure, reading from left-to-right, whereas exposure order for anoxia-acclimated preparations was as reading from right-to-left. Significant differences (P<0.05) in fH among saline solutions within an experimental group are indicated by different letters. Significant differences (P<0.05) in fH from a comparable Control protocol fH. Significant differences (P<0.05) in fH between 1 nmol l–1 and 10 nmol l–1 tonic adrenaline groups within an acclimation condition (i.e. normoxia- or anoxia-acclimated). *Significant difference (P<0.05) in fH between normoxia- and anoxia-acclimated preparations (of the same level of tonic adrenergic stimulation) under simulated in vivo normoxic or simulated in vivo anoxic conditions. Values are means ± s.e.m.; N=6 in the 1 nmol l–1 tonic adrenaline normoxia- and anoxia-acclimated groups, 5 in the 10 nmol l–1 tonic adrenaline normoxia-acclimated group and 6 in the 10 nmol l–1 tonic adrenaline anoxia-acclimated group.

View larger version (12K): [in this window] [in a new window]   Fig. 3. Spontaneous fH of 5°C, normoxia- and anoxia-acclimated right-atrial preparations during exposure to various saline solutions devised to simulate or reverse the changes occurring in turtle blood plasma during 14 days of anoxic submergence. Exposure order for normoxia-acclimated preparations was as given in the figure, reading from left-to-right, whereas exposure order for anoxia-acclimated preparations was as reading from right-to-left. Significant differences (P<0.05) in fH among saline solutions within an experimental group are indicated by different letters. Significant differences (P<0.05) in fH from a comparable Control protocol fH. *Significant difference (P<0.05) in fH between normoxia- and anoxia-acclimated preparations under simulated in vivo normoxic or simulated in vivo anoxic conditions. Values are means ± s.e.m.; N=6 in both experimental groups.