Effects of training on forced submersion responses in harbor seals
P. D. Jobsis*,
P. J. Ponganis and
G. L. Kooyman
Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093-0204, USA
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Fig. 1. Mean heart rate (mean ± S.D.) for each of the four seals (S, A, W and L) during five submersions during naive and trained sessions. Seals S, A and W are considered to have adapted to the training protocol and were grouped together for later comparison and analysis. Seal L did not increase its heart rate and was excluded from the habituated group.
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Fig. 2. Heart rate during submersion for all training sessions of seal A. Note the steady increase in heart rate and typical pattern of low heart rate for the first submersion of each session. As training progresses, the heart rate approaches the level found in this animal during unrestrained dives in the holding tank, shown as an interrupted line marked with asterisk.
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Fig. 3. Comparison of two submersions, the fourth of the naive session and the third of the trained session, for seal S. Arrows indicate the start and end of submersions. A spontaneous apnea is shown before submersion during the trained session and is indicated by the solid line. Note that heart rate and muscle blood flow (MBF) are higher and the change in muscle oxygenation (oxygenated hemoglobin and myoglobin, HbO+MbO) is lower during trained submersions. Units for Niroscope data are milli-vanders (mvd), which represent the change in concentration within the observed volume of tissue (see Materials and methods).
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Fig. 4. Representative graph of the Niroscope data obtained during a 3.5 min submersion of seal A during the trained session. Note the slight increase in total Hb (tHb) and decrease in oxygenated hemoglobin and myoglobin (HbO+MbO). Hb+Mb, deoxygenated hemoglobin and myoglobin. Units for Niroscope data are milli-vanders (mvd); see Fig. 3 legend. Arrows indicate the approximate start and end of the submersion.
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Fig. 5. The mean plasma lactate concentration in blood samples from seals during and after naive (filled circles) and trained (open circles) submersions. The cross-hatched area represents a 3.0 min submersion period. Values are means ± S.E.M. (N=15). For simplicity, 3.0 and 3.5 min submersion values are plotted together following the 3.0 min time line.
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Fig. 6. The relationship between muscle blood flow and heart rate over the range of conditions for which these measurements were made. Muscle blood flow is given as a percentage of resting muscle blood flow (%RMBF) prior to submersion. The second-order regression line was drawn using SigmaPlot with mean heart rate and blood flow values for each condition listed (r2=0.999, P<0.05). N, naive; T, trained; S, submerged; R, resting condition before submersion; PS, 1 min period immediately following completion of the submersion. Values are means ± S.D. (N=15).
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Fig. 7. Response of muscle blood flow and heart rate during a 5 min submersion of seal S following completion of the 3 min submersion training. Muscle blood flow is given as a percentage of resting muscle blood flow (%RMBF) prior to submersion. After the standard 3 min of submersion (*), heart rate and muscle blood flow return to the levels typically found during submersion of naive seals. Pulsations in muscle blood flow during the last 2 min correspond to individual heart beats. Arrows indicate the start and end of the 5 min submersion.
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© The Company of Biologists Ltd 2001
