First published online March 16, 2007
Journal of Experimental Biology 210, 1245-1254 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.02709
Temperature and acid–base balance in the American lobster Homarus americanus
Syed Aman Qadri1,
Joseph Camacho1,
Hongkun Wang2,
Josi R. Taylor3,
Martin Grosell3 and
Mary Kate Worden1,*
1 Department of Neuroscience, University of Virginia, Charlottesville, VA
22908, USA
2 Division of Biostatistics and Epidemiology, University of Virginia,
Charlottesville, VA 22908, USA
3 Marine Biology and Fisheries, Rosenstiel School of Marine and Atmospheric
Sciences, University of Miami, FL 33149, USA
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Fig. 1. Hemolymph pH varies as a function of acclimation temperature. Symbols
represent mean (± s.e.m.) values for pH measured in lobsters acclimated
to the indicated temperatures in artificial seawater in the laboratory (filled
symbols) or to the ambient temperature of natural seawater in Woods Hole (MA,
USA) in February (open symbols, WH) and in Salisbury Cove (ME, USA) in July
(open symbols, SC). Numbers of samples measured under each condition are
indicated. Inset: heart rates (mean ± s.e.m.) averaged over a period of
1 min in quiescent lobsters acclimated in the laboratory to water temperatures
of 4 and 20°C.
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Fig. 2. Hemolymph levels (mean ± s.e.m.) of total CO2,
PCO2, CO 2–3 and HCO
–3 vary with acclimation temperature. *Data are
significantly different at P<0.05 (two-sample independent
t-test). Conversion factor: 1 Pa=9.86x10–6
atm.
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Fig. 3. The acid–base status of the hemolymph in a single lobster changes
rapidly in response to a temperature increase. (A) Hemolymph pH (filled
symbols) repeatedly sampled in a single lobster as the seawater temperature
warmed from 2 to 12°C. (B) Hemolymph PCO2 (open
symbols) measured in the same samples. In both plots the line indicates the
kinetics of the temperature change from 2 to 12°C. Conversion factor: 1
Pa=9.86x10–6 atm.
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Fig. 4. The time course of the change in acid–base status of a population
(N=9) of lobsters abruptly exposed to a temperature change from 4 to
22°C. Symbols represent means ± s.e.m. *Data are significantly
different from those at time 0 at P<0.05. Conversion factor: 1
Pa=9.86x10–6 atm.
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Fig. 5. Davenport diagram illustrating changes in acid–base status (mean
± s.e.m.) over 24 h following an abrupt temperature change from 4 to
22°C. Iso-PCO2 (in µatm) lines are drawn. The
buffer line at time 0 h demonstrates the hemolymph buffering capacity of
H. americanus reported by Rose et al.
(Rose et al., 1998 )
(–6.8 CO2 l–1 pH–1 unit).
Conversion factor: 1 Torr=133.3 Pa.
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Fig. 6. Changes in pH modulate lobster cardiac activity. The middle trace shows a
continuous 10 min tension record of the spontaneous beating of the neurogenic
lobster heart in vitro at 16°C. The pH of the saline perfusing
the heart is indicated below the trace. Upper traces show three 8 s samples of
tension recordings selected from the indicated portions of the 10 min
recording to illustrate changes in the amplitude and frequency of the
heartbeat. All traces are shown with the same vertical amplification. Scale
bar, 2 min.
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Fig. 7. Thermal acclimation alters the temperature dependence of heart rate and
ventilation. Heart and ventilation rates (mean ± s.d.) were measured
simultaneously in single lobsters acclimated to cold (4°C; N=7)
and warm (20°C; N=7) temperatures. (A) Heart rates are
temperature dependent. For warm-acclimated lobsters the temperature-dependent
increase in heart rate (slope=0.0635) is statistically significant
(P=0.0001), whereas for cold-acclimated lobsters it is not
(slope=0.04; P=0.06). The temperature-dependent decrease in heart
rate at temperatures of 20°C and above is significant for both
warm-acclimated and cold-acclimated lobsters (slope=–0.056,
P<0.0001 and slope=–0.036, P<0.0001,
respectively). (B) Ventilation rate increases as a function of temperature up
to 20°C. For both warm- and cold-acclimated lobsters the increase in
ventilation at temperatures  20°C is statistically significant
(slope=0.1136; P<0.0001 for warm-acclimated lobsters;
slope=0.0235, P=0.0001 for cold-acclimated lobsters). At temperatures
>20°C ventilation decreases significantly in warm-acclimated lobsters
(slope=–0.052, P=0.0001). In cold-acclimated lobsters, the
temperature dependence of ventilation decreases at temperatures >20°C,
although not to a significant extent (slope=–0.09, P=0.413).
*Data from cold- and warm-acclimated lobsters are significantly different at
P<0.05. Insets show samples of traces from ventilation and heart
recordings in warm- and cold-acclimated lobsters at 2 and 20°C. Values of
N are  5, except as follows: heart rate in cold-acclimated animals
at 30°C (N=1), heart rate in warm-acclimated animals at 26°C
(N=4) and 30°C (N=2), ventilation in cold-acclimated
animals at 6°C (N=3), at 22°C (N=4), at 24°C
(N=4), at 26°C (N=1) and at 28°C (N=1), and
ventilation in warm-acclimated animals at 2°C (N=4), at 28°C
(N=4) and at 30°C (N=2).
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© The Company of Biologists Ltd 2007
