First published online July 20, 2006
Journal of Experimental Biology 209, 2961-2970 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02319
Cardiovascular and haematological responses of Atlantic cod (Gadus morhua) to acute temperature increase
M. J. Gollock1,*,
S. Currie2,
L. H. Petersen1 and
A. K. Gamperl1
1 Ocean Sciences Centre, Memorial University of Newfoundland, St John's, NL,
A1C 5S7, Canada
2 Biology Department, Mount Allison University, 63B York Street, Sackville,
New Brunswick, E4L 1G, Canada
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Fig. 1. Temperature profile at a cod cage-site aquaculture facility (Pool's Cove,
Newfoundland) during the summer of 2003. This trace illustrates how quickly
temperatures can change (especially at the depths where fish congregate at
this time of the year; >5 m). Temperature was recorded at several depths;
however, surface, 5 m and 10 m temperatures profiles only are shown to allow
for clarity of data presentation.
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Fig. 2. (A) Rate of oxygen consumption, (B) heart rate fH, (C)
stroke volume VS and (D) cardiac output of Atlantic cod
acclimated to 10-11°C, and subsequently exposed to an acute temperature
increase (at  1.7°C h-1) until they reached their critical
thermal maximum (CTM). Values are means ± s.e.m. (N=6-9).
*Value significantly different (P<0.05) from the
baseline; horizontal bracket indicates the range of measurements that were not
significantly different from the maximum value.
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Fig. 3. Representative traces of blood flow obtained from an Atlantic cod (A) at
baseline temperature (10.9°C), (B) exhibiting the onset of minor
arrhythmias (17.1°C), (C) experiencing significant and prolonged
arrhythmias (20.4°C) and (D) after losing equilibrium (22.3°C). Data
was collected at 10 Hz. Note: different y-axis scales are used in
each panel.
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Fig. 4. Relationship between oxygen consumption, and (A) heart rate and (B) cardiac
output, when Atlantic cod acclimated to 10-11°C were exposed to an acute
temperature increase of 1.7°C h-1. Open circles represent
data for individual fish; filled circles represent mean values (±
s.e.m.) recorded at particular temperatures. The broken lines define the
linear regressions that were fitted to the individual data (heart rate:
y=2.92x-18.5, r2=0.744; cardiac output:
y=3.55x+16.7, r2=0.759). The solid lines
are third order regressions that were fitted to the mean data to show the
general trends in cardiac parameters with temperature (heart rate:
y=-18.7x+0.4x2+0.0019x3+372.5,
r2=0.986; cardiac output:
y=-20.0x+0.7x2+0.0069x3+242.8,
r2=0.995).
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Fig. 5. In vitro haemoglobin-oxygen binding curves for cod blood incubated
at the fish's acclimation temperature (7°C), or after incubation
temperature was increased to 20 or 24°C. Haematocrit was initially set at
20%, and changes in PO2 were made every 30 min. The lines
were fitted to the data for each temperature using a 4-parameter sigmoidal
function. Six individuals were used to generate each curve. See
Table 2 for statistical
analyses of parameters that define Hb-O2 affinity and binding
capacity.
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Fig. 6. In vitro haemoglobin concentrations in the cod blood used to
generate the haemoglobin-oxygen binding curves presented in
Fig. 5. For the 20 or 24°C
experiments, temperature was increased from 7°C (acclimation temperature)
to these temperatures over a 1 h period. Haematocrit was initially set at 20%,
and changes in PO2 were made every 30 min. Values are
means ± s.e.m. (N=5-6). A two-way ANOVA revealed that
haemoglobin levels at 24°C were significantly (P<0.05) lower
than measured at the other two temperatures.
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© The Company of Biologists Ltd 2006
