On-line venous oxygen tensions in rainbow trout during graded exercise at two acclimation temperatures
A. P. Farrell* and
S. M. Clutterham
Department of Biological Sciences, Simon Fraser University, 8888
University Drive, Burnaby, British Columbia, V5A 1S6, Canada
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Fig. 1. On-line venous blood oxygen partial pressure
(PvO2) measurements in the ductus Cuvier of
cold-acclimated and warm-acclimated rainbow trout (A,D) during the
post-operative recovery period, (B,E) following the first swim test and (C,F)
following the second swim test. Mean values (black line; grey lines are the
S.E.M.) were derived by pooling data for all fish as a function of time. 1
torr=133.3 Pa.
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Fig. 2. Mean venous blood oxygen partial pressure (PVO2)
measurements in the ductus Cuvier for cold-acclimated and warm-acclimated
rainbow trout during graded exercise. Values were derived from periods of
steady-state swimming at each velocity increment. To permit comparisons
between the cold- and warm-acclimated fish, swimming velocity is expressed as
a percentage of the critical swimming speed (%Ucrit).
Horizontal and vertical bars indicate the S.E.M. Dissimilar letters represent
statistical difference within a swim. Values without letters were not included
in the repeated-measures analysis of variance (ANOVA). Asterisks represent
significant difference between the acclimation temperatures at similar
%Ucrit. The inset presents the data for the first
(habituation) swim. 1 torr=133.3 Pa.
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Fig. 3. Examples of on-line venous blood oxygen partial pressure
(PVO2) measurements in the ductus Cuvier of (A,B)
cold-acclimated and (C,D) warm-acclimated rainbow trout during the first
(habituation) and second (critical speed) swim tests. The incremental
increases in water velocity are also shown for reference. The symbols `f' and
`b' refer to fighting and burst-and-coast swimming behaviours, respectively,
which were visually observed. 1 torr=133.3 Pa.
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Fig. 4. A summary of the effects of unsteady (fighting and burst-and-coast)
swimming behaviours on the venous blood oxygen partial pressure
(PvO2). The minimum
PvO2 observed at 100% critical swimming speed
(Ucrit) was assigned a value, and the minimum
PvO2 as a result of the unsteady swimming
behaviour was expressed as a percentage. For clarity, only
PvO2 values within 60% of the threshold are
presented.
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© The Company of Biologists Ltd 2003
) at the routine levels indicated.
Because cardiac output would have increased at Ucrit, the
curve underestimates the true venous oxygen delivery. The open symbols, which
account for the effect of a 2.1-fold increase in